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Gallardo-Cóndor J, Naranjo P, Atarihuana S, Coello D, Guevara-Ramírez P, Flores-Espinoza R, Burgos G, López-Cortés A, Cabrera-Andrade A. Population-Specific Distribution of TPMT Deficiency Variants and Ancestry Proportions in Ecuadorian Ethnic Groups: Towards Personalized Medicine. Ther Clin Risk Manag 2023; 19:1005-1018. [PMID: 38050617 PMCID: PMC10693761 DOI: 10.2147/tcrm.s432856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Accepted: 11/06/2023] [Indexed: 12/06/2023] Open
Abstract
Purpose Thiopurine S-methyltransferase (TPMT) is an enzyme that metabolizes purine analogs, agents used in the treatment of acute lymphoblastic leukemia. Improper drug metabolism leads to toxicity in chemotherapy patients and reduces treatment effectiveness. TPMT variants associated with reduced enzymatic activity vary across populations. Therefore, studying these variants in heterogeneous populations, such as Ecuadorians, can help identify molecular causes of deficiency for this enzyme. Methods We sequenced the entire TPMT coding region in 550 Ecuadorian individuals from Afro-Ecuadorian, Indigenous, Mestizo, and Montubio ethnicities. Moreover, we conducted an ancestry analysis using 46 informative ancestry markers. Results We identified 8 single nucleotide variants in the coding region of TPMT. The most prevalent alleles were TPMT*3A, TPMT*3B, and TPMT*3C, with frequencies of 0.055, 0.012, and 0.015, respectively. Additionally, we found rare alleles TPMT*4 and TPMT*8 with frequencies of 0.005 and 0.003. Correlating the ancestry proportions with TPMT-deficient genotypes, we observed that the Native American ancestry proportion influenced the distribution of the TPMT*1/TPMT*3A genotype (OR = 5.977, p = 0.002), while the contribution of African ancestral populations was associated with the TPMT*1/TPMT*3C genotype (OR = 9.769, p = 0.003). The rates of TPMT-deficient genotypes observed in Mestizo (f = 0.121) and Indigenous (f = 0.273) groups provide evidence for the influence of Native American ancestry and the prevalence of the TPMT*3A allele. In contrast, although Afro-Ecuadorian groups demonstrate similar deficiency rates (f = 0.160), the genetic factors involved are associated with contributions from African ancestral populations, specifically the prevalent TPMT*3C allele. Conclusion The distribution of TPMT-deficient variants offers valuable insights into the populations under study, underscoring the necessity for genetic screening strategies to prevent thiopurine toxicity events among Latin American minority groups.
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Affiliation(s)
| | - Pablo Naranjo
- Facultad de Ingeniería y Ciencias Aplicadas, Universidad de Las Américas, Quito, Ecuador
| | - Sebastián Atarihuana
- Facultad de Ingeniería y Ciencias Aplicadas, Universidad de Las Américas, Quito, Ecuador
| | - Dayana Coello
- Laboratorios de Investigación, Universidad de Las Américas, Quito, Ecuador
| | - Patricia Guevara-Ramírez
- Centro de Investigación Genética y Genómica, Facultad de Ciencias de la Salud Eugenio Espejo, Universidad UTE, Quito, Ecuador
| | - Rodrigo Flores-Espinoza
- Laboratório de Diagnóstico por DNA (LDD), Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Germán Burgos
- One Health Research Group, Facultad de Medicina, Universidad de Las Américas, Quito, Ecuador
- Grupo de Medicina Xenomica, Instituto de Ciencias Forenses, Universidad de Santiago de Compostela, Satiago de Compostela, Spain
| | - Andrés López-Cortés
- Cancer Research Group (CRG), Faculty of Medicine, Universidad de Las Américas, Quito, Ecuador
- Latin American Network for the Implementation and Validation of Clinical Pharmacogenomics Guidelines (RELIVAF-CYTED), Madrid, Spain
| | - Alejandro Cabrera-Andrade
- Escuela de Enfermería, Facultad de Ciencias de la Salud, Universidad de Las Américas, Quito, Ecuador
- Grupo de Bio-Quimioinformática, Universidad de Las Américas, Quito, Ecuador
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Mora Y, Villegas C, Mora YM, Moreno N. TPMT gene polymorphisms (c.238G>C, c.460G>A and c.719A>G) in a healthy Venezuelan population. Pharmacogenomics 2023; 24:219-225. [PMID: 36946340 DOI: 10.2217/pgs-2022-0187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023] Open
Abstract
Background: The presence of polymorphisms in the TPMT gene is associated with adverse effects in patients treated with standard doses of thiopurine drugs. Scientific evidence recognizes significant ethnic differences in their frequencies and how their early identification can prevent clinical complications. Methods: 150 healthy residents of Aragua, Venezuela were enrolled. The SNPs c.460G>A and c.719A>G were detected by PCR-restriction fragment length polymorphism assay and c.238G>C by allele-specific PCR. Results: All genotype polymorphisms were heterozygous. TPMT*1/*3A, TPMT*1/*3C and TPMT*1/*2 genotypes were found in 4.0, 2.0 and 0.7%, respectively. Conclusion: 6.7% of individuals have an intermediate TPMT activity. These findings support the importance of prior genotyping of TPMT in Venezuelan patients who require thiopurine drug therapy.
