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Twesigomwe D, Drögemöller BI, Wright GEB, Adebamowo C, Agongo G, Boua PR, Matshaba M, Paximadis M, Ramsay M, Simo G, Simuunza MC, Tiemessen CT, Lombard Z, Hazelhurst S. Characterization of CYP2B6 and CYP2A6 Pharmacogenetic Variation in Sub-Saharan African Populations. Clin Pharmacol Ther 2024; 115:576-594. [PMID: 38049200 DOI: 10.1002/cpt.3124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 11/16/2023] [Indexed: 12/06/2023]
Abstract
Genetic variation in CYP2B6 and CYP2A6 is known to impact interindividual response to antiretrovirals, nicotine, and bupropion, among other drugs. However, the full catalogue of clinically relevant pharmacogenetic variants in these genes is yet to be established, especially across African populations. This study therefore aimed to characterize the star allele (haplotype) distribution in CYP2B6 and CYP2A6 across diverse and understudied sub-Saharan African (SSA) populations. We called star alleles from 961 high-depth full genomes using StellarPGx, Aldy, and PyPGx. In addition, we performed CYP2B6 and CYP2A6 star allele frequency comparisons between SSA and other global biogeographical groups represented in the new 1000 Genomes Project high-coverage dataset (n = 2,000). This study presents frequency information for star alleles in CYP2B6 (e.g., *6 and *18; frequency of 21-47% and 2-19%, respectively) and CYP2A6 (e.g., *4, *9, and *17; frequency of 0-6%, 3-10%, and 6-20%, respectively), and predicted phenotypes (for CYP2B6), across various African populations. In addition, 50 potentially novel African-ancestry star alleles were computationally predicted by StellarPGx in CYP2B6 and CYP2A6 combined. For each of these genes, over 4% of the study participants had predicted novel star alleles. Three novel star alleles in CYP2A6 (*54, *55, and *56) and CYP2B6 apiece, and several suballeles were further validated via targeted Single-Molecule Real-Time resequencing. Our findings are important for informing the design of comprehensive pharmacogenetic testing platforms, and are highly relevant for personalized medicine strategies, especially relating to antiretroviral medication and smoking cessation treatment in Africa and the African diaspora. More broadly, this study highlights the importance of sampling diverse African ethnolinguistic groups for accurate characterization of the pharmacogene variation landscape across the continent.
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Affiliation(s)
- David Twesigomwe
- Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Division of Human Genetics, National Health Laboratory Service, and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Britt I Drögemöller
- Department of Biochemistry and Medical Genetics, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Galen E B Wright
- Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Winnipeg Health Sciences Centre and Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Clement Adebamowo
- Institute for Human Virology, Abuja, Nigeria
- Division of Cancer Epidemiology, Department of Epidemiology and Public Health, and the Marlene and Stewart Greenebaum Comprehensive Cancer Centre, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Godfred Agongo
- Navrongo Health Research Centre, Ghana Health Service, Navrongo, Ghana
- Department of Biochemistry and Forensic Sciences, School of Chemical and Biochemical Sciences, C.K. Tedam University of Technology and Applied Sciences, Navrongo, Ghana
| | - Palwendé R Boua
- Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Clinical Research Unit of Nanoro, Institut de Recherche en Sciences de la Santé, Nanoro, Burkina Faso
| | - Mogomotsi Matshaba
- Botswana-Baylor Children's Clinical Centre of Excellence, Gaborone, Botswana
- Retrovirology, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
| | - Maria Paximadis
- Centre for HIV and STIs, National Institute for Communicable Diseases, National Health Laboratory Services and Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
| | - Michèle Ramsay
- Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Division of Human Genetics, National Health Laboratory Service, and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Gustave Simo
- Molecular Parasitology and Entomology Unit, Department of Biochemistry, Faculty of Science, University of Dschang, Dschang, Cameroon
| | - Martin C Simuunza
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Caroline T Tiemessen
- Centre for HIV and STIs, National Institute for Communicable Diseases, National Health Laboratory Services and Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Zané Lombard
- Division of Human Genetics, National Health Laboratory Service, and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Scott Hazelhurst
- Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- School of Electrical and Information Engineering, University of the Witwatersrand, Johannesburg, South Africa
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Medaglio D, Bilker WB, Han X, Merlin JS, Plankey M, Martin J, Crane HM, Hojat LS, Bamford L, Schnoll R, Tyndale RF, Ashare RL, Gross R. Nicotine Metabolite Ratio Decreases After Switching Off Efavirenz-Based Therapy in People With HIV Who Smoke. Clin Pharmacol Ther 2024; 115:80-85. [PMID: 37787039 PMCID: PMC10752215 DOI: 10.1002/cpt.3068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 09/14/2023] [Indexed: 10/04/2023]
Abstract
Rates of cigarette smoking in people with HIV (PWH) are two to three times higher than in people without HIV. Nicotine is metabolized by CYP2A6 and the nicotine metabolite ratio (NMR; 3-hydroxycotinine/cotinine) is a measure of nicotine clearance. Higher NMR has been observed in PWH and is associated with lower quit rates. Efavirenz, a mainstay antiretroviral therapy (ART) globally, partially upregulates its own metabolism through CYP2A6. We hypothesized that efavirenz also upregulates nicotine metabolism by CYP2A6, resulting in a higher NMR, and switching to non-efavirenz ART would decrease the NMR, potentially leading to improved quit rates. We compared the NMR during and after efavirenz use among PWH in a longitudinal, multisite cohort. Eligibility criteria included: (i) active cigarette smoking, (ii) ART switched from efavirenz-based to non-efavirenz-based regimen, (iii) plasma available at pre- and post-ART switch, and (iv) viral suppression during study period. Plasma cotinine and 3-hydroxycotinine were measured by liquid chromatography-tandem mass spectrometry. T-tests compared the NMR on and off efavirenz. Samples were collected between 2010 and 2019 in 72 PWH. The mean NMR difference after switching to a non-efavirenz-based regimen was -0.24 (SD: 0.37, P < 0.001); 44 PWH had at least a 0.1 decrease in NMR. Effect modification by race was present; Black PWH had a larger mean decrease. Our findings suggest that previously observed higher NMR among PWH may be due to direct pharmacologic effects of ART. Assessing the effect of ART on the NMR suggests that avoiding nicotine metabolism inducers could potentially increase quit rates.
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Affiliation(s)
- Dominique Medaglio
- Department of Epidemiology, Biostatistics & Informatics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Warren B. Bilker
- Department of Epidemiology, Biostatistics & Informatics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Xiaoyan Han
- Department of Epidemiology, Biostatistics & Informatics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jessica S. Merlin
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Michael Plankey
- Department of Medicine, Georgetown University, Washington, DC, USA
| | - Jeffrey Martin
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, USA
| | - Heidi M. Crane
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Leila S. Hojat
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Laura Bamford
- Department of Medicine, University of California San Diego, San Diego, California, USA
| | - Robert Schnoll
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Rachel F. Tyndale
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada
- The Centre for Addiction and Mental Health, Toronto, Ontario, Canada
| | - Rebecca L. Ashare
- Department of Psychology, State University of New York at Buffalo, Buffalo, New York, USA
| | - Robert Gross
- Department of Epidemiology, Biostatistics & Informatics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Yadav A, Kesharwani A, Chaurasia DK, Katara P. Mining of molecular insights of CYP2A6 and its variants complex with coumarin (CYP2A6*-coumarin) using molecular dynamics simulation. J Biomol Struct Dyn 2023; 41:4081-4092. [PMID: 35427216 DOI: 10.1080/07391102.2022.2062785] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 04/02/2022] [Indexed: 10/18/2022]
Abstract
CYP2A6 is a very important enzyme that plays a crucial role in nicotine compounds and is responsible for the metabolism of more than 3% drugs of total metabolized drugs by the CYP family and reported as one of very important pharmacogenes. CYP2A6 is highly polymorphic in nature and reported with more than 40 variants, most of these variants are SNPs originated and population specific. It has been well observed and reported that the presence of these population-specific non-synonymous SNPs in CYP2A6 alters the rate of drug metabolism and as a functional consequence, drugs produce an abnormal response. Though genomics and pharmacogenomics studies are there, very less is known about the structural effects of these SNPs on molecular-interaction and folding of CYP2A6. To fill the knowledge gap, SNPs based four variants, i.e., CYP2A6*2, CYP2A6*18, CYP2A6*21, and CYP2A6*35, which are frequently reported in the South Asian population, were considered for the study. Coumarin (DB04665), a well reported drug, is considered as a model substance, and the effect of all four variants on 'CYP2A6*-coumarin' complex was studied. MD simulation-based analysis (at 200 ns) was performed and comparative analysis with respect to wild type 'CYP2A6-coumarin' complex was done. Though observation didn't find any global effect on complete complex but found some crucial minor-local alteration in interaction and folding process. It is assumed that the change due to SNPs in the single amino acid did not bring global change in physiochemical properties of CYP2A6* but caused local-trivial changes which are very crucial for its metabolic activity.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Anamika Yadav
- Computational omics Lab, Centre of Bioinformatics, University of Allahabad, Prayagraj, India
| | - Akanksha Kesharwani
- Computational omics Lab, Centre of Bioinformatics, University of Allahabad, Prayagraj, India
- Supercomputing Facility for Bioinformatics and Computational Biology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India
| | - Dheeraj Kumar Chaurasia
- Supercomputing Facility for Bioinformatics and Computational Biology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India
| | - Pramod Katara
- Computational omics Lab, Centre of Bioinformatics, University of Allahabad, Prayagraj, India
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Langlois AW, El-Boraie A, Fukunaga K, Mushiroda T, Kubo M, Lerman C, Knight J, Scherer SE, Chenoweth MJ, Tyndale RF. Accuracy and applications of sequencing and genotyping approaches for CYP2A6 and homologous genes. Pharmacogenet Genomics 2022; 32:159-172. [PMID: 35190513 PMCID: PMC9081136 DOI: 10.1097/fpc.0000000000000466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES We evaluated multiple genotyping/sequencing approaches in a homologous region of chromosome 19, and investigated associations of two common 3'-UTR CYP2A6 variants with activity in vivo. METHODS Individuals (n = 1704) of European and African ancestry were phenotyped for the nicotine metabolite ratio (NMR), an index of CYP2A6 activity, and genotyped/sequenced using deep amplicon exon sequencing, SNP array, genotype imputation and targeted capture sequencing. Amplicon exon sequencing was the gold standard to which other methods were compared within-individual for CYP2A6, CYP2A7, CYP2A13, and CYP2B6 exons to identify highly discordant positions. Linear regression models evaluated the association of CYP2A6*1B and rs8192733 genotypes (coded additively) with logNMR. RESULTS All approaches were ≤2.6% discordant with the gold standard; discordant calls were concentrated at few positions. Fifteen positions were discordant in >10% of individuals, with 12 appearing in regions of high identity between homologous genes (e.g. CYP2A6 and CYP2A7). For six, allele frequencies in our study and online databases were discrepant, suggesting errors in online sources. In the European-ancestry group (n = 935), CYP2A6*1B and rs8192733 were associated with logNMR (P < 0.001). A combined model found main effects of both variants on increasing logNMR. Similar trends were found in those of African ancestry (n = 506). CONCLUSION Multiple genotyping/sequencing approaches used in this chromosome 19 region contain genotyping/sequencing errors, as do online databases. Gene-specific primers and SNP array probes must consider gene homology; short-read sequencing of related genes in a single reaction should be avoided. Using improved sequencing approaches, we characterized two gain-of-function 3'-UTR variants, including the relatively understudied rs8192733.
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Affiliation(s)
- Alec W.R. Langlois
- Department of Pharmacology & Toxicology, University of Toronto; 1 King’s College Circle, Toronto, ON, M5S 1A8, Canada. Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health 100 Stokes Street, Toronto, ON, M6J 1H4, Canada
| | - Ahmed El-Boraie
- Department of Pharmacology & Toxicology, University of Toronto; 1 King’s College Circle, Toronto, ON, M5S 1A8, Canada. Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health 100 Stokes Street, Toronto, ON, M6J 1H4, Canada
| | - Koya Fukunaga
- Center for Integrative Medical Sciences, RIKEN; 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
| | - Taisei Mushiroda
- Center for Integrative Medical Sciences, RIKEN; 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
| | - Michiaki Kubo
- Center for Integrative Medical Sciences, RIKEN; 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
| | - Caryn Lerman
- Department of Psychiatry and USC Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Avenue, Cancer Center, Los Angeles, CA, 90089, United States
| | - Jo Knight
- Data Science Institute and Lancaster University Medical School, Lancaster, UK
- Department of Psychiatry, University of Toronto; 250 College Street, Toronto, ON, M5T 1R8, Canada
| | - Steven E. Scherer
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
| | - Meghan J. Chenoweth
- Department of Pharmacology & Toxicology, University of Toronto; 1 King’s College Circle, Toronto, ON, M5S 1A8, Canada. Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health 100 Stokes Street, Toronto, ON, M6J 1H4, Canada
| | - Rachel F. Tyndale
- Department of Pharmacology & Toxicology, University of Toronto; 1 King’s College Circle, Toronto, ON, M5S 1A8, Canada. Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health 100 Stokes Street, Toronto, ON, M6J 1H4, Canada
- Department of Psychiatry, University of Toronto; 250 College Street, Toronto, ON, M5T 1R8, Canada
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Deciphering Structural Alterations Associated with Activity Reductions of Genetic Polymorphisms in Cytochrome P450 2A6 Using Molecular Dynamics Simulations. Int J Mol Sci 2021; 22:ijms221810119. [PMID: 34576282 PMCID: PMC8469730 DOI: 10.3390/ijms221810119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 12/04/2022] Open
Abstract
Cytochrome P450 (CYP) 2A6 is a monooxygenase involved in the metabolism of various endogenous and exogenous chemicals, such as nicotine and therapeutic drugs. The genetic polymorphisms in CYP2A6 are a cause of individual variation in smoking behavior and drug toxicities. The enzymatic activities of the allelic variants of CYP2A6 were analyzed in previous studies. However, the three-dimensional structures of the mutants were not investigated, and the mechanisms underlying activity reduction remain unknown. In this study, to investigate the structural changes involved in the reduction in enzymatic activities, we performed molecular dynamics simulations for ten allelic mutants of CYP2A6. For the calculated wild type structure, no significant structural changes were observed in comparison with the experimental structure. On the other hand, the mutations affected the interaction with heme, substrates, and the redox partner. In CYP2A6.44, a structural change in the substrate access channel was also observed. Those structural effects could explain the alteration of enzymatic activity caused by the mutations. The results of simulations provide useful information regarding the relationship between genotype and phenotype.
