Polymorphisms for aromatic amine metabolism in humans: relevance for human carcinogenesis

The Roles of Neutrophil-Derived Myeloperoxidase (MPO) in Diseases: The New Progress

Myeloperoxidase (MPO) is a heme-containing peroxidase, mainly expressed in neutrophils and, to a lesser extent, in monocytes. MPO is known to have a broad bactericidal ability via catalyzing