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Affiliation(s)
- Yuselin Mora
- Instituto de Investigaciones Biomédicas 'Dr. Francisco J. Triana Alonso' (BIOMED) - Sección de Polimorfismos Genómicos, Facultad de Ciencias de la Salud, Universidad de Carabobo, Sede Aragua, Maracay, 2102, Venezuela
| | - Cecilia Villegas
- Instituto de Investigaciones Biomédicas 'Dr. Francisco J. Triana Alonso' (BIOMED) - Sección de Polimorfismos Genómicos, Facultad de Ciencias de la Salud, Universidad de Carabobo, Sede Aragua, Maracay, 2102, Venezuela
| | - Yamile M Mora
- Instituto de Investigaciones Biomédicas 'Dr. Francisco J. Triana Alonso' (BIOMED) - Sección de Polimorfismos Genómicos, Facultad de Ciencias de la Salud, Universidad de Carabobo, Sede Aragua, Maracay, 2102, Venezuela
| | - Nancy Moreno
- Instituto de Investigaciones Biomédicas 'Dr. Francisco J. Triana Alonso' (BIOMED) - Sección de Polimorfismos Genómicos, Facultad de Ciencias de la Salud, Universidad de Carabobo, Sede Aragua, Maracay, 2102, Venezuela
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Alsous M, Yousef AM, Abdel Jalil M, Zawiah M, Yacoub S, Momani D, Gharabli A, Omar S, Rihani R. Genetic Polymorphism of Thiopurine S-methyltransferase in Children with Acute Lymphoblastic Leukemia in Jordan. Asian Pac J Cancer Prev 2018; 19:199-205. [PMID: 29373914 PMCID: PMC5844618 DOI: 10.22034/apjcp.2018.19.1.199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Background and Aims: It has been demonstrated that homozygote and heterozygote mutant allele carriers for thiopurine S-methyltransferase (TPMT) are at high risk of developing myelosuppression after receiving standard doses of 6-mercaptopurine (6-MP). The aim of this study was to determine the frequency of TPMT deficient alleles in children with acute lymphoblastic leukemia (ALL) in Jordan and to compare it with other ethnic groups. Methods: We included 52 ALL childhood cases from King Hussein Cancer Research Center in Jordan. Genotyping of the rs1800460, rs1800462, and rs1142345 SNPs was performed by polymerase chain reaction (PCR) followed by sequencing. Comparisons were made with historical data for controls and for both volunteers and cases from other middle-eastern countries. Results: Mutant TPMT alleles were present in 3.8% (2/52) of patients. Allelic frequencies were 1.0% for both TPMT*B and TPMT*C. None of the patients were heterozygous or homozygous for TPMT*3A or TPMT *2. We did not find statistically significant differences in the distribution of mutant alleles between Jordan and other middle-eastern countries for both healthy volunteers or ALL patients. Conclusions: The overall frequency of TPMT mutant alleles was low and did not exhibit differences compared to other middle-eastern countries, including Jordanian studies assessing TPMT mutant alleles in healthy volunteers. The current results question the value of TPMT genotyping in the Jordanian population.
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Affiliation(s)
- Mervat Alsous
- Department of Clinical Pharmacy and Therapeutics, Faculty of Pharmacy, Applied Science Private University, Amman, Jordan.