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El-Boraie A, Tanner JA, Zhu AZX, Claw KG, Prasad B, Schuetz EG, Thummel KE, Fukunaga K, Mushiroda T, Kubo M, Benowitz NL, Lerman C, Tyndale RF. Functional characterization of novel rare CYP2A6 variants and potential implications for clinical outcomes. Clin Transl Sci 2021; 15:204-220. [PMID: 34476898 PMCID: PMC8742641 DOI: 10.1111/cts.13135] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/23/2021] [Accepted: 07/24/2021] [Indexed: 11/28/2022] Open
Abstract
CYP2A6 activity, phenotyped by the nicotine metabolite ratio (NMR), is a predictor of several smoking behaviors, including cessation and smoking‐related disease risk. The heritability of the NMR is 60–80%, yet weighted genetic risk scores (wGRSs) based on common variants explain only 30–35%. Rare variants (minor allele frequency <1%) are hypothesized to explain some of this missing heritability. We present two targeted sequencing studies where rare protein‐coding variants are functionally characterized in vivo, in silico, and in vitro to examine this hypothesis. In a smoking cessation trial, 1687 individuals were sequenced; characterization measures included the in vivo NMR, in vitro protein expression, and metabolic activity measured from recombinant proteins. In a human liver bank, 312 human liver samples were sequenced; measures included RNA expression, protein expression, and metabolic activity from extracted liver tissue. In total, 38 of 47 rare coding variants identified were novel; characterizations ranged from gain‐of‐function to loss‐of‐function. On a population level, the portion of NMR variation explained by the rare coding variants was small (~1%). However, upon incorporation, the accuracy of the wGRS was improved for individuals with rare protein‐coding variants (i.e., the residuals were reduced), and approximately one‐third of these individuals (12/39) were re‐assigned from normal to slow metabolizer status. Rare coding variants can alter an individual’s CYP2A6 activity; their integration into wGRSs through precise functional characterization is necessary to accurately assess clinical outcomes and achieve precision medicine for all. Investigation into noncoding variants is warranted to further explain the missing heritability in the NMR.
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Affiliation(s)
- Ahmed El-Boraie
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON, Canada.,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health and Division of Brain and Therapeutics, Toronto, ON, Canada
| | | | - Andy Z X Zhu
- Department of Quantitative Translational Sciences, Takeda Pharmaceuticals, Cambridge, Massachusetts, USA
| | - Katrina G Claw
- Division of Biomedical Informatics and Personalized Medicine, University of Colorado, Aurora, Colorado, USA
| | - Bhagwat Prasad
- Department of Pharmaceutical Sciences, Washington State University, Spokane, Washington, USA
| | - Erin G Schuetz
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Kenneth E Thummel
- Department of Pharmaceutics, University of Washington, Seattle, Washington, USA
| | - Koya Fukunaga
- Center for Integrative Medical Sciences, RIKEN, Yokohama, Japan
| | | | - Michiaki Kubo
- Center for Integrative Medical Sciences, RIKEN, Yokohama, Japan
| | - Neal L Benowitz
- Clinical Pharmacology Research Program, Division of Cardiology, Department of Medicine and Center for Tobacco Control Research and Education, University of California San Francisco, San Francisco, California, USA
| | - Caryn Lerman
- Department of Psychiatry, USC Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California, USA
| | - Rachel F Tyndale
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON, Canada.,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health and Division of Brain and Therapeutics, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
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Murphy SE. Biochemistry of nicotine metabolism and its relevance to lung cancer. J Biol Chem 2021; 296:100722. [PMID: 33932402 PMCID: PMC8167289 DOI: 10.1016/j.jbc.2021.100722] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/26/2021] [Accepted: 04/27/2021] [Indexed: 12/27/2022] Open
Abstract
Nicotine is the key addictive constituent of tobacco. It is not a carcinogen, but it drives smoking and the continued exposure to the many carcinogens present in tobacco. The investigation into nicotine biotransformation has been ongoing for more than 60 years. The dominant pathway of nicotine metabolism in humans is the formation of cotinine, which occurs in two steps. The first step is cytochrome P450 (P450, CYP) 2A6–catalyzed 5′-oxidation to an iminium ion, and the second step is oxidation of the iminium ion to cotinine. The half-life of nicotine is longer in individuals with low P450 2A6 activity, and smokers with low activity often decrease either the intensity of their smoking or the number of cigarettes they use compared with those with “normal” activity. The effect of P450 2A6 activity on smoking may influence one's tobacco-related disease risk. This review provides an overview of nicotine metabolism and a summary of the use of nicotine metabolite biomarkers to define smoking dose. Some more recent findings, for example, the identification of uridine 5′-diphosphoglucuronosyltransferase 2B10 as the catalyst of nicotine N-glucuronidation, are discussed. We also describe epidemiology studies that establish the contribution of nicotine metabolism and CYP2A6 genotype to lung cancer risk, particularly with respect to specific racial/ethnic groups, such as those with Japanese, African, or European ancestry. We conclude that a model of nicotine metabolism and smoking dose could be combined with other lung cancer risk variables to more accurately identify former smokers at the highest risk of lung cancer and to intervene accordingly.
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Affiliation(s)
- Sharon E Murphy
- Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA.
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Nollen NL, Ahluwalia JS, Sanderson Cox L, Okuyemi K, Lawrence D, Samuels L, Benowitz NL. Assessment of Racial Differences in Pharmacotherapy Efficacy for Smoking Cessation: Secondary Analysis of the EAGLES Randomized Clinical Trial. JAMA Netw Open 2021; 4:e2032053. [PMID: 33464316 PMCID: PMC7816102 DOI: 10.1001/jamanetworkopen.2020.32053] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
IMPORTANCE Understanding Black vs White differences in pharmacotherapy efficacy and the underlying reasons is critically important to reducing tobacco-related health disparities. OBJECTIVE To compare pharmacotherapy efficacy and examine variables to explain Black vs White differences in smoking abstinence. DESIGN, SETTING, AND PARTICIPANTS This study is a secondary analysis of the Evaluating Adverse Events in a Global Smoking Cessation Study (EAGLES) double-blind, placebo-controlled, randomized clinical trial, which took place at clinical trial centers, academic centers, and outpatient clinics in 29 states in the US. US Black and White smokers who smoked 10 or more cigarettes per day with and without psychiatric comorbidity were enrolled between November 2011 and January 2015. Data analysis was performed from July 2019 to January 2020. INTERVENTIONS Participants were randomized (1:1:1:1) in a double-blind, triple-dummy, placebo- and active-controlled (nicotine patch) trial of varenicline and bupropion for 12 weeks with follow-up through week 24. MAIN OUTCOMES AND MEASURES Biochemically verified continuous cigarette abstinence rate (CAR) from weeks 9 to 24. Baseline, postbaseline treatment, and safety characteristics were examined as variables to explain race differences in abstinence. RESULTS Of the 1065 Black smokers enrolled, 255 were randomized to receive varenicline, 259 received bupropion, 286 received nicotine replacement therapy (NRT [ie, nicotine patch]), and 265 received placebo. Among the 3044 White smokers enrolled, 778 were randomized to receive varenicline, 769 received bupropion, 738 received NRT, and 759 received placebo. Participants were predominantly female (614 Black [57.7%] and 1786 White [58.7%] women) and heavy smokers (mean [SD] cigarettes per day, 18.2 [7.9] for Black and 20.0 [7.5] for White smokers), with a mean (SD) age of 47.2 (11.2) years for Black and 46.5 (12.7) years for White participants. Treatment and race were associated with CAR for weeks 9 to 24. The CAR was 4.9% lower for Black vs White participants (odds ratio [OR], 0.53; 95% CI, 0.41-0.69; P < .001); differences were found across all treatments. Pooling psychiatric and nonpsychiatric cohorts, varenicline (OR, 2.63; 95% CI, 1.90-3.63; P < .001), bupropion (OR, 1.75; 95% CI, 1.25-2.46; P = .001), and NRT (OR, 1.52; 95% CI, 1.07-2.16; P = .02) had greater efficacy than placebo for White participants. Only varenicline (OR, 2.63; 95% CI, 1.26-5.48; P = .01) had greater efficacy than placebo for Black participants. Baseline, postbaseline, and safety characteristics differed by race, but these variables did not eliminate the association of race with CAR. Black participants had 49% reduced odds of CAR for weeks 9 to 24 compared with White participants in the adjusted model (OR, 0.51; 95% CI, 0.39-0.66; P < .001). CONCLUSIONS AND RELEVANCE Black and White smokers achieved the highest rate of abstinence while taking varenicline, suggesting that it is the best first-line therapy for these groups. However, Black smokers were less responsive to all therapies, including placebo. Understanding variables (eg, socioeconomic or biological) beyond those may lead to improved treatment outcomes for Black smokers. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT01456936.
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Affiliation(s)
- Nicole L. Nollen
- Department of Population Health, University of Kansas School of Medicine, Kansas City
| | - Jasjit S. Ahluwalia
- Alpert Medical School, Department of Behavioral and Social Sciences, Brown University School of Public Health, Providence, Rhode Island
- Alpert Medical School, Department of Medicine, Brown University School of Public Health, Providence, Rhode Island
| | - Lisa Sanderson Cox
- Department of Population Health, University of Kansas School of Medicine, Kansas City
| | - Kolawole Okuyemi
- Department of Family and Preventive Medicine, The University of Utah School of Medicine, Salt Lake City
| | | | | | - Neal L. Benowitz
- Department of Medicine, Bioengineering, and Therapeutic Sciences, University of California, San Francisco
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Jeon CY, Feldman R, Pendergast FJ, AlKaade S, Brand RE, Guda N, Sandhu BS, Singh VK, Wilcox CM, Slivka A, Whitcomb DC, Yadav D. Divergent trends in lifetime drinking and smoking between Black and White Americans diagnosed with chronic pancreatitis. Pancreatology 2020; 20:1667-1672. [PMID: 33132046 PMCID: PMC7737506 DOI: 10.1016/j.pan.2020.10.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/08/2020] [Accepted: 10/08/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND/OBJECTIVES Black Americans are at increased risk of chronic pancreatitis (CP) compared to their White counterparts. We aimed to describe the race-specific smoking history and lifetime drinking in patients diagnosed with CP. METHODS We analyzed data on 334 Black and White CP participants of the North American Pancreatitis Study 2 Continuation and Validation Study and Ancillary Study. Lifetime drinking history and lifetime smoking history were collected through in-person interviews. Intensity, frequency, duration and current status of drinking and smoking were compared between Black and White CP participants, stratified by physician-defined alcohol etiology. In addition, drinking levels at each successive decades in life (20s, 30s, 40s) were compared by race and graphically portrayed as heat diagrams. RESULTS Among patients with alcoholic CP, current smoking levels were not different by race (67-70%), but a smaller proportion of Black patients reported having smoked 1 or more packs per day in the past (32%) as compared to White patients (58%, p < 0.0001). Black patients were more likely to report current consumption of alcohol (31%), as opposed to White patients (17%, p = 0.016). Black patients also reported more intense drinking at age 35 and 45 years as compared to White patients, while age at CP onset were similar between the two groups. CONCLUSION We found more intense drinking but less intense smoking history in Black CP patients as compared to White CP patients. Effective alcohol abstinence and smoking cessation program with sustained impact are needed in CP patients.
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Affiliation(s)
- Christie Y. Jeon
- Cedars Sinai Cancer, Cedars-Sinai Medical Center, Los Angeles, CA,Department of Epidemiology, UCLA Fielding School of Public Health, Los Angeles, CA
| | - Robert Feldman
- Center for Research on Healthcare Data Center, University of Pittsburgh, Pittsburgh, PA
| | | | | | - Randall E. Brand
- Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Nalini Guda
- Aurora St. Luke's Medical Center, Milwaukee, WI
| | | | - Vikesh K. Singh
- Pancreatitis Center, Division of Gastroenterology, Johns Hopkins Medical Institutions, Baltimore, MD
| | - C. Mel Wilcox
- Division of Gastroenterology and Hepatology, University of Alabama Birmingham, AL
| | - Adam Slivka
- Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - David C. Whitcomb
- Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Dhiraj Yadav
- Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA
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10
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Nollen NL, Mayo MS, Sanderson Cox L, Benowitz NL, Tyndale RF, Ellerbeck EF, Scheuermann TS, Ahluwalia JS. Factors That Explain Differences in Abstinence Between Black and White Smokers: A Prospective Intervention Study. J Natl Cancer Inst 2020; 111:1078-1087. [PMID: 30657926 DOI: 10.1093/jnci/djz001] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 10/03/2018] [Accepted: 01/02/2019] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Black-white differences in smoking abstinence are not well understood. This trial sought to confirm previously reported differences in quitting between blacks and whites and to identify factors underlying this difference. METHODS During enrollment, 224 black and 225 white low-income smokers were stratified on race and within race on age and sex to ensure balance on these factors known to impact abstinence. The intervention included varenicline for 12 weeks and six guideline-based smoking cessation counseling sessions. The primary endpoint was cotinine-verified 7-day point prevalence smoking abstinence at week 26. A priori socioeconomic, smoking, treatment process (eg, treatment utilization, side effects, withdrawal relief), psychosocial, and biological factors were assessed to investigate race differences in abstinence. Unadjusted odds ratios (OR) were used to compare abstinence between blacks and whites. Adjusted odds ratios from logistic regression models were used to examine predictors of abstinence. All statistical tests were two-sided. RESULTS Blacks were less likely to achieve abstinence at week 26 (14.3% vs 24.4%, OR = 0.51, 95% confidence interval [CI] = 0.32 to 0.83, P = .007). Utilizing best subsets logistic regression, five factors associated with race jointly predicted abstinence: home ownership (yes/no, OR = 3.03, 95% CI = 1.72 to 5.35, P < .001), study visits completed (range = 0-6, OR = 2.81, 95% CI = 1.88 to 4.20, P < .001), income (household member/$1000, OR = 1.03, 95% CI = 1.01 to 1.06, P = .02), plasma cotinine (per 1 ng/mL, OR = 0.997, 95% CI = 0.994 to 0.999, P = .002), and neighborhood problems (range = 10-30, OR = 0.88, 95% CI = 0.81 to 0.96, P = .003). CONCLUSIONS The race difference in abstinence was fully explained by lack of home ownership, lower income, greater neighborhood problems, higher baseline cotinine, and higher visit completion, which were disproportionately represented among blacks. Findings illuminate factors that make it harder for blacks in the United States to quit smoking relative to whites and provide important areas for future studies to reduce tobacco-related health disparities.