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Ramirez-Florencio M, Jiménez-Morales S, Barbosa-Cobos RE, López-Cano DJ, Ramírez-Bello J. High frequency of mutant thiopurine S-methyltransferase genotypes in Mexican patients with systemic lupus erythematosus and rheumatoid arthritis. Clin Rheumatol 2017; 37:963-970. [PMID: 29264794 DOI: 10.1007/s10067-017-3955-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 11/24/2017] [Accepted: 12/12/2017] [Indexed: 12/20/2022]
Abstract
Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are treated with immunosuppressive purine analogs, 6-mercaptopurine/6-thioguanine/azathiopurine, which are inactivated by thiopurine S-methyltransferase (TPMT). Non-synonymous polymorphisms in TPMT are associated with increased risk of adverse effects in patients treated with thiopurines. This study aimed to determine the frequency of the most common mutant TPMT alleles in Mexican patients with SLE (a prototype autoimmune disease) and RA (one of the most common autoimmune diseases in Mexico). Five hundred fifty-three consecutive patients from Central Mexico with SLE (178) and RA (375) were included. Subjects were genotyped to identify TPMT*2 (rs1800462), TPMT*3A (rs1800460 and rs1142345), TPMT*3B (rs1800460), and TPMT*3C (rs1142345) mutant alleles. DNA samples were assayed with the 5' exonuclease technique and TaqMan probes. Mutant alleles were detected in 6.2 and 5.2% of SLE and RA cases, respectively. Of note, 12.4% of SLE cases and 10.1% of RA cases carried mutant genotypes. Among those, the null genotype (TPMT*2/*3A, 0.3%) and the TPMT*3B (0.5%) and TPMT*3C (1.0%) alleles were found in RA, but not SLE cases. Mexican SLE cases displayed the highest frequency of mutant TPMT genotypes worldwide. TPMT genotyping should be performed for Mexican patients with SLE and RA before prescribing purine analogs.
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Affiliation(s)
- Mireya Ramirez-Florencio
- Laboratorio de Genómica del Cáncer, Instituto Nacional de Medicina Genómica, Periferico Sur 4809, Tlalpan, Arenal Tepepan, 14610, Mexico City, CDMX, Mexico
| | - Silvia Jiménez-Morales
- Laboratorio de Genómica del Cáncer, Instituto Nacional de Medicina Genómica, Periferico Sur 4809, Tlalpan, Arenal Tepepan, 14610, Mexico City, CDMX, Mexico.
| | | | - Daniela Josabeth López-Cano
- Unidad de Investigación en Enfermedades Endócrinas y Metabólicas, Hospital Juárez de México, Av. Instituto Politécnico Nacional No. 5160 Delegación Gustavo A. Madero, C.P. 07760, Mexico City, D.F., Mexico
| | - Julian Ramírez-Bello
- Unidad de Investigación en Enfermedades Endócrinas y Metabólicas, Hospital Juárez de México, Av. Instituto Politécnico Nacional No. 5160 Delegación Gustavo A. Madero, C.P. 07760, Mexico City, D.F., Mexico.
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Roy LM, Zur RM, Uleryk E, Carew C, Ito S, Ungar WJ. Thiopurine S-methyltransferase testing for averting drug toxicity in patients receiving thiopurines: a systematic review. Pharmacogenomics 2016; 17:633-56. [PMID: 27020704 PMCID: PMC4931919 DOI: 10.2217/pgs.16.12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AIM Thiopurine S-methyltransferase (TPMT) testing is used in patients receiving thiopurines to identify enzyme deficiencies and risk for adverse drug reactions. It is uncertain whether genotyping is superior to phenotyping. The objectives were to conduct a systematic review of TPMT-test performance studies. MATERIALS & METHODS Electronic and grey literature sources were searched for studies reporting test performance compared with a reference standard. Sixty-six eligible studies were appraised for quality. RESULTS Thirty phenotype-genotype and six phenotype-phenotype comparisons were of high quality. The calculated sensitivity and specificity for genotyping to identify a homozygous mutation ranged from 0.0-100.0% and from 97.8-100.0%, respectively. CONCLUSION Clinical decision-makers require high-quality evidence of clinical validity and clinical utility of TPMT genotyping to ensure appropriate use in patients.
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Affiliation(s)
- Lilla M Roy
- Child Health Evaluative Sciences, The Hospital for Sick Children Research Institute, Toronto, Canada
| | - Richard M Zur
- Child Health Evaluative Sciences, The Hospital for Sick Children Research Institute, Toronto, Canada
| | - Elizabeth Uleryk
- Library Services, The Hospital for Sick Children, Toronto, Canada
| | - Chris Carew
- Centre for Genetic Medicine, The Hospital for Sick Children, Toronto, Canada
| | - Shinya Ito
- Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, Toronto, Canada
- Departments of Pharmacology & Pharmacy, Faculty of Medicine Department of Paediatrics, University of Toronto, Canada
| | - Wendy J Ungar
- Child Health Evaluative Sciences, The Hospital for Sick Children Research Institute, Toronto, Canada
- Institute for Health Policy, Management & Evaluation, University of Toronto, Canada
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Marsh S, King CR, Van Booven DJ, Revollo JY, Gilman RH, McLeod HL. Pharmacogenomic assessment of Mexican and Peruvian populations. Pharmacogenomics 2016; 16:441-8. [PMID: 25916516 DOI: 10.2217/pgs.15.10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Clinically relevant polymorphisms often demonstrate population-specific allele frequencies. Central and South America remain largely uncategorized in the context of pharmacogenomics. MATERIALS & METHODS We assessed 15 polymorphisms from 12 genes (ABCB1 3435C>T, ABCG2 Q141K, CYP1B1*3, CYP2C19*2, CYP3A4*1B, CYP3A5*3C, ERCC1 N118N, ERCC2 K751Q, GSTP1 I105V, TPMT 238G>C, TPMT 460G>A, TPMT 719A>G, TYMS TSER, UGT1A1*28 and UGT1A1 -3156G>A) in 81 Peruvian and 95 Mexican individuals. RESULTS Six polymorphism frequencies differed significantly between the two populations: ABCB1 3435C>T, CYP1B1*3, GSTP1 I105V, TPMT 460G>A, UGT1A1*28 and UGT1A1 -3156G>A. The pattern of observed allele frequencies for all polymorphisms could not be accurately estimated from any single previously studied population. CONCLUSION This highlights the need to expand the scope of geographic data for use in pharmacogenomics studies.
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Affiliation(s)
- Sharon Marsh
- Faculty of Pharmacy & Pharmaceutical Sciences, 3142F Katz Centre for Pharmacy & Health Research, University of Alberta, Edmonton, AB T6G 2E1, Canada
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Chaudhary R, Singh B, Kumar M, Gakhar SK, Saini AK, Parmar VS, Chhillar AK. Role of single nucleotide polymorphisms in pharmacogenomics and their association with human diseases. Drug Metab Rev 2015; 47:281-90. [PMID: 25996670 DOI: 10.3109/03602532.2015.1047027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Global statistical data shed light on an alarming trend that every year thousands of people die due to adverse drug reactions as each individual responds in a different way to the same drug. Pharmacogenomics has come up as a promising field in drug development and clinical medication in the past few decades. It has emerged as a ray of hope in preventing patients from developing potentially fatal complications due to adverse drug reactions. Pharmacogenomics also minimizes the exposure to drugs that are less/non-effective and sometimes even found toxic for patients. It is well reported that drugs elicit different responses in different individuals due to variations in the nucleotide sequences of genes encoding for biologically important molecules (drug-metabolizing enzymes, drug targets and drug transporters). Single nucleotide polymorphisms (SNPs), the most common type of polymorphism found in the human genome is believed to be the main reason behind 90% of all types of genetic variations among the individuals. Therefore, pharmacogenomics may be helpful in answering the question as to how inherited differences in a single gene have a profound effect on the mobilization and biological action of a drug. In the present review, we have discussed clinically relevant examples of SNP in associated diseases that can be utilized as markers for "better management of complex diseases" and attempted to correlate the drug response with genetic variations. Attention is also given towards the therapeutic consequences of inherited differences at the chromosomal level and how associated drug disposition and/or drug targets differ in various diseases as well as among the individuals.