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11
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Wang D, Lu R, Rempala G, Sadee W. Ligand-Free Estrogen Receptor α (ESR1) as Master Regulator for the Expression of CYP3A4 and Other Cytochrome P450 Enzymes in the Human Liver. Mol Pharmacol 2019; 96:430-440. [PMID: 31399483 PMCID: PMC6724575 DOI: 10.1124/mol.119.116897] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 08/01/2019] [Indexed: 12/25/2022] Open
Abstract
Cytochrome P450 3A4 isoform (CYP3A4) transcription is controlled by hepatic transcription factors (TFs), but how TFs dynamically interact remains uncertain. We hypothesize that several TFs form a regulatory network with nonlinear, dynamic, and hierarchical interactions. To resolve complex interactions, we have applied a computational approach for estimating Sobol's sensitivity indices (SSI) under generalized linear models to existing liver RNA expression microarray data (GSE9588) and RNA-seq data from genotype-tissue expression (GTEx), generating robust importance ranking of TF effects and interactions. The SSI-based analysis identified TFs and interacting TF pairs, triplets, and quadruplets involved in CYP3A4 expression. In addition to known CYP3A4 TFs, estrogen receptor α (ESR1) emerges as key TF with the strongest main effect and as the most frequently included TF interacting partner. Model predictions were validated using small interfering RNA (siRNA)/short hairpin RNA (shRNA) gene knockdown and clustered regularly interspaced short palindromic repeats (CRISPR)-mediated transcriptional activation of ESR1 in biliary epithelial Huh7 cells and human hepatocytes in the absence of estrogen. Moreover, ESR1 and known CYP3A4 TFs mutually regulate each other. Detectable in both male and female hepatocytes without added estrogen, the results demonstrate a role for unliganded ESR1 in CYP3A4 expression consistent with unliganded ESR1 signaling reported in other cell types. Added estrogen further enhances ESR1 effects. We propose a hierarchical regulatory network for CYP3A4 expression directed by ESR1 through self-regulation, cross regulation, and TF-TF interactions. We also demonstrate that ESR1 regulates the expression of other P450 enzymes, suggesting broad influence of ESR1 on xenobiotics metabolism in human liver. Further studies are required to understand the mechanisms underlying role of ESR1 in P450 regulation. SIGNIFICANCE STATEMENT: This study focuses on identifying key transcription factors and regulatory networks for CYP3A4, the main drug metabolizing enzymes in liver. We applied a new computational approach (Sobol's sensitivity analysis) to existing hepatic gene expression data to determine the role of transcription factors in regulating CYP3A4 expression, and used molecular genetics methods (siRNA/shRNA gene knockdown and CRISPR-mediated transcriptional activation) to test these interactions in life cells. This approach reveals a robust network of TFs, including their putative interactions and the relative impact of each interaction. We find that ESR1 serves as a key transcription factor function in regulating CYP3A4, and it appears to be acting at least in part in a ligand-free fashion.
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Affiliation(s)
- Danxin Wang
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, College of Pharmacy, University of Florida, Gainesville, Florida (D.W.); Department of Clinical Sciences, Bioinformatics Core Facility, University of Texas Southwestern Medical Center, Dallas, Texas (R.L.); and Mathematical Bioscience Institute, (G.R.) and Center for Pharmacogenomics, Department of Cancer Biology and Genetics, College of Medicine (W.S.), Ohio State University, Columbus, Ohio
| | - Rong Lu
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, College of Pharmacy, University of Florida, Gainesville, Florida (D.W.); Department of Clinical Sciences, Bioinformatics Core Facility, University of Texas Southwestern Medical Center, Dallas, Texas (R.L.); and Mathematical Bioscience Institute, (G.R.) and Center for Pharmacogenomics, Department of Cancer Biology and Genetics, College of Medicine (W.S.), Ohio State University, Columbus, Ohio
| | - Grzegorz Rempala
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, College of Pharmacy, University of Florida, Gainesville, Florida (D.W.); Department of Clinical Sciences, Bioinformatics Core Facility, University of Texas Southwestern Medical Center, Dallas, Texas (R.L.); and Mathematical Bioscience Institute, (G.R.) and Center for Pharmacogenomics, Department of Cancer Biology and Genetics, College of Medicine (W.S.), Ohio State University, Columbus, Ohio
| | - Wolfgang Sadee
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, College of Pharmacy, University of Florida, Gainesville, Florida (D.W.); Department of Clinical Sciences, Bioinformatics Core Facility, University of Texas Southwestern Medical Center, Dallas, Texas (R.L.); and Mathematical Bioscience Institute, (G.R.) and Center for Pharmacogenomics, Department of Cancer Biology and Genetics, College of Medicine (W.S.), Ohio State University, Columbus, Ohio
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12
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Chaudhary S, Ganguly K, Muniyan S, Pothuraju R, Sayed Z, Jones DT, Batra SK, Macha MA. Immunometabolic Alterations by HPV Infection: New Dimensions to Head and Neck Cancer Disparity. J Natl Cancer Inst 2019; 111:233-244. [PMID: 30615137 PMCID: PMC6410958 DOI: 10.1093/jnci/djy207] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 09/29/2018] [Accepted: 11/05/2018] [Indexed: 12/12/2022] Open
Abstract
Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer, with high morbidity and mortality. Racial disparity in HNSCC is observed between African Americans (AAs) and whites, effecting both overall and 5-year survival, with worse prognosis for AAs. In addition to socio-economic status and demographic factors, many epidemiological studies have also identified factors including coexisting human papillomavirus (HPV) infection, primary tumor location, and a variety of somatic mutations that contribute to the prognostic incongruities in HNSCC patients among AAs and whites. Recent research also suggests HPV-induced dysregulation of tumor metabolism and immune microenvironment as the major regulators of HNSCC patient prognosis. Outcomes of several preclinical and clinical studies on targeted therapeutics warrant the need to elucidate the inherent mechanistic and population-based disparities underlying patient responses. This review systematically reports the underlying reasons for inconsistency in disease prognosis and therapy responses among HNSCC patients from different racial populations. The focus of this review is twofold: aside from discussing the causes of racial disparity, we also seek to identify the consequences of such disparity in terms of HPV infection and its associated mutational, metabolic, and immune landscapes. Considering the clinical impact of differential patient outcomes among AA and white populations, understanding the underlying cause of this disparity may pave the way for novel precision therapy for HNSCC.
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Affiliation(s)
- Sanjib Chaudhary
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
| | - Koelina Ganguly
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
| | - Sakthivel Muniyan
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
| | - Ramesh Pothuraju
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
| | - Zafar Sayed
- Department of Otolaryngology/Head and Neck Surgery, University of Nebraska Medical Center, Omaha, NE
| | - Dwight T Jones
- Department of Otolaryngology/Head and Neck Surgery, University of Nebraska Medical Center, Omaha, NE
| | - Surinder K Batra
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE
| | - Muzafar A Macha
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
- Department of Otolaryngology/Head and Neck Surgery, University of Nebraska Medical Center, Omaha, NE
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13
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Liakoni E, Edwards KC, St Helen G, Nardone N, Dempsey DA, Tyndale RF, Benowitz NL. Effects of Nicotine Metabolic Rate on Withdrawal Symptoms and Response to Cigarette Smoking After Abstinence. Clin Pharmacol Ther 2018; 105:641-651. [PMID: 30242831 DOI: 10.1002/cpt.1238] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 09/12/2018] [Indexed: 12/20/2022]
Abstract
This study investigated the influence of the rate of nicotine metabolism, as indicated by the nicotine metabolite ratio (NMR), on tobacco dependence. We stratified 136 smokers on the basis of saliva NMR as fast (n = 65) and slow (n = 71) metabolizers. Two "loading cigarettes" were smoked after overnight, and a "reward cigarette" was smoked after 6 hours of daytime, abstinence. Blood nicotine concentrations, expired carbon monoxide, withdrawal/craving, and reward questionnaires were collected before/after smoking and during daytime abstinence. Compared with slow metabolizers, fast metabolizers had a shorter nicotine elimination half-life (P < 0.001), lower plasma nicotine concentrations (P < 0.001), and higher withdrawal/craving scores (P < 0.05) for most times during daytime abstinence, indicating that fast metabolizers are likely smoking more to relieve withdrawal symptoms (negative reinforcement). Reward/satisfaction scores were similar in fast and slow metabolizers, suggesting that faster nicotine metabolism, assessed by NMR, is not associated with greater positive reinforcement. CYP2A6 normal (n = 82) and reduced (n = 42) genotype predicted plasma nicotine concentrations but not withdrawal symptoms.
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Affiliation(s)
- Evangelia Liakoni
- Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, San Francisco, California, USA.,Clinical Pharmacology and Toxicology, Department of General Internal Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Kathryn C Edwards
- Westat, Rockville, Maryland, USA.,Center for Tobacco Control Research and Education, University of California, San Francisco, San Francisco, California, USA
| | - Gideon St Helen
- Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, San Francisco, California, USA.,Center for Tobacco Control Research and Education, University of California, San Francisco, San Francisco, California, USA
| | - Natalie Nardone
- Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Delia A Dempsey
- Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Rachel F Tyndale
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Departments of Pharmacology and Toxicology and Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Neal L Benowitz
- Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, San Francisco, California, USA.,Center for Tobacco Control Research and Education, University of California, San Francisco, San Francisco, California, USA.,Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
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14
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Chenoweth MJ, Ware JJ, Zhu AZ, Cole CB, Sanderson Cox L, Nollen N, Ahluwalia JS, Benowitz NL, Schnoll RA, Hawk LW, Cinciripini PM, George TP, Lerman C, Knight J, Tyndale RF. Genome-wide association study of a nicotine metabolism biomarker in African American smokers: impact of chromosome 19 genetic influences. Addiction 2018; 113:509-523. [PMID: 28921760 PMCID: PMC5807179 DOI: 10.1111/add.14032] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/03/2017] [Accepted: 09/12/2017] [Indexed: 12/22/2022]
Abstract
BACKGROUND AND AIMS The activity of CYP2A6, the major nicotine-inactivating enzyme, is measurable in smokers using the nicotine metabolite ratio (NMR; 3'hydroxycotinine/cotinine). Due to its role in nicotine clearance, the NMR is associated with smoking behaviours and response to pharmacotherapies. The NMR is highly heritable (~80%), and on average lower in African Americans (AA) versus whites. We previously identified several reduce and loss-of-function CYP2A6 variants common in individuals of African descent. Our current aim was to identify novel genetic influences on the NMR in AA smokers using genome-wide approaches. DESIGN Genome-wide association study (GWAS). SETTING Multiple sites within Canada and the United States. PARTICIPANTS AA smokers from two clinical trials: Pharmacogenetics of Nicotine Addiction Treatment (PNAT)-2 (NCT01314001; n = 504) and Kick-it-at-Swope (KIS)-3 (NCT00666978; n = 450). MEASUREMENTS Genome-wide SNP genotyping, the NMR (phenotype) and population substructure and NMR covariates. FINDINGS Meta-analysis revealed three independent chromosome 19 signals (rs12459249, rs111645190 and rs185430475) associated with the NMR. The top overall hit, rs12459249 (P = 1.47e-39; beta = 0.59 per C (versus T) allele, SE = 0.045), located ~9.5 kb 3' of CYP2A6, remained genome-wide significant after controlling for the common (~10% in AA) non-functional CYP2A6*17 allele. In contrast, rs111645190 and rs185430475 were not genome-wide significant when controlling for CYP2A6*17. In total, 96 signals associated with the NMR were identified; many were not found in prior NMR GWASs in individuals of European descent. The top hits were also associated with the NMR in a third cohort of AA (KIS2; n = 480). None of the hits were in UGT or OCT2 genes. CONCLUSIONS Three independent chromosome 19 signals account for ~20% of the variability in the nicotine metabolite ratio in African American smokers. The hits identified may contribute to inter-ethnic variability in nicotine metabolism, smoking behaviours and tobacco-related disease risk.