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Affiliation(s)
| | | | | | - Surendra K Gakhar
- b Centre for Medical Biotechnology, Maharshi Dayanand University , Rohtak , Haryana , India
| | - Adesh K Saini
- c Department of Biotechnology , Shoolini University of Biotechnology and Management Sciences , Solan , Himachal Pradesh , India , and
| | - Virinder S Parmar
- d Bioorganic Laboratory, Department of Chemistry , University of Delhi , Delhi , India
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Zeglam HB, Benhamer A, Aboud A, Rtemi H, Mattardi M, Saleh SS, Bashein A, Enattah N. Polymorphisms of the thiopurine S-methyltransferase gene among the Libyan population. Libyan J Med 2015; 10:27053. [PMID: 25819542 PMCID: PMC4376936 DOI: 10.3402/ljm.v10.27053] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 03/02/2015] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Thiopurine S-methyltransferase (TPMT) is a cytosolic enzyme that catalyses the S-methylation of 6-mercaptopurine and azathioprine. Low activity phenotypes are correlated with polymorphism in the TPMT gene. Patients with low or undetectable TMPT activity could develop severe myelosuppression when they are treated with standard doses of thiopurine drugs. Since ethnic differences in the TPMT gene polymorphism have been demonstrated worldwide, assessing it in the Libyan population is worthwhile. METHODS We investigated TPMT gene polymorphism in a total of 246 Libyan healthy adult blood donors from three different Libyan regions (Tripoli, Yefren, and Tawargha) and 50 children with acute lymphoblastic leukaemia (ALL). We used polymerase chain reaction restriction length polymorphism (PCR-RFLP) and allele-specific PCR-based assays to analyse the TPMT gene for the variants *2 c.238 G>C, *3A (c.460 G>A and c.719 A>G), *3B (c.460 G>A), and *3C (c.719 A>G). RESULTS Our results show that the TPMT variants associated with low enzymatic activity were detected in 3.25% (8 in 246) of adult Libyan individuals and the frequency of total mutant alleles was 1.63%. Heterozygous genotypes were TPMT*3A in three subjects (0.61%) and TPMT*3C in five subjects (1.02%). No TPMT*2 and TPMT*3B allelic variants and no homozygous or compound heterozygous mutant alleles were detected. The normal allele (wild-type) was found in 98.4% of the adult individuals studied. No mutant alleles were detected among the 50 children who had ALL. CONCLUSIONS We report on the presence of the TPMT*3C and *3A mutant alleles in the Libyan population. Therefore, monitoring the patients to be treated with doses of thiopurine drugs for TPMT variants is worthwhile to avoid the development of severe myelosuppression.
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Affiliation(s)
- Hamza Ben Zeglam
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya
| | - Abdrazak Benhamer
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya
| | - Adel Aboud
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya
| | - Haitem Rtemi
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya
| | - Meftah Mattardi
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya
| | - Saleh Suleiman Saleh
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya
| | - Abdullah Bashein
- Department of Biochemistry, Faculty of Medicine, University of Tripoli, Tripoli, Libya
| | - Nabil Enattah
- Department of Genetic Engineering, Biotechnology Research Center (BTRC), Twisha, Tripoli, Libya; ;
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Abstract
The antileukemic mechanisms of 6-mercaptopurine (6MP) and methotrexate (MTX) maintenance therapy are poorly understood, but the benefits of several years of myelosuppressive maintenance therapy for acute lymphoblastic leukemia are well proven. Currently, there is no international consensus on drug dosing. Because of significant interindividual and intraindividual variations in drug disposition and pharmacodynamics, vigorous dose adjustments are needed to obtain a target degree of myelosuppression. As the normal white blood cell counts vary by patients' ages and ethnicity, and also within age groups, identical white blood cell levels for 2 patients may not reflect the same treatment intensity. Measurements of intracellular levels of cytotoxic metabolites of 6MP and MTX can identify nonadherent patients, but therapeutic target levels remains to be established. A rise in serum aminotransferase levels during maintenance therapy is common and often related to high levels of methylated 6MP metabolites. However, except for episodes of hypoglycemia, serious liver dysfunction is rare, the risk of permanent liver damage is low, and aminotransferase levels usually normalize within a few weeks after discontinuation of therapy. 6MP and MTX dose increments should lead to either leukopenia or a rise in aminotransferases, and if neither is experienced, poor treatment adherence should be considered. The many genetic polymorphisms that determine 6MP and MTX disposition, efficacy, and toxicity have precluded implementation of pharmacogenomics into treatment, the sole exception being dramatic 6MP dose reductions in patients who are homozygous deficient for thiopurine methyltransferase, the enzyme that methylates 6MP and several of its metabolites. In conclusion, maintenance therapy is as important as the more intensive and toxic earlier treatment phases, and often more challenging. Ongoing research address the applicability of drug metabolite measurements for dose adjustments, extensive host genome profiling to understand diversity in treatment efficacy and toxicity, and alternative thiopurine dosing regimens to improve therapy for the individual patient.