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Affiliation(s)
- Meghan J. Chenoweth
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, M5T 1R8, Canada
| | - Jennifer J. Ware
- MRC Integrative Epidemiology Unit (IEU) and School of Social and Community Medicine at the University of Bristol, Bristol, BS8 2BN, United Kingdom
| | - Andy Z.X. Zhu
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, M5T 1R8, Canada
| | - Christopher B. Cole
- Data Science Institute and Lancaster University Medical School, Lancaster, LA1 4YW, United Kingdom
| | - Lisa Sanderson Cox
- Department of Preventive Medicine and Public Health, University of Kansas School of Medicine, Kansas City, Kansas, 66160, USA
| | - Nikki Nollen
- Department of Preventive Medicine and Public Health, University of Kansas School of Medicine, Kansas City, Kansas, 66160, USA
| | - Jasjit S. Ahluwalia
- Department of Behavioral and Social Sciences, Brown University School of Public Health, Providence, Rhode Island 02912, USA
| | - Neal L. Benowitz
- Departments of Medicine and Bioengineering and Therapeutic Sciences, Division of Clinical Pharmacology and Experimental Therapeutics, University of California, San Francisco, San Francisco, California, 94110, USA
| | - Robert A. Schnoll
- Department of Psychiatry, Perelman School of Medicine, and Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania, 19104-6376, USA
| | - Larry W. Hawk
- Department of Psychology, University at Buffalo, SUNY, Buffalo, New York, 14260-4110, USA
| | - Paul M. Cinciripini
- Department of Behavioral Science, University of Texas, MD Anderson Cancer Center, Houston, Texas, 77030, USA
| | - Tony P. George
- Division of Schizophrenia, Centre for Addiction and Mental Health, Toronto, Ontario, Canada and Division of Brain and Therapeutics, Department of Psychiatry, University of Toronto, Toronto, Ontario, M5T 1R8, Canada
| | - Caryn Lerman
- Department of Psychiatry, Annenberg School for Communication, and Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania, 19104-6376, USA
| | - Joanne Knight
- Data Science Institute and Lancaster University Medical School, Lancaster, LA1 4YW, United Kingdom
| | - Rachel F. Tyndale
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, M5T 1R8, Canada,Department of Psychiatry, University of Toronto, Toronto, Ontario, M5T 1R8, Canada,Corresponding author (RFT)
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15
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Tanner JA, Tyndale RF. Variation in CYP2A6 Activity and Personalized Medicine. J Pers Med 2017; 7:jpm7040018. [PMID: 29194389 PMCID: PMC5748630 DOI: 10.3390/jpm7040018] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 11/17/2017] [Accepted: 11/27/2017] [Indexed: 12/16/2022] Open
Abstract
The cytochrome P450 2A6 (CYP2A6) enzyme metabolizes several clinically relevant substrates, including nicotine-the primary psychoactive component in cigarette smoke. The gene that encodes the CYP2A6 enzyme is highly polymorphic, resulting in extensive interindividual variation in CYP2A6 enzyme activity and the rate of metabolism of nicotine and other CYP2A6 substrates including cotinine, tegafur, letrozole, efavirenz, valproic acid, pilocarpine, artemisinin, artesunate, SM-12502, caffeine, and tyrosol. CYP2A6 expression and activity are also impacted by non-genetic factors, including induction or inhibition by pharmacological, endogenous, and dietary substances, as well as age-related changes, or interactions with other hepatic enzymes, co-enzymes, and co-factors. As variation in CYP2A6 activity is associated with smoking behavior, smoking cessation, tobacco-related lung cancer risk, and with altered metabolism and resulting clinical responses for several therapeutics, CYP2A6 expression and enzyme activity is an important clinical consideration. This review will discuss sources of variation in CYP2A6 enzyme activity, with a focus on the impact of CYP2A6 genetic variation on metabolism of the CYP2A6 substrates.
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Affiliation(s)
- Julie-Anne Tanner
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, ON M5T 1R8, Canada.
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Rachel F Tyndale
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, ON M5T 1R8, Canada.
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada.
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Effect of UGT2B10, UGT2B17, FMO3, and OCT2 genetic variation on nicotine and cotinine pharmacokinetics and smoking in African Americans. Pharmacogenet Genomics 2017; 27:143-154. [PMID: 28178031 DOI: 10.1097/fpc.0000000000000269] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
OBJECTIVES Nicotine metabolism rates differ considerably among individuals, even after controlling for variation in the major nicotine-metabolizing enzyme, CYP2A6. In this study, the impact of genetic variation in alternative metabolic enzymes and transporters on nicotine and cotinine (COT) pharmacokinetics and smoking was investigated. METHODS We examined the impact of UGT2B10, UGT2B17, FMO3, NAT1, and OCT2 variation on pharmacokinetics and smoking (total nicotine equivalents and topography) before and after stratifying by CYP2A6 genotype in 60 African American (AA) smokers who received a simultaneous intravenous infusion of deuterium-labeled nicotine and COT. RESULTS Variants in UGT2B10 and UGT2B17 were associated with urinary glucuronidation ratios (glucuronide/free substrate). UGT2B10 rs116294140 was associated with significant alterations in COT and modest alterations in nicotine pharmacokinetics. These alterations, however, were not sufficient to change nicotine intake or topography. Neither UGT2B10 rs61750900, UGT2B17*2, FMO3 rs2266782, nor NAT1 rs13253389 altered nicotine or COT pharmacokinetics among all individuals (n=60) or among individuals with reduced CYP2A6 activity (n=23). The organic cation transporter OCT2 rs316019 significantly increased nicotine and COT Cmax (P=0.005, 0.02, respectively) and decreased nicotine clearance (P=0.05). UGT2B10 rs116294140 had no significant impact on the plasma or urinary trans-3'-hydroxycotinine/COT ratio, commonly used as a biomarker of CYP2A6 activity. CONCLUSION We found that polymorphisms in genes other than CYP2A6 represent minor sources of variation in nicotine pharmacokinetics, insufficient to alter smoking in AAs. The change in COT pharmacokinetics with UGT2B10 rs116294140 highlights the UGT2B10 gene as a source of variability in COT as a biomarker of tobacco exposure among AA smokers.
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17
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Disposition kinetics and metabolism of nicotine and cotinine in African American smokers: impact of CYP2A6 genetic variation and enzymatic activity. Pharmacogenet Genomics 2017; 26:340-50. [PMID: 27035242 DOI: 10.1097/fpc.0000000000000222] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
OBJECTIVE The rate of nicotine metabolism, determined primarily by CYP2A6 activity, influences tobacco dependence and smoking-induced disease risk. The prevalence of CYP2A6 gene variants differs by race, with greater numbers in African Americans compared with Caucasians. We studied nicotine disposition kinetics and metabolism by the CYP2A6 genotype and enzymatic activity, as measured by the nicotine metabolite ratio (NMR), in African American smokers. METHODS Participants were administered intravenous infusions of deuterium-labeled nicotine and cotinine. Plasma and urine concentrations of nicotine and metabolites were measured and pharmacokinetic parameters were estimated. RESULTS Pharmacokinetic parameters and urine metabolite excretion data were analyzed by CYP2A6 genotype and by NMR. A number of gene variants were associated with markedly reduced nicotine and cotinine clearances. NMR was strongly correlated with nicotine (r=0.72) and cotinine (r=0.80) clearances. Participants with higher NMR excreted significantly greater nicotine C-oxidation and lower non-C-oxidation products compared with lower NMR participants. CONCLUSION CYP2A6 genotype, NMR, and nicotine pharmacokinetic data may inform studies of individual differences in smoking behavior and biomarkers of nicotine exposure.
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18
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López-Flores LA, Pérez-Rubio G, Falfán-Valencia R. Distribution of polymorphic variants of CYP2A6 and their involvement in nicotine addiction. EXCLI JOURNAL 2017; 16:174-196. [PMID: 28507465 PMCID: PMC5427481 DOI: 10.17179/excli2016-847] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 02/13/2017] [Indexed: 01/08/2023]
Abstract
Tobacco consumption has become a major public health issue, which has motivated studies to identify and understand the biological processes involved in the smoking behavior for prevention and smoking cessation treatments. CYP2A6 has been identified as the main gene that codifies the enzyme that metabolizes nicotine. Many alleles have been identified after the discovery of CYP2A6, suggesting a wide interethnic variability and a diverse smoking behavior of the allele carrying individuals. The main purpose of this review is to update and highlight the effects of the CYP2A6 gene variability related to tobacco consumption reported from diverse human populations. The review further aims to consider CYP2A6 in future studies as a possible genetic marker for the prevention and treatment of nicotine addiction. Therefore, we analyzed several population studies and their importance at addressing and characterizing a population using specific parameters. Our efforts may contribute to a personalized system for detecting, preventing and treating populations at a higher risk of smoking to avoid diseases related to tobacco consumption.
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Hosono H, Kumondai M, Maekawa M, Yamaguchi H, Mano N, Oda A, Hirasawa N, Hiratsuka M. Functional Characterization of 34 CYP2A6 Allelic Variants by Assessment of Nicotine C-Oxidation and Coumarin 7-Hydroxylation Activities. Drug Metab Dispos 2016; 45:279-285. [PMID: 27974382 DOI: 10.1124/dmd.116.073494] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 12/13/2016] [Indexed: 11/22/2022] Open
Abstract
CYP2A6, a member of the cytochrome P450 (P450) family, is one of the enzymes responsible for the metabolism of therapeutic drugs and such tobacco components as nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and N-nitrosodiethylamine. Genetic polymorphisms in CYP2A6 are associated with individual variation in smoking behavior, drug toxicities, and the risk of developing several cancers. In this study, we conducted an in vitro analysis of 34 allelic variants of CYP2A6 using nicotine and coumarin as representative CYP2A6 substrates. These variant CYP2A6 proteins were heterologously expressed in 293FT cells, and their enzymatic activities were assessed on the basis of nicotine C-oxidation and coumarin 7-hydroxylation activities. Among the 34 CYP2A6 variants, CYP2A6.2, CYP2A6.5, CYP2A6.6, CYP2A6.10, CYP2A6.26, CYP2A6.36, and CYP2A6.37 exhibited no enzymatic activity, whereas 14 other variants exhibited markedly reduced activity toward both nicotine and coumarin. These comprehensive in vitro findings may provide useful insight into individual differences in smoking behavior, drug efficacy, and cancer susceptibility.
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Affiliation(s)
- Hiroki Hosono
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Masaki Kumondai
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Masamitsu Maekawa
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Hiroaki Yamaguchi
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Nariyasu Mano
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Akifumi Oda
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Noriyasu Hirasawa
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
| | - Masahiro Hiratsuka
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan (H.H., M.K., N.H., M.H.), Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai, Japan (M.M., H.Y., N.M.), Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan (A.O.)
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20
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Alexander LA, Trinidad DR, Sakuma KLK, Pokhrel P, Herzog TA, Clanton MS, Moolchan ET, Fagan P. Why We Must Continue to Investigate Menthol's Role in the African American Smoking Paradox. Nicotine Tob Res 2016; 18 Suppl 1:S91-101. [PMID: 26980870 DOI: 10.1093/ntr/ntv209] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND The disproportionate burden of tobacco use among African Americans is largely unexplained. The unexplained disparities, referred to as the African American smoking paradox, includes several phenomena. Despite their social disadvantage, African American youth have lower smoking prevalence rates, initiate smoking at older ages, and during adulthood, smoking rates are comparable to whites. Smoking frequency and intensity among African American youth and adults are lower compared to whites and American Indian and Alaska Natives, but tobacco-caused morbidity and mortality rates are disproportionately higher. Disease prediction models have not explained disease causal pathways in African Americans. It has been hypothesized that menthol cigarette smoking, which is disproportionately high among African Americans, may help to explain several components of the African American smoking paradox. PURPOSE This article provides an overview of the potential role that menthol plays in the African American smoking paradox. We also discuss the research needed to better understand this unresolved puzzle. METHODS We examined prior synthesis reports and reviewed the literature in PubMed on the menthol compound and menthol cigarette smoking in African Americans. RESULTS The pharmacological and physiological effects of menthol and their interaction with biological and genetic factors may indirectly contribute to the disproportionate burden of cigarette use and diseases among African Americans. CONCLUSIONS Future studies that examine taste sensitivity, the menthol compound, and their effects on smoking and chronic disease would provide valuable information on how to reduce the tobacco burden among African Americans. IMPLICATIONS Our study highlights four counterintuitive observations related to the smoking risk profiles and chronic disease outcomes among African Americans. The extant literature provides strong evidence of their existence and shows that long-standing paradoxes have been largely unaffected by changes in the social environment. African Americans smoke menthols disproportionately, and menthol's role in the African American smoking paradox has not been thoroughly explored. We propose discrete hypotheses that will help to explain the phenomena and encourage researchers to empirically test menthol's role in smoking initiation, transitions to regular smoking and chronic disease outcomes in African Americans.
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Affiliation(s)
- Linda A Alexander
- College of Public Health, University of Kentucky College of Public Health, Lexington, KY
| | - Dennis R Trinidad
- Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, CA
| | - Kari-Lyn K Sakuma
- College of Public Health and Human Sciences, Oregon State University, Corvallis, OR
| | - Pallav Pokhrel
- University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI
| | - Thaddeus A Herzog
- University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI
| | | | | | - Pebbles Fagan
- University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI;
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21
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Nollen NL, Cox LS, Yu Q, Ellerbeck EF, Scheuermann TS, Benowitz NL, Tyndale RF, Mayo MS, Ahluwalia JS. A clinical trial to examine disparities in quitting between African-American and White adult smokers: Design, accrual, and baseline characteristics. Contemp Clin Trials 2016; 47:12-21. [PMID: 26667382 PMCID: PMC4818177 DOI: 10.1016/j.cct.2015.12.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/24/2015] [Accepted: 12/03/2015] [Indexed: 01/21/2023]
Abstract
BACKGROUND African-Americans smoke fewer cigarettes per day than Whites but experience greater smoking attributable morbidity and mortality. African-American-White differences may also exist in cessation but rigorously designed studies have not been conducted to empirically answer this question. METHODS/DESIGN Quit2Live is, to our knowledge, the first head-to-head trial designed with the primary aim of examining African-American-White disparities in quitting smoking. Secondary aims are to identify mechanisms that mediate and/or moderate the relationship between race and quitting. The study is ongoing. Study aims are accomplished through a 5-year prospective cohort intervention study designed to recruit equal numbers of African-Americans (n=224) and Whites (n=224) stratified on age (<40, ≥40) and gender, key factors known to impact cessation, and all within a restricted income range (≤400% federal poverty level). All participants will receive 12 weeks of varenicline in combination with smoking cessation counseling. The primary outcome is cotinine-verified 7-day point prevalence abstinence from smoking at week 26. Secondary outcomes are cotinine-verified 7-day point prevalence abstinence from smoking at weeks 4 and 12. DISCUSSION Findings from Quit2Live will not only address if African-American-White disparities in quitting smoking exist but, more importantly, will examine mechanisms underlying the difference. Attention to proximal, modifiable mechanisms (e.g., adherence, response to treatment, depression, stress) maximizes Quit2Live's potential to inform practice. Findings will provide an empirically-derived approach that will guide researchers and clinicians in identifying specific factors to address to improve cessation outcomes and reduce tobacco-related morbidity and mortality in African-American and White smokers. TRIAL REGISTRATION NUMBER ClinicalTrials.gov: NCT01836276.
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Affiliation(s)
- Nicole L Nollen
- Department of Preventive Medicine and Public Health, University of Kansas School of Medicine, Kansas City, Kansas, United States.
| | - Lisa Sanderson Cox
- Department of Preventive Medicine and Public Health, University of Kansas School of Medicine, Kansas City, Kansas, United States.
| | - Qing Yu
- Department of Biostatistics, University of Kansas School of Medicine, Kansas City, Kansas, United States.
| | - Edward F Ellerbeck
- Department of Preventive Medicine and Public Health, University of Kansas School of Medicine, Kansas City, Kansas, United States.
| | - Taneisha S Scheuermann
- Department of Preventive Medicine and Public Health, University of Kansas School of Medicine, Kansas City, Kansas, United States.
| | - Neal L Benowitz
- Division of Clinical Pharmacology and Experimental Therapeutics, University of California, San Francisco, San Francisco, California, United States; Department of Medicine, University of California, San Francisco, San Francisco, California, United States; Department of Bioengineering, University of California, San Francisco, San Francisco, California, United States; Department of Therapeutic Sciences, University of California, San Francisco, San Francisco, California, United States.
| | - Rachel F Tyndale
- Center for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada.
| | - Matthew S Mayo
- Department of Biostatistics, University of Kansas School of Medicine, Kansas City, Kansas, United States.
| | - Jasjit S Ahluwalia
- Department of Epidemiology, Rutgers School of Public Health, Piscataway, New Jersey, United States.
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22
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Park SL, Tiirikainen MI, Patel YM, Wilkens LR, Stram DO, Le Marchand L, Murphy SE. Genetic determinants of CYP2A6 activity across racial/ethnic groups with different risks of lung cancer and effect on their smoking intensity. Carcinogenesis 2016; 37:269-279. [PMID: 26818358 DOI: 10.1093/carcin/bgw012] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 01/19/2016] [Indexed: 01/22/2023] Open
Abstract
Genetic variation in cytochrome P450 2A6 (CYP2A6) gene is the primary contributor to the intraindividual and interindividual differences in nicotine metabolism and has been found to influence smoking intensity. However, no study has evaluated the relationship between CYP2A6 genetic variants and the CYP2A6 activity ratio (total 3-hydroxycotinine/cotinine) and their influence on smoking intensity [total nicotine equivalents (TNE)], across five racial/ethnic groups found to have disparate rates of lung cancer. This study genotyped 10 known functional CYP2A6 genetic or copy number variants in 2115 current smokers from the multiethnic cohort study [African Americans (AA) = 350, Native Hawaiians (NH) = 288, Whites = 413, Latinos (LA) = 437 and Japanese Americans (JA) = 627] to conduct such an investigation. Here, we found that LA had the highest CYP2A6 activity followed by Whites, AA, NH and JA, who had the lowest levels. Adjusting for age, sex, race/ethnicity and body mass index, we found that CYP2A6 diplotypes were predictive of TNE levels, particularly in AA and JA (P trend < 0.0001). However, only in JA did the association remain after accounting for cigarettes per day. Also, it is only in this population that the lower activity ratio supports lower TNE levels, carcinogen exposure and thereby lower risk of lung cancer. Despite the association between nicotine metabolism (CYP2A6 activity phenotype and diplotypes) and smoking intensity (TNE), CYP2A6 levels did not correlate with the higher TNE levels found in AA nor the lower TNE levels found in LA, suggesting that other factors may influence smoking dose in these populations. Therefore, further study in these populations is recommended.
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Affiliation(s)
| | - Maarit I Tiirikainen
- Epidemiology Program, University of Hawaii Cancer Center , Honolulu, HI 96813 , USA and
| | | | - Lynne R Wilkens
- Epidemiology Program, University of Hawaii Cancer Center , Honolulu, HI 96813 , USA and
| | | | - Loic Le Marchand
- Epidemiology Program, University of Hawaii Cancer Center , Honolulu, HI 96813 , USA and
| | - Sharon E Murphy
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota , 2231 6th Street SE, 2-127 CCRB, Minneapolis, MN 55455 , USA
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23
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Ramakodi MP, Kulathinal RJ, Chung Y, Serebriiskii I, Liu JC, Ragin CC. Ancestral-derived effects on the mutational landscape of laryngeal cancer. Genomics 2015; 107:76-82. [PMID: 26721311 DOI: 10.1016/j.ygeno.2015.12.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 11/26/2015] [Accepted: 12/21/2015] [Indexed: 10/22/2022]
Abstract
Laryngeal cancer disproportionately affects more African-Americans than European-Americans. Here, we analyze the genome-wide somatic point mutations from the tumors of 13 African-Americans and 57 European-Americans from TCGA to differentiate between environmental and ancestrally-inherited factors. The mean number of mutations was different between African-Americans (151.31) and European-Americans (277.63). Other differences in the overall mutational landscape between African-American and European-American were also found. The frequency of C>A, and C>G were significantly different between the two populations (p-value<0.05). Context nucleotide signatures for some mutation types significantly differ between these two populations. Thus, the context nucleotide signatures along with other factors could be related to the observed mutational landscape differences between two races. Finally, we show that mutated genes associated with these mutational differences differ between the two populations. Thus, at the molecular level, race appears to be a factor in the progression of laryngeal cancer with ancestral genomic signatures best explaining these differences.
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Affiliation(s)
- Meganathan P Ramakodi
- Cancer Prevention and Control Program, Fox Chase Cancer Center-Temple Health, Philadelphia, PA 19111, USA; Department of Biology, Temple University, Philadelphia, PA 19122, USA; African-Caribbean Cancer Consortium; Center for Computational Genetics and Genomics, Temple University, Philadelphia, PA 19122, USA
| | - Rob J Kulathinal
- Department of Biology, Temple University, Philadelphia, PA 19122, USA; African-Caribbean Cancer Consortium; Center for Computational Genetics and Genomics, Temple University, Philadelphia, PA 19122, USA
| | - Yujin Chung
- Department of Biology, Temple University, Philadelphia, PA 19122, USA; Center for Computational Genetics and Genomics, Temple University, Philadelphia, PA 19122, USA
| | - Ilya Serebriiskii
- Developmental Therapeutics, Fox Chase Cancer Center- Temple Health, Philadelphia, PA 19111, USA; Kazan Federal University, Kazan, Russia
| | - Jeffrey C Liu
- Cancer Prevention and Control Program, Fox Chase Cancer Center-Temple Health, Philadelphia, PA 19111, USA; Department of Otolaryngology - Head and Neck Surgery, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Camille C Ragin
- Cancer Prevention and Control Program, Fox Chase Cancer Center-Temple Health, Philadelphia, PA 19111, USA; African-Caribbean Cancer Consortium; Department of Otolaryngology - Head and Neck Surgery, Temple University School of Medicine, Philadelphia, PA 19140, USA; College of Public Health, Temple University, Philadelphia, PA 19122, USA.
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24
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Wassenaar CA, Zhou Q, Tyndale RF. CYP2A6 genotyping methods and strategies using real-time and end point PCR platforms. Pharmacogenomics 2015; 17:147-62. [PMID: 26670214 DOI: 10.2217/pgs.15.156] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
CYP2A6 genotyping is of clinical importance--CYP2A6 gene variants influence nicotine metabolism and are associated with nicotine dependence, cigarettes per day, smoking cessation and the risk for tobacco-associated cancers. CYP2A6 gene variants also influence the metabolism of therapeutic drugs, such as the anticancer agents, tegafur and letrozole. Over the years, CYP2A6 genotyping methods have evolved to incorporate novel gene variants and to circumvent genotyping errors resulting from the high degree of homology between CYP2A6 and neighboring CYP2A genes. Herein, CYP2A6 genotyping strategies are described for commonly genotyped functionally significant alleles including SNPs, small insertions/deletions and more complex structural variants. The methods presented utilize higher throughput SYBR green real-time PCR technology in addition to standard thermocycling.
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Affiliation(s)
- Catherine A Wassenaar
- Department of Pharmacology & Toxicology, University of Toronto, 1 King's College Circle, Toronto, M5S 1A8 ON, Canada
| | - Qian Zhou
- Department of Pharmacology & Toxicology, University of Toronto, 1 King's College Circle, Toronto, M5S 1A8 ON, Canada
| | - Rachel F Tyndale
- Campbell Family Mental Health Research Institute, Centre for Addiction & Mental Health (CAMH), Departments of Pharmacology & Toxicology & Psychiatry, University of Toronto, 1 King's College Circle, Toronto, M5S 1A8 ON, Canada
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25
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Uno T, Ogura C, Izumi C, Nakamura M, Yanase T, Yamazaki H, Ashida H, Kanamaru K, Yamagata H, Imaishi H. Point mutation of cytochrome P450 2A6 (a polymorphic variant CYP2A6.25) confers new substrate specificity towards flavonoids. Biopharm Drug Dispos 2015. [DOI: 10.1002/bdd.1966] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tomohide Uno
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Chika Ogura
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Chiho Izumi
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Masahiko Nakamura
- Department of Bioscience and Biotechnology, Faculty of Bioenvironmental Science; Kyoto Gakuen University; 1-1 Nanjo, Sogabe Kameoka Kyoto 621-8555 Japan
| | - Takeshi Yanase
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Hiroshi Yamazaki
- Laboratory of Drug Metabolism and Pharmacokinetics; Showa Pharmaceutical University; Machida Tokyo 194-8543 Japan
| | - Hitoshi Ashida
- Laboratory of Biochemistry Frontiers, Graduate School of Agricultural Science; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Kengo Kanamaru
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Hiroshi Yamagata
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
| | - Hiromasa Imaishi
- Functional Analysis of Environmental Genes, Research Center for Environmental Genomics; Kobe University; Nada-ku Kobe Hyogo 657-8501 Japan
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26
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Bergen AW, Michel M, Nishita D, Krasnow R, Javitz HS, Conneely KN, Lessov-Schlaggar CN, Hops H, Zhu AZX, Baurley JW, McClure JB, Hall SM, Baker TB, Conti DV, Benowitz NL, Lerman C, Tyndale RF, Swan GE. Drug Metabolizing Enzyme and Transporter Gene Variation, Nicotine Metabolism, Prospective Abstinence, and Cigarette Consumption. PLoS One 2015; 10:e0126113. [PMID: 26132489 PMCID: PMC4488893 DOI: 10.1371/journal.pone.0126113] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Accepted: 03/29/2015] [Indexed: 11/28/2022] Open
Abstract
The Nicotine Metabolite Ratio (NMR, ratio of trans-3’-hydroxycotinine and cotinine), has previously been associated with CYP2A6 activity, response to smoking cessation treatments, and cigarette consumption. We searched for drug metabolizing enzyme and transporter (DMET) gene variation associated with the NMR and prospective abstinence in 2,946 participants of laboratory studies of nicotine metabolism and of clinical trials of smoking cessation therapies. Stage I was a meta-analysis of the association of 507 common single nucleotide polymorphisms (SNPs) at 173 DMET genes with the NMR in 449 participants of two laboratory studies. Nominally significant associations were identified in ten genes after adjustment for intragenic SNPs; CYP2A6 and two CYP2A6 SNPs attained experiment-wide significance adjusted for correlated SNPs (CYP2A6 PACT=4.1E-7, rs4803381 PACT=4.5E-5, rs1137115, PACT=1.2E-3). Stage II was mega-regression analyses of 10 DMET SNPs with pretreatment NMR and prospective abstinence in up to 2,497 participants from eight trials. rs4803381 and rs1137115 SNPs were associated with pretreatment NMR at genome-wide significance. In post-hoc analyses of CYP2A6 SNPs, we observed nominally significant association with: abstinence in one pharmacotherapy arm; cigarette consumption among all trial participants; and lung cancer in four case:control studies. CYP2A6 minor alleles were associated with reduced NMR, CPD, and lung cancer risk. We confirmed the major role that CYP2A6 plays in nicotine metabolism, and made novel findings with respect to genome-wide significance and associations with CPD, abstinence and lung cancer risk. Additional multivariate analyses with patient variables and genetic modeling will improve prediction of nicotine metabolism, disease risk and smoking cessation treatment prognosis.
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Affiliation(s)
- Andrew W. Bergen
- Center for Health Sciences, SRI International, Menlo Park, California, United States of America
- * E-mail:
| | - Martha Michel
- Academic Research Systems, University of California San Francisco, San Francisco, California, United States of America
| | - Denise Nishita
- Center for Health Sciences, SRI International, Menlo Park, California, United States of America
| | - Ruth Krasnow
- Center for Health Sciences, SRI International, Menlo Park, California, United States of America
| | - Harold S. Javitz
- Center for Health Sciences, SRI International, Menlo Park, California, United States of America
| | - Karen N. Conneely
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | | | - Hyman Hops
- Oregon Research Institute, Eugene, Oregon, United States of America
| | - Andy Z. X. Zhu
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | | | - Jennifer B. McClure
- Group Health Research Institute, Seattle, Washington, United States of America
| | - Sharon M. Hall
- Department of Psychiatry, University of California San Francisco, San Francisco, California, United States of America
| | - Timothy B. Baker
- Center for Tobacco Research and Intervention, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - David V. Conti
- Department of Preventive Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Neal L. Benowitz
- Departments of Medicine and of Bioengineering & Therapeutic Sciences, University of California San Francisco, San Francisco, California, United States of America
| | - Caryn Lerman
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Rachel F. Tyndale
- Cambell Family Mental Health Research Institute, Centre for Addiction and Mental Health, and Departments of Psychiatry, and of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - Gary E. Swan
- Oregon Research Institute, Eugene, Oregon, United States of America
- Stanford Prevention Research Center, Department of Medicine, Stanford University School of Medicine, Palo Alto, California, United States of America
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27
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Fagan P, Pokhrel P, Herzog TA, Pagano IS, Franke AA, Clanton MS, Alexander LA, Trinidad DR, Sakuma KLK, Johnson CA, Moolchan ET. Nicotine Metabolism in Young Adult Daily Menthol and Nonmenthol Smokers. Nicotine Tob Res 2015; 18:437-46. [PMID: 25995160 DOI: 10.1093/ntr/ntv109] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 05/12/2015] [Indexed: 12/22/2022]
Abstract
INTRODUCTION Menthol cigarette smoking may increase the risk for tobacco smoke exposure and inhibit nicotine metabolism in the liver. Nicotine metabolism is primarily mediated by the enzyme CYP2A6 and the nicotine metabolite ratio (NMR = trans 3' hydroxycotinine/cotinine) is a phenotypic proxy for CYP2A6 activity. No studies have examined differences in this biomarker among young adult daily menthol and nonmenthol smokers. This study compares biomarkers of tobacco smoke exposure among young adult daily menthol and nonmenthol smokers. METHODS Saliva cotinine and carbon monoxide were measured in a multiethnic sample of daily smokers aged 18-35 (n = 186). Nicotine, cotinine, the cotinine/cigarette per day ratio, trans 3' hydroxycotinine, the NMR, and expired carbon monoxide were compared. RESULTS The geometric means for nicotine, cotinine, and the cotinine/cigarette per day ratio did not significantly differ between menthol and nonmenthol smokers. The NMR was significantly lower among menthol compared with nonmenthol smokers after adjusting for race/ethnicity, gender, body mass index, and cigarette smoked per day (0.19 vs. 0.24, P = .03). White menthol smokers had significantly higher cotinine/cigarettes per day ratio than white nonmenthol smokers in the adjusted model. White menthol smokers had a lower NMR in the unadjusted model (0.24 vs. 0.31, P = .05) and the differences remained marginally significant in the adjusted model (0.28 vs. 0.34, P = .06). We did not observe these differences in Native Hawaiians and Filipinos. CONCLUSIONS Young adult daily menthol smokers have slower rates of nicotine metabolism than nonmenthol smokers. Studies are needed to determine the utility of this biomarker for smoking cessation treatment assignments.