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Farfan MJ, Salas C, Canales C, Silva F, Villarroel M, Kopp K, Torres JP, Santolaya ME, Morales J. Prevalence of TPMT and ITPA gene polymorphisms and effect on mercaptopurine dosage in Chilean children with acute lymphoblastic leukemia. BMC Cancer 2014; 14:299. [PMID: 24774509 PMCID: PMC4012712 DOI: 10.1186/1471-2407-14-299] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 04/23/2014] [Indexed: 10/26/2022] Open
Abstract
BACKGROUND Mercaptopurine (6-MP) plays a pivotal role in treatment of childhood acute lymphoblastic leukemia (ALL); however, interindividual variability in toxicity of this drug due to genetic polymorphism in 6-MP metabolizing enzymes has been described. We determined the prevalence of the major genetic polymorphisms in 6-MP metabolizing enzymes in Chilean children with ALL. METHODS 103 Chilean pediatric patients with a confirmed diagnosis of ALL were enrolled. DNA was isolated from whole blood and genetic polymorphism in thiopurine S-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) coding genes were detected by polymorphism chain reaction-restriction fragment length (PCR-RFLP) assay. RESULTS The total frequency of variant TPMT alleles was 8%. TPMT*2, TPMT*3A and TPMT*3B alleles were found in 0%, 7%, and 1% of patients, respectively. For ITPA, the frequency of P32T allele was 3%. We did not observe any homozygous variant for TPMT and ITPA alleles. We also analyzed a subgroup of 40 patients who completed the maintenance phase of ALL treatment, and we found that patients carrying a TPMT gene variant allele required a significantly lower median cumulative dosage and median daily dosage of 6-MP than patients carrying wild type alleles. CONCLUSION TMPT genotyping appears an important tool to further optimize 6-MP treatment design in Chilean patients with ALL.
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Affiliation(s)
- Mauricio J Farfan
- Departamento de Pediatría, Centro de Estudios Moleculares, Facultad de Medicina, Universidad de Chile, Antonio Varas 360, Santiago, Chile.
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Garrido C, Santizo VG, Müllers P, Soriano DR, Avila GB, Dean M, Jimenez-Morales S. Frequency of thiopurine S-methyltransferase mutant alleles in indigenous and admixed Guatemalan patients with acute lymphoblastic leukemia. Med Oncol 2013; 30:474. [PMID: 23377985 DOI: 10.1007/s12032-013-0474-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 01/08/2013] [Indexed: 12/11/2022]
Abstract
Thiopurine S-methyltransferase (TPMT) polymorphisms affect the enzyme's activity and are predictive for the efficacy and toxicity of thiopurine treatment of acute lymphoblastic leukemia (ALL), autoimmune diseases and organ transplants. Because inter-ethnic differences in the distribution of these polymorphisms have been documented, we sequenced the TMPT gene in 95 Guatemalans, yet identified no new alleles. We also determined the frequency of the TPMT 2, 3A, 3B and 3C alleles in 270 admixed and 177 indigenous pediatric patients with ALL and healthy subjects from Guatemala using TaqMan assays and DNA sequencing. Among the 447 subjects genotyped, 10.0 % of the ALL cases and 13.6 % of the healthy controls were heterozygous for one of the four TPMT variants screened. The genotype frequencies in ALL and control populations were 0.7 and 1.7 % for TPMT 1/ 2, 7.4 and 10 % for TPMT 1/3A, 0.3 and 0 % for TPMT 1/B, and 1.5 and 1.1 % for TPMT 1/C, respectively (p = 0.30). No statistically significant differences between admixed and indigenous ALL (p = 0.67) or controls (p = 0.41) groups were detected; however, 17 % of the admixed healthy group bore one TPMT mutant allele, and they have one of the highest reported frequencies of TPMT mutant allele carriers. Because of the clinical implications of these variants for therapeutic response, TPMT allele testing should be considered in all Guatemalan patients to reduce adverse side-effects from thiopurine drug treatments.