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Affiliation(s)
- Pebbles Fagan
- Cancer Prevention and Control Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI;
| | - Pallav Pokhrel
- Cancer Prevention and Control Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI
| | - Thaddeus A Herzog
- Cancer Prevention and Control Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI
| | - Ian S Pagano
- Cancer Prevention and Control Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI
| | - Adrian A Franke
- Cancer Prevention and Control Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI
| | | | | | - Dennis R Trinidad
- School of Community and Global Health, Claremont Graduate University, Claremont, CA
| | - Kari-Lyn K Sakuma
- College of Public Health and Human Sciences, Oregon State University, Corvallis, OR
| | - Carl A Johnson
- School of Community and Global Health, Claremont Graduate University, Claremont, CA
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28
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Fagan P, Moolchan ET, Pokhrel P, Herzog T, Cassel KD, Pagano I, Franke AA, Kaholokula JK, Sy A, Alexander LA, Trinidad DR, Sakuma KL, Johnson CA, Antonio A, Jorgensen D, Lynch T, Kawamoto C, Clanton MS. Biomarkers of tobacco smoke exposure in racial/ethnic groups at high risk for lung cancer. Am J Public Health 2015; 105:1237-45. [PMID: 25880962 DOI: 10.2105/ajph.2014.302492] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
OBJECTIVES We examined biomarkers of tobacco smoke exposure among Native Hawaiians, Filipinos, and Whites, groups that have different lung cancer risk. METHODS We collected survey data and height, weight, saliva, and carbon monoxide (CO) levels from a sample of daily smokers aged 18-35 (n = 179). Mean measures of nicotine, cotinine, cotinine/cigarettes per day ratio, trans 3' hydroxycotinine, the nicotine metabolite ratio (NMR), and expired CO were compared among racial/ethnic groups. RESULTS The geometric means for cotinine, the cotinine/cigarettes per day ratio, and CO did not significantly differ among racial/ethnic groups in the adjusted models. After adjusting for gender, body mass index, menthol smoking, Hispanic ethnicity, and number of cigarettes smoked per day, the NMR was significantly higher among Whites than among Native Hawaiians and Filipinos (NMR = 0.33, 0.20, 0.19, P ≤ .001). The NMR increased with increasing White parental ancestry. The NMR was not significantly correlated with social-environmental stressors. CONCLUSIONS Racial/ethnic groups with higher rates of lung cancer had slower nicotine metabolism than Whites. The complex relationship between lung cancer risk and nicotine metabolism among racial/ethnic groups needs further clarification.
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Affiliation(s)
- Pebbles Fagan
- Pebbles Fagan, Pallav Pokhrel, Thaddeus Herzog, Kevin D. Cassel, Ian Pagano, Adrian A. Franke, Alyssa Antonio, Dorothy Jorgensen, Tania Lynch, and Crissy Kawamoto are with the University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu. Eric T. Moolchan is an independent consultant, Cambridge, MA. Joseph Keawe'aimoku Kaholokula is with the John A. Burns School of Medicine, University of Hawaii at Manoa. Angela Sy is with the School of Nursing and Dental Hygiene, University of Hawaii at Manoa. Linda A. Alexander is with the University of Kentucky College of Public Health, Lexington. Dennis R. Trinidad and C. Anderson Johnson are with the School of Community and Global Health, Claremont Graduate University, CA. Kari-Lyn Sakuma is with the College of Public Health and Human Sciences, Oregon State University, Corvallis. Mark S. Clanton is with the TMF Health Quality Institute, Austin, TX
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Tanner JA, Chenoweth MJ, Tyndale RF. Pharmacogenetics of nicotine and associated smoking behaviors. Curr Top Behav Neurosci 2015; 23:37-86. [PMID: 25655887 DOI: 10.1007/978-3-319-13665-3_3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This chapter summarizes genetic factors that contribute to variation in nicotine pharmacokinetics and nicotine's pharmacological action in the central nervous system (CNS), and how this in turn influences smoking behaviors. Nicotine, the major psychoactive compound in cigarette smoke, is metabolized by a number of enzymes, including CYP2A6, CYP2B6, FMOs, and UGTs, among others. Variation in the genes encoding these enzymes, in particular CYP2A6, can alter the rate of nicotine metabolism and smoking behaviors. Faster nicotine metabolism is associated with higher cigarette consumption and nicotine dependence, as well as lower quit rates. Variation in nicotine's CNS targets and downstream signaling pathways can also contribute to interindividual differences in smoking patterns. Binding of nicotine to neuronal nicotinic acetylcholine receptors (nAChRs) mediates the release of several neurotransmitters including dopamine and serotonin. Genetic variation in nAChRs, and in transporter and enzyme systems that leads to altered CNS levels of dopamine and serotonin, is associated with a number of smoking behaviors. To date, the precise mechanism underpinning many of these findings remains unknown. Considering the complex etiology of nicotine addiction, a more comprehensive approach that assesses the contribution of multiple gene variants, and their interaction with environmental factors, will likely improve personalized therapeutic approaches and increase smoking cessation rates.
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Affiliation(s)
- Julie-Anne Tanner
- Departments of Pharmacology and Toxicology and Psychiatry, University of Toronto, Toronto, ON, Canada
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Wassenaar CA, Ye Y, Cai Q, Aldrich MC, Knight J, Spitz MR, Wu X, Blot WJ, Tyndale RF. CYP2A6 reduced activity gene variants confer reduction in lung cancer risk in African American smokers--findings from two independent populations. Carcinogenesis 2014; 36:99-103. [PMID: 25416559 DOI: 10.1093/carcin/bgu235] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We investigated genetic variation in CYP2A6 in relation to lung cancer risk among African American smokers, a high-risk population. Previously, we found that CYP2A6, a nicotine/nitrosamine metabolism gene, was associated with lung cancer risk in European Americans, but smoking habits, lung cancer risk and CYP2A6 gene variants differ significantly between European and African ancestry populations. Herein, African American ever-smokers, drawn from two independent lung cancer case-control studies, were genotyped for reduced activity CYP2A6 alleles and grouped by predicted metabolic activity. Lung cancer risk in the Southern Community Cohort Study (n = 494) was lower among CYP2A6 reduced versus normal metabolizers, as estimated by multivariate conditional logistic regression [odds ratio (OR) = 0.44; 95% confidence interval (CI) = 0.26-0.73] and by unconditional logistic regression (OR = 0.62; 95% CI = 0.41-0.94). The association was replicated in an independent study from MD Anderson Cancer Center (n = 407) (OR = 0.64; 95% CI = 0.42-0.98), and pooling the studies yielded an OR of 0.64 (95% CI = 0.48-0.86). Exploratory analyses revealed a significant interaction between CYP2A6 genotype and sex on the risk for lung cancer (Southern Community Cohort Study: P = 0.04; MD Anderson: P = 0.03; Pooled studies: P = 0.002) with a CYP2A6 effect in men only. These findings support a contribution of genetic variation in CYP2A6 to lung cancer risk among African American smokers, particularly men, whereby CYP2A6 genotypes associated with reduced metabolic activity confer a lower risk of developing lung cancer.
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Affiliation(s)
- Catherine A Wassenaar
- Department of Pharmacology and Toxicology, The University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Yuanqing Ye
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Qiuyin Cai
- Division of Epidemiology, Vanderbilt University School of Medicine, Nashville, TN 37203, USA
| | - Melinda C Aldrich
- Division of Epidemiology, Vanderbilt University School of Medicine, Nashville, TN 37203, USA, Department of Thoracic Surgery Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Joanne Knight
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario M5T 1R8, Canada, Department of Psychiatry, The University of Toronto, Toronto, Ontario M5T 1R8, Canada
| | - Margaret R Spitz
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA and
| | - Xifeng Wu
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - William J Blot
- Division of Epidemiology, Vanderbilt University School of Medicine, Nashville, TN 37203, USA, International Epidemiology Institute, Rockville, MD 20850, USA
| | - Rachel F Tyndale
- Department of Pharmacology and Toxicology, The University of Toronto, Toronto, Ontario M5S 1A8, Canada, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario M5T 1R8, Canada, Department of Psychiatry, The University of Toronto, Toronto, Ontario M5T 1R8, Canada,
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Variation in P450 oxidoreductase (POR) A503V and flavin-containing monooxygenase (FMO)-3 E158K is associated with minor alterations in nicotine metabolism, but does not alter cigarette consumption. Pharmacogenet Genomics 2014; 24:172-6. [PMID: 24448396 DOI: 10.1097/fpc.0000000000000031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The rates of nicotine metabolism differ widely, even after controlling for genetic variation in the major nicotine-metabolizing enzyme, CYP2A6. Genetic variants in an additional nicotine-metabolizing enzyme, flavin-containing monooxygenase (FMO)-3, and an obligate microsomal CYP-supportive enzyme, cytochrome P450 oxidoreductase (POR), were investigated. We examined the impact of FMO3 E158K and POR A503V before and after stratifying by CYP2A6 metabolism group. In 130 nonsmokers of African descent who received 4 mg oral nicotine, FMO3 158K trended toward slower nicotine metabolism in reduced CYP2A6 metabolizers (P=0.07) only, whereas POR 503V was associated with faster CYP2A6 activity (nicotine metabolite ratio) in normal (P=0.03), but not reduced, CYP2A6 metabolizers. Neither FMO3 158K nor POR 503V significantly altered the nicotine metabolic ratio (N=659), cigarette consumption (N=667), or urine total nicotine equivalents (N=418) in smokers of African descent. Thus, FMO3 E158K and POR A503V are minor sources of nicotine metabolism variation, insufficient to appreciably alter smoking.
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Novel CYP2A6 variants identified in African Americans are associated with slow nicotine metabolism in vitro and in vivo. Pharmacogenet Genomics 2014; 24:118-28. [PMID: 24305170 DOI: 10.1097/fpc.0000000000000026] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Nicotine, the main addictive ingredient in tobacco, is metabolically inactivated to cotinine primarily by the hepatic enzyme CYP2A6. Considerable genetic variation in the CYP2A6 gene results in large variation in the rates of nicotine metabolism, which in turn alters smoking behaviours (e.g. amount of cigarettes smoked, risk for dependence and success in smoking cessation). The aim of this study was to identify and characterize novel variants in CYP2A6. MATERIALS AND METHODS The CYP2A6 gene from African American phenotypically slow nicotine metabolizers was sequenced and seven novel variants were identified [CYP2A6*39 (V68M), CYP2A6*40 (I149M), CYP2A6*41 (R265Q), CYP2A6*42 (I268T), CYP2A6*43 (T303I), CYP2A6*44 (E390K), CYP2A6*44 (L462P)]. Variants were introduced into a bi-cistronic cDNA expression construct containing CYP2A6 and P450 oxidoreductase and assessed for protein expression, enzymatic activity and stability as evaluated using western blotting and nicotine metabolism. Genotyping assays were developed and allelic frequencies were assessed in 534 African Americans. RESULTS The variants showed significantly lower protein expression (P<0.001) when compared with the wild-type as well as reduced metabolism of nicotine to cotinine when controlling for cDNA expression using P450 oxidoreductase (P<0.001). The variants also showed reduced stability at 37°C. Allelic frequencies ranged from 0.1 to 0.6% with a collective genotype frequency of 3.2%; the impact in vitro correlated significantly with in-vivo activity (R(2)=0.40-0.48, P<0.05). Together, those with a novel variant had significantly lower nicotine metabolism in vivo than those without genetic variants (P<0.01). CONCLUSION Here, we identified a number of novel variants with reduced/loss of CYP2A6 activity, increasing our understanding of CYP2A6 genetic variability.
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Saladores PH, Precht JC, Schroth W, Brauch H, Schwab M. Impact of metabolizing enzymes on drug response of endocrine therapy in breast cancer. Expert Rev Mol Diagn 2013; 13:349-65. [PMID: 23638818 DOI: 10.1586/erm.13.26] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Estrogen-receptor positive breast cancer accounts for 75% of diagnosed breast cancers worldwide. There are currently two major options for adjuvant treatment: tamoxifen and aromatase inhibitors. Variability in metabolizing enzymes determines their pharmacokinetic profile, possibly affecting treatment response. Therefore, prediction of therapy outcome based on genotypes would enable a more personalized medicine approach, providing optimal therapy for each patient. In this review, the authors will discuss the current evidence on the most important metabolizing enzymes in endocrine therapy, with a special focus on CYP2D6 and its role in tamoxifen metabolism.
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Affiliation(s)
- Pilar H Saladores
- Dr Margarete Fischer-Bosch-Institute of Clinical Pharmacology and University of Tübingen, Auerbachstr. 112, 70376 Stuttgart, Germany
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Martiny VY, Miteva MA. Advances in molecular modeling of human cytochrome P450 polymorphism. J Mol Biol 2013; 425:3978-92. [PMID: 23856621 DOI: 10.1016/j.jmb.2013.07.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 07/01/2013] [Accepted: 07/02/2013] [Indexed: 01/08/2023]
Abstract
Cytochrome P450 (CYP) is a supergene family of metabolizing enzymes involved in the phase I metabolism of drugs and endogenous compounds. CYP oxidation often leads to inactive drug metabolites or to highly toxic or carcinogenic metabolites involved in adverse drug reactions (ADR). During the last decade, the impact of CYP polymorphism in various drug responses and ADR has been demonstrated. Of the drugs involved in ADR, 56% are metabolized by polymorphic phase I metabolizing enzymes, 86% among them being CYP. Here, we review the major CYP polymorphic forms, their impact for drug response and current advances in molecular modeling of CYP polymorphism. We focus on recent studies exploring CYP polymorphism performed by the use of sequence-based and/or protein-structure-based computational approaches. The importance of understanding the molecular mechanisms related to CYP polymorphism and drug response at the atomic level is outlined.
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Affiliation(s)
- Virginie Y Martiny
- Université Paris Diderot, Sorbonne Paris Cité, Molécules Thérapeutiques In Silico, Inserm UMR-S 973, 35 rue Helene Brion, 75013 Paris, France; Inserm, U973, F-75205 Paris, France
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35
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A compensatory effect upon splicing results in normal function of the CYP2A6*14 allele. Pharmacogenet Genomics 2013; 23:107-16. [PMID: 23292114 DOI: 10.1097/fpc.0b013e32835caf7d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A synonymous variant in the first exon of CYP2A6, rs1137115 (51G>A), defines the common reference allele CYP2A6*1A, and is associated with lower mRNA expression and slower in-vivo nicotine metabolism. Another common allele, CYP2A6*14, differs from CYP2A6*1A by a single variant, rs28399435 (86G>A, S29N). However, CYP2A6*14 shows in-vivo activity comparable with that of full-function alleles, and significantly higher than CYP2A6*1A. rs1137115A is predicted to create an exonic splicing suppressor site overlapping an exonic splicing enhancer (ESE) site in the first exon of CYP2A6, whereas rs28399435A is predicted to strengthen another adjacent ESE, potentially compensating for rs1137115A. Using an allelic expression assay to assess cDNAs produced from rs1137115 heterozygous liver biopsy samples, lower expression of the CYP2A6*1A allele is confirmed while CYP2A6*14 expression is found to be indistinguishable from that of rs1137115G alleles. Quantitative PCR assays to determine the relative abundance of spliced and unspliced or partially spliced CYP2A6 mRNAs in liver biopsy samples show that *1A/*1A homozygotes have a significantly lower ratio, due to both a reduction in spliced forms and an increase in unspliced or partially spliced CYP2A6. These results show the importance of common genetic variants that effect exonic splicing suppressor and ESEs to explain human variation regarding clinically-relevant phenotypes.
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Bough KJ, Lerman C, Rose JE, McClernon FJ, Kenny PJ, Tyndale RF, David SP, Stein EA, Uhl GR, Conti DV, Green C, Amur S. Biomarkers for smoking cessation. Clin Pharmacol Ther 2013; 93:526-38. [PMID: 23588313 PMCID: PMC3772534 DOI: 10.1038/clpt.2013.57] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
One way to enhance therapeutic development is through the identification and development of evaluative tools such as biomarkers. This review focuses on putative diagnostic, pharmacodynamic, and predictive biomarkers for smoking cessation. These types of biomarkers may be used to more accurately diagnose a disease, personalize treatment, identify novel targets for drug discovery, and enhance the efficiency of drug development. Promising biomarkers are presented across a range of approaches including metabolism, genetics, and neuroimaging. A preclinical viewpoint is also offered, as are analytical considerations and a regulatory perspective summarizing a pathway toward biomarker qualification.
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Affiliation(s)
- K J Bough
- Division of Pharmacotherapies and Medical Consequences, National Institute on Drug Abuse, Bethesda, Maryland, USA.
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Dempsey DA, Sambol NC, Jacob P, Hoffmann E, Tyndale RF, Fuentes-Afflick E, Benowitz NL. CYP2A6 genotype but not age determines cotinine half-life in infants and children. Clin Pharmacol Ther 2013; 94:400-6. [PMID: 23714690 PMCID: PMC3820275 DOI: 10.1038/clpt.2013.114] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 05/19/2013] [Indexed: 01/08/2023]
Abstract
The formation of cotinine, the main proximate metabolite and a biomarker of nicotine exposure, is mediated primarily by cytochrome P450 (CYP)2A6. Our aim was to determine whether higher cotinine levels in young children exposed to secondhand smoke (SHS) are a result of age-related differences in pharmacokinetics. Forty-nine participants, aged 2-84 months, received oral deuterium-labeled cotinine, with daily urine samples for up to 10 days for cotinine half-life measurement. DNA from saliva was used for CYP2A6 genotyping. The estimate of half-life using a mixed-effect model was 17.9 h (95% confidence interval: 16.5, 19.3), similar to that reported in adults. There was no statistically significant effect of sex, race, age, or weight. Children with normal-activity CYP2A6*1/*1 genotypes had a shorter half-life than those with one or two reduced-activity variant alleles. Our data suggest that higher cotinine levels in SHS-exposed young children as compared with adults are due to greater SHS exposure rather than to different cotinine pharmacokinetics.
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Affiliation(s)
- D A Dempsey
- Division of Clinical Pharmacology and Experimental Therapeutics, Medical Service, San Francisco General Hospital Medical Center, San Francisco, California, USA
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Zhu AZX, Renner CC, Hatsukami DK, Swan GE, Lerman C, Benowitz NL, Tyndale RF. The ability of plasma cotinine to predict nicotine and carcinogen exposure is altered by differences in CYP2A6: the influence of genetics, race, and sex. Cancer Epidemiol Biomarkers Prev 2013; 22:708-18. [PMID: 23371292 DOI: 10.1158/1055-9965.epi-12-1234-t] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Cotinine, a nicotine metabolite, is a biomarker of tobacco, nicotine, and carcinogen exposure. However, a given cotinine level may not represent the same tobacco exposure; for example, African-Americans have higher cotinine levels than Caucasians after controlling for exposure. METHODS Cotinine levels are determined by the amount of cotinine formation and the rate of cotinine removal, which are both mediated by the enzyme CYP2A6. Because CYP2A6 activity differs by sex (estrogen induces CYP2A6) and genotype, their effect on cotinine formation and removal was measured in nonsmoking Caucasians (Study 1, n = 181) infused with labeled nicotine and cotinine. The findings were then extended to ad libitum smokers (Study 2, n = 163). RESULTS Study 1: Reduced CYP2A6 activity altered cotinine formation less than cotinine removal resulting in ratios of formation to removal of 1.31 and 1.12 in CYP2A6 reduced and normal metabolizers (P = 0.01), or 1.39 and 1.12 in males and females (P = 0.001), suggesting an overestimation of tobacco exposure in slower metabolizers. Study 2: Cotinine again overestimated tobacco and carcinogen exposure by 25% or more in CYP2A6 reduced metabolizers (≈2-fold between some genotypes) and in males. CONCLUSIONS In people with slower relative to faster CYP2A6 activity, cotinine accumulates resulting in substantial differences in cotinine levels for a given tobacco exposure. IMPACT Cotinine levels may be misleading when comparing those with differing CYP2A6 genotypes within a race, between races with differing frequencies of CYP2A6 gene variants (i.e., African-Americans have higher frequencies of reduced function variants contributing to their higher cotinine levels), or between the sexes.
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Affiliation(s)
- Andy Z X Zhu
- Departments of Psychiatry, Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
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Zhu AZ, Binnington MJ, Renner CC, Lanier AP, Hatsukami DK, Stepanov I, Watson CH, Sosnoff CS, Benowitz NL, Tyndale RF. Alaska Native smokers and smokeless tobacco users with slower CYP2A6 activity have lower tobacco consumption, lower tobacco-specific nitrosamine exposure and lower tobacco-specific nitrosamine bioactivation. Carcinogenesis 2013; 34:93-101. [PMID: 23027621 PMCID: PMC3534190 DOI: 10.1093/carcin/bgs306] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 09/18/2012] [Accepted: 09/23/2012] [Indexed: 11/15/2022] Open
Abstract
Nicotine, the psychoactive ingredient in tobacco, is metabolically inactivated by CYP2A6 to cotinine. CYP2A6 also activates procarcinogenic tobacco-specific nitrosamines (TSNA). Genetic variation in CYP2A6 is known to alter smoking quantity and lung cancer risk in heavy smokers. Our objective was to investigate how CYP2A6 activity influences tobacco consumption and procarcinogen levels in light smokers and smokeless tobacco users. Cigarette smokers (n = 141), commercial smokeless tobacco users (n = 73) and iqmik users (n = 20) were recruited in a cross-sectional study of Alaska Native people. The participants' CYP2A6 activity was measured by both endophenotype and genotype, and their tobacco and procarcinogen exposure biomarker levels were also measured. Smokers, smokeless tobacco users and iqmik users with lower CYP2A6 activity had lower urinary total nicotine equivalents (TNE) and (methylnitrosamino)-1-(3)pyridyl-1-butanol (NNAL) levels (a biomarker of TSNA exposure). Levels of N-nitrosonornicotine (NNN), a TSNA metabolically bioactivated by CYP2A6, were higher in smokers with lower CYP2A6 activities. Light smokers and smokeless tobacco users with lower CYP2A6 activity reduce their tobacco consumption in ways (e.g. inhaling less deeply) that are not reflected by self-report indicators. Tobacco users with lower CYP2A6 activity are exposed to lower procarcinogen levels (lower NNAL levels) and have lower procarcinogen bioactivation (as indicated by the higher urinary NNN levels suggesting reduced clearance), which is consistent with a lower risk of developing smoking-related cancers. This study demonstrates the importance of CYP2A6 in the regulation of tobacco consumption behaviors, procarcinogen exposure and metabolism in both light smokers and smokeless tobacco users.
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Affiliation(s)
- Andy Z.X. Zhu
- Centre for Addiction and Mental Health, Departments of Psychiatry, Pharmacology and Toxicology, University of Toronto, Toronto M5S 1A8, Ontario
| | - Matthew J. Binnington
- Centre for Addiction and Mental Health, Departments of Psychiatry, Pharmacology and Toxicology, University of Toronto, Toronto M5S 1A8, Ontario
| | - Caroline C. Renner
- Alaska Native Medical Center, Cardiology Research and Program Development, Anchorage, AK, USA
| | - Anne P. Lanier
- Alaska Native Medical Center, Cardiology Research and Program Development, Anchorage, AK, USA
| | | | - Irina Stepanov
- Division of Environmental Health Sciences and Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Clifford H. Watson
- United States Centers for Disease Control and Prevention, Atlanta, GA, USA and
| | - Connie S. Sosnoff
- United States Centers for Disease Control and Prevention, Atlanta, GA, USA and
| | - Neal L. Benowitz
- Division of Clinical Pharmacology, Departments of Medicine, Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
| | - Rachel F. Tyndale
- To whom correspondence should be addressed. Tel: +1 416 978 6374; Fax: +1 416 978 6395; E-mail:
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Uno T, Obe Y, Ogura C, Goto T, Yamamoto K, Nakamura M, Kanamaru K, Yamagata H, Imaishi H. Metabolism of 7-ethoxycoumarin, safrole, flavanone and hydroxyflavanone by cytochrome P450 2A6 variants. Biopharm Drug Dispos 2012; 34:87-97. [DOI: 10.1002/bdd.1825] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 10/16/2012] [Accepted: 10/23/2012] [Indexed: 12/13/2022]
Affiliation(s)
- Tomohide Uno
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Yuichiro Obe
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Chika Ogura
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Tatsushi Goto
- Functional Analysis of Environmental Genes, Research Center for Environmental Genomics; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Kohei Yamamoto
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Masahiko Nakamura
- Department of Bioscience and Biotechnology, Faculty of Bioenvironmental Science; Kyoto Gakuen University; 1-1 Nanjo, Sogabe; Kameoka; Kyoto; 621-8555; Japan
| | - Kengo Kanamaru
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Hiroshi Yamagata
- Laboratory of Biological Chemistry, Department of Biofunctional Chemistry, Faculty of Agriculture; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
| | - Hiromasa Imaishi
- Functional Analysis of Environmental Genes, Research Center for Environmental Genomics; Kobe University; Nada-ku; Kobe; Hyogo; 657-8501; Japan
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Ferguson CS, Miksys S, Palmour RM, Tyndale RF. Differential Effects of Nicotine Treatment and Ethanol Self-Administration on CYP2A6, CYP2B6 and Nicotine Pharmacokinetics in African Green Monkeys. J Pharmacol Exp Ther 2012; 343:628-37. [DOI: 10.1124/jpet.112.198564] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Bloom AJ, Harari O, Martinez M, Madden PAF, Martin NG, Montgomery GW, Rice JP, Murphy SE, Bierut LJ, Goate A. Use of a predictive model derived from in vivo endophenotype measurements to demonstrate associations with a complex locus, CYP2A6. Hum Mol Genet 2012; 21:3050-62. [PMID: 22451501 DOI: 10.1093/hmg/dds114] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This study demonstrates a novel approach to test associations between highly heterogeneous genetic loci and complex phenotypes. Previous investigations of the relationship between Cytochrome P450 2A6 (CYP2A6) genotype and smoking phenotypes made comparisons by dividing subjects into broad categories based on assumptions that simplify the range of function of different CYP2A6 alleles, their numerous possible diplotype combinations and non-additive allele effects. A predictive model that translates CYP2A6 diplotype into a single continuous variable was previously derived from an in vivo metabolism experiment in 189 European Americans. Here, we apply this model to assess associations between genotype, inferred nicotine metabolism and smoking behaviors in larger samples without direct nicotine metabolism measurements. CYP2A6 genotype is not associated with nicotine dependence, as defined by the Fagerström Test of Nicotine Dependence, demonstrating that cigarettes smoked per day (CPD) and nicotine dependence have distinct genetic correlates. The predicted metric is significantly associated with CPD among African Americans and European American dependent smokers. Individual slow metabolizing genotypes are associated with lower CPD, but the predicted metric is the best predictor of CPD. Furthermore, optimizing the predictive model by including additional CYP2A6 alleles improves the fit of the model in an independent data set and provides a novel method of predicting the functional impact of alleles without direct metabolism measurements. Lastly, comprehensive genotyping and in vivo metabolism data are used to demonstrate that genome-wide significant associations between CPD and single nucleotide polymorphisms are the result of synthetic associations.