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Affiliation(s)
- Claudia Garrido
- Unidad Nacional de Oncología Pediátrica, Guatemala City, Guatemala
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Umamaheswaran G, Krishna Kumar D, Kayathiri D, Rajan S, Shewade DG, Dkhar SA, Manjunath S, Ushakiran P, Reneega G, Ritushree K, Adithan C. Inter and intra-ethnic differences in the distribution of the molecular variants of TPMT, UGT1A1 and MDR1 genes in the South Indian population. Mol Biol Rep 2012; 39:6343-51. [PMID: 22318545 DOI: 10.1007/s11033-012-1456-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 01/23/2012] [Indexed: 01/18/2023]
Abstract
Molecular variants of polymorphic drug metabolizing enzymes and drug transporters are attributed to differences in individual's therapeutic response and drug toxicity in different populations. We sought to determine the genotype and allele frequencies of polymorphisms for major phase II drug-metabolizing enzymes (TPMT, UGT1A1) and drug transporter (MDR1) in South Indians. Allelic variants of TPMT (*2,*3A,*3B,*3C & *8), UGT1A1 (TA)6>7 and MDR1 (2677G>T/A & 3435C>T) were evaluated in 450-608 healthy South Indian subjects. Genomic DNA was extracted by phenol-chloroform method and genotype was determined by PCR-RFLP, qRT-PCR, allele specific PCR, direct sequencing and SNaPshot techniques. The frequency distributions of TPMT, UGT1A1 and MDR1 gene polymorphisms were compared between the individual 4 South Indian populations viz., Tamilian, Kannadiga, Andhrite and Keralite. The combined frequency distribution of the South Indian populations together, was also compared with that of other major populations. The allele frequencies of TPMT*3C, UGT1A1 (TA)7, MDR1 2677T, 2677A and 3435T were 1.2, 39.8, 60.3, 3.7, and 61.6% respectively. The other variant alleles such as TPMT*2, *3A, *3B and *8 were not identified in the South Indian population. Sub-population analysis showed that the distribution of UGT1A1 (TA)6>7 and MDR1 allelic variants differed between the four ethnic groups. However, the frequencies of TPMT*3C allele were similar in the four South Indian populations. The distribution of TPMT, UGT1A1 and MDR1 gene polymorphisms of the South Indian population was significantly different from other populations.
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Affiliation(s)
- Gurusamy Umamaheswaran
- ICMR Centre for Advance Research in Pharmacogenomics, Department of Pharmacology, JIPMER, Pondicherry, India.
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14
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Taja-Chayeb L, Vidal-Millán S, Gutiérrez O, Ostrosky-Wegman P, Dueñas-González A, Candelaria M. Thiopurine S-methyltransferase Gene (TMPT) polymorphisms in a Mexican population of healthy individuals and leukemic patients. Med Oncol 2007; 25:56-62. [DOI: 10.1007/s12032-007-9002-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Accepted: 08/10/2007] [Indexed: 01/26/2023]
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15
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Rossino R, Vincis C, Alves S, Prata MJ, Macis MD, Nucaro AL, Schirru E, Congia M. Frequency of the thiopurine S-methyltransferase alleles in the ancient genetic population isolate of Sardinia. J Clin Pharm Ther 2006; 31:283-7. [PMID: 16789994 DOI: 10.1111/j.1365-2710.2006.00736.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Thiopurine S-methyltransferase (TPMT) is an enzyme involved in the normal metabolic inactivation of thiopurine drugs. Patients with intermediate or no TPMT activity are at risk of toxicity after receiving standard doses of thiopurine drugs and it was shown that inter-individual differences in response to these drugs is largely determined by genetic variation at the TPMT locus. OBJECTIVE This study was designed to investigate in the Sardinian population the frequency distribution of four of the most common variants accounting for TPMT deficiency and to conduct comparative analyses with other populations in order to obtain insights into the main factors that have shaped diversity at the TPMT locus in Sardinia. METHODS DNA was extracted in 259 Sardinians and the frequencies of allelic variants of TPMT were determined using polymerase chain reaction-restriction fragment length polymorphism technique. RESULTS Among the 259 Sardinians genotyped, 6.95% were found to be heterozygous for one of four TPMT variants screened; for each variant the frequency estimate was 1.74%, 0.58%, 0.39% and 0.77% for TPMT*2, TPMT*3A, TPMT*3B and TPMT*3C respectively. CONCLUSIONS Although Sardinia does not show reduced diversity at the TPMT locus, the spectrum of TPMT allele frequencies affords evidence of remarkable influence of genetic drift and founder effects throughout its population history. In the broad context of the European TPMT diversity, the Sardinians come out as outliers, an observation consistent with previous genetic inferences that Sardinia has features of a genetic isolate.
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Affiliation(s)
- R Rossino
- Dipartimento Di Scienze Biomediche e Biotecnologie, Università Di Cagliari, and Ospedale Microcitemico, Cagliari, Italy.
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