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Affiliation(s)
- A Joseph Bloom
- Department of Psychiatry, Washington University School of Medicine, 660 South Euclid, Saint Louis, MO 63119, USA.
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Gold AB, Lerman C. Pharmacogenetics of smoking cessation: role of nicotine target and metabolism genes. Hum Genet 2012; 131:10.1007/s00439-012-1143-9. [PMID: 22290489 PMCID: PMC3864572 DOI: 10.1007/s00439-012-1143-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 01/19/2012] [Indexed: 11/24/2022]
Abstract
Many smokers attempt to quit smoking but few are successful in the long term. The heritability of nicotine addiction and smoking relapse have been documented, and research is focused on identifying specific genetic influences on the ability to quit smoking and response to specific medications. Research in genetically modified cell lines and mice has identified nicotine acetylcholine receptor subtypes that mediate the pharmacological and behavioral effects of nicotine sensitivity and withdrawal. Human genetic association studies have identified single nucleotide polymorphisms (SNPs) in genes encoding nicotine acetylcholine receptor subunits and nicotine metabolizing enzymes that influence smoking cessation phenotypes. There is initial promising evidence for a role in smoking cessation for SNPs in the β2 and α5/α3/β4 nAChR subunit genes; however, effects are small and not consistently replicated. There are reproducible and clinically significant associations of genotypic and phenotypic measures of CYP2A6 enzyme activity and nicotine metabolic rate with smoking cessation as well as response to nicotine replacement therapies and bupropion. Prospective clinical trials to identify associations of genetic variants and gene-gene interactions on smoking cessation are needed to generate the evidence base for both medication development and targeted therapy approaches based on genotype.
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Affiliation(s)
- Allison B. Gold
- Center for Interdisciplinary Research on Nicotine Addiction, University of Pennsylvania, 3535 Market Street, Suite 4100, Philadelphia, PA 19104, USA
| | - Caryn Lerman
- Center for Interdisciplinary Research on Nicotine Addiction, University of Pennsylvania, 3535 Market Street, Suite 4100, Philadelphia, PA 19104, USA
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McGraw J, Waller D. Cytochrome P450 variations in different ethnic populations. Expert Opin Drug Metab Toxicol 2012; 8:371-82. [PMID: 22288606 DOI: 10.1517/17425255.2012.657626] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Variability of drug response is an important consideration in clinical medicine. A major determinant of drug response variability is hepatic cytochrome P450 oxidase (CYP450)-mediated drug metabolism. Advances in genetics permits genotyping large numbers of patients to identify single nucleotide polymorphisms (SNPs) which may result in variant CYP450 enzyme expression and/or activity. New SNPs with functional impacts are constantly being identified which further explain variability in CYP450 phenotype. AREAS COVERED The racial/ethnic distribution of selected CYP450 (CYP1A2, P2C8/9/19, 2D6 and 3A4/5) SNPs are reviewed with an emphasis on the agreement between genotype and phenotype. The reader will gain insight into the SNP distribution by racial/ethnic group and the corresponding relationship between important, highly prevalent, SNPs and their impact on metabolic phenotype. EXPERT OPINION Racial/ethnic differences in metabolic phenotype can be explained by differences in SNP distribution. However, overlap in substrate specificity, linkage disequilibrium and previously unidentified SNPs have made phenotypic characterization difficult for CYP3A4/5 and 2C8/9. Studies utilizing newly identified, highly prevalent, racially stratified SNPs and their impact on CYP isoform-specific metabolism will provide new answers.
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Affiliation(s)
- Joseph McGraw
- Concordia University Wisconsin, School of Pharmacy, 12800 N. Lakeshore Drive, Mequon, WI 53022, USA.
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Kohli U, Pandharipande P, Muszkat M, Sofowora GG, Friedman EA, Scheinin M, Wood AJJ, Ely EW, Tyndale RF, Choi L, Stein CM, Kurnik D. CYP2A6 genetic variation and dexmedetomidine disposition. Eur J Clin Pharmacol 2012; 68:937-42. [PMID: 22271297 DOI: 10.1007/s00228-011-1208-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 12/28/2011] [Indexed: 11/25/2022]
Abstract
PURPOSE There is a large interindividual variability in dexmedetomidine dose requirements for sedation of patients in intensive care units (ICU). Cytochrome P450 2A6 (CYP2A6) mediates an important route of dexmedetomidine metabolism, and genetic variation in CYP2A6 affects the clearance of other substrate drugs. We examined whether CYP2A6 genotypes affect dexmedetomidine disposition. METHODS In 43 critically ill ICU patients receiving dexmedetomidine infusions adjusted to achieve the desired level of sedation, we determined a median of five plasma dexmedetomidine concentrations each. Forty subjects were genotyped for five common CYP2A6 alleles and grouped into normal (n = 33), intermediate (n = 5), and slow metabolizers (n = 2). RESULTS Using a Bayesian hierarchical nonlinear mixture model, estimated dexmedetomidine clearance was 49.1 L/h (posterior mean; 95% credible interval 41.4-57.6 L/h). There were no significant differences in dexmedetomidine clearance among normal, intermediate, and slow CYP2A6 metabolizer groups. CONCLUSION Genetic variation in CYP2A6 does not appear to be an important determinant of dexmedetomidine clearance in ICU patients.
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Affiliation(s)
- Utkarsh Kohli
- Departments of Medicine and Pharmacology, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA
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Lee IS, Kim D. Polymorphic metabolism by functional alterations of human cytochrome P450 enzymes. Arch Pharm Res 2011; 34:1799-816. [PMID: 22139682 DOI: 10.1007/s12272-011-1103-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 08/24/2011] [Indexed: 10/14/2022]
Abstract
The study of cytochrome P450 pharmacogenomics is of particular interest because of its promise in the development of rational means to optimize drug therapy with respect to patient's genotype to ensure maximum efficacy with minimal adverse effects. Drug metabolizing P450 enzymes are polymorphic and are the main phase I enzymes responsible for the metabolism of clinical drugs. Therefore, polymorphisms in the P450s have the most impact on the fate of clinical drugs in phase I metabolism since almost 80% of drugs in use today are metabolized by these enzymes. Predictive genotyping for P450 enzymes for a more effective therapy will be routine for specific drugs in the future. In this review, we discuss the current knowledge of polymorphic metabolism by functional alterations in nonsynonymous SNPs of P450 1A2, 2A6, 2C8, 2C9, 2C19, 2D6, and 3A4 enzymes.
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Affiliation(s)
- Im-Soon Lee
- Department of Biological Sciences and Center for Biotechnology Research in UBITA, Konkuk University, Seoul 143-701, Korea
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Cho MH, Castaldi PJ, Wan ES, Siedlinski M, Hersh CP, Demeo DL, Himes BE, Sylvia JS, Klanderman BJ, Ziniti JP, Lange C, Litonjua AA, Sparrow D, Regan EA, Make BJ, Hokanson JE, Murray T, Hetmanski JB, Pillai SG, Kong X, Anderson WH, Tal-Singer R, Lomas DA, Coxson HO, Edwards LD, MacNee W, Vestbo J, Yates JC, Agusti A, Calverley PMA, Celli B, Crim C, Rennard S, Wouters E, Bakke P, Gulsvik A, Crapo JD, Beaty TH, Silverman EK. A genome-wide association study of COPD identifies a susceptibility locus on chromosome 19q13. Hum Mol Genet 2011; 21:947-57. [PMID: 22080838 DOI: 10.1093/hmg/ddr524] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The genetic risk factors for chronic obstructive pulmonary disease (COPD) are still largely unknown. To date, genome-wide association studies (GWASs) of limited size have identified several novel risk loci for COPD at CHRNA3/CHRNA5/IREB2, HHIP and FAM13A; additional loci may be identified through larger studies. We performed a GWAS using a total of 3499 cases and 1922 control subjects from four cohorts: the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); the Normative Aging Study (NAS) and National Emphysema Treatment Trial (NETT); Bergen, Norway (GenKOLS); and the COPDGene study. Genotyping was performed on Illumina platforms with additional markers imputed using 1000 Genomes data; results were summarized using fixed-effect meta-analysis. We identified a new genome-wide significant locus on chromosome 19q13 (rs7937, OR = 0.74, P = 2.9 × 10(-9)). Genotyping this single nucleotide polymorphism (SNP) and another nearby SNP in linkage disequilibrium (rs2604894) in 2859 subjects from the family-based International COPD Genetics Network study (ICGN) demonstrated supportive evidence for association for COPD (P = 0.28 and 0.11 for rs7937 and rs2604894), pre-bronchodilator FEV(1) (P = 0.08 and 0.04) and severe (GOLD 3&4) COPD (P = 0.09 and 0.017). This region includes RAB4B, EGLN2, MIA and CYP2A6, and has previously been identified in association with cigarette smoking behavior.
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Affiliation(s)
- Michael H Cho
- Channing Laboratory, Brigham & Women’s Hospital, Boston, MA 02115, USA.
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Systematic review of the relationship between the 3-hydroxycotinine/cotinine ratio and cigarette dependence. Psychopharmacology (Berl) 2011; 218:313-22. [PMID: 21597990 DOI: 10.1007/s00213-011-2341-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 04/30/2011] [Indexed: 10/18/2022]
Abstract
RATIONALE Individual differences in the rate of nicotine metabolism (RNM) could be related to dependence and success in stopping smoking. A range of studies have examined RNM measured by the ratio of trans-3'-hydroxycotinine and cotinine in body fluids (the ratio). A systematic review of this literature is needed to draw conclusions and identify gaps in evidence. OBJECTIVE The aim of this study is to review evidence on the association of the ratio to cigarette dependence and its role in individual tailoring of smoking cessation pharmacotherapy. RESULTS We reviewed 27 studies of the ratio related to its reliability, validity, and relationship to dependence. The ratio is a reasonably accurate proxy for RNM. There is little evidence that the ratio is related to questionnaire measures of dependence, though the existing data are limited and the ratio has been linked to smoking at night and to some aspects of smoking topography. The ratio is also only weakly associated with cigarette consumption. Its relationship to the severity of withdrawal symptoms seems also weak at best, but limited data exist. One study suggests the ratio predicts outcome of unaided quitting. Importantly, the ratio seems to predict responses both to NRT and bupropion, and thus could guide pharmacotherapy. CONCLUSIONS The evidence that the ratio is related to smoking behaviours and to cigarette dependence is limited, but the ratio seems to influence treatment response to two stop smoking medications. Further studies of the relationship between the ratio and cigarette dependence and trials of ratio-guided pharmacotherapy are needed.
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The contribution of common CYP2A6 alleles to variation in nicotine metabolism among European-Americans. Pharmacogenet Genomics 2011; 21:403-16. [PMID: 21597399 DOI: 10.1097/fpc.0b013e328346e8c0] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To study the association between cytochrome P450 2A6 (CYP2A6) genotype and metabolism of nicotine to cotinine, identify functional polymorphisms, and develop a predictive genetic model of nicotine metabolism. METHODS The conversion of deuterated (D2)-nicotine to D2-cotinine was quantified in 189 European-Americans and the contribution of CYP2A6 genotype to variability in first-pass nicotine metabolism was assessed. Specifically, (i) single time point measures of D2-cotinine/(D2-cotinine+D2-nicotine) after oral administration were used as a metric of CYP2A6 activity; (ii) the impact of CYP2A6 haplotype was treated as acting multiplicatively; (iii) parameter estimates were calculated for all haplotypes in the subject pool, defined by a set of polymorphisms previously reported to affect function, including gene copy number; and (iv) a minimum number of predictive polymorphisms were justified to be included in the model based on statistical evidence of differences between haplotypes. RESULTS The final model includes seven polymorphisms and fits the phenotype, 30-min after D2-nicotine oral administration, with R=0.719. The predictive power of the model is robust: parameter estimates calculated in men (n=89) predict the phenotype in women (n=100) with R=0.758 and vice versa with R=0.617; estimates calculated in current smokers (n=102) predict the phenotype in former-smokers (n=86) with R=0.690 and vice versa with R=0.703. Comparisons of haplotypes also demonstrate that CYP2A6*12 is a loss-of-function allele indistinguishable from CYP2A6*4 and CYP2A6*2 and that the CYP2A6*1B 5'-untranslated region conversion has negligible impact on metabolism. After controlling for CYP2A6 genotype, modest associations were found between increased metabolism and both female sex (P=4.8×10) and current smoking (P=0.02). CONCLUSION Among European-Americans, seven polymorphisms in the CYP2A6 gene explain the majority of variability in the metabolism of nicotine to cotinine after oral administration. Parameters determined from this in-vivo experiment can be used to predict nicotine metabolism based on CYP2A6 genotype.
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Desta Z, Kreutz Y, Nguyen AT, Li L, Skaar T, Kamdem LK, Henry NL, Hayes DF, Storniolo AM, Stearns V, Hoffmann E, Tyndale RF, Flockhart DA. Plasma letrozole concentrations in postmenopausal women with breast cancer are associated with CYP2A6 genetic variants, body mass index, and age. Clin Pharmacol Ther 2011; 90:693-700. [PMID: 21975350 DOI: 10.1038/clpt.2011.174] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The associations between plasma letrozole concentrations and CYP2A6 and CYP3A5 genetic variants were tested in the Exemestane and Letrozole Pharmacogenomics (ELPH) trial. ELPH is a multicenter, open-label prospective clinical trial in women randomly assigned (n≈250 in each arm) to receive 2 years of treatment with either oral letrozole (2.5 mg/day) or oral exemestane (25 mg/day). CYP2A6 and CYP3A showed effects on letrozole metabolism in vitro. DNA samples were genotyped for variants in the CYP2A6 and CYP3A5 genes. Plasma letrozole concentrations showed high interpatient variability (>10-fold) and were associated significantly with CYP2A6 genotypes (P<0.0001), body mass index (BMI) (P<0.0001), and age (P=0.0035). However, CYP3A5 genotypes showed no association with plasma letrozole concentrations. These data suggest that CYP2A6 is the principal clearance mechanism for letrozole in vivo. CYP2A6 metabolic status, along with BMI and age, may serve as a biomarker of the efficacy of letrozole treatment or a predictor of adverse effects.
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Affiliation(s)
- Z Desta
- Department of Medicine, Indiana University, Indianapolis, Indiana, USA.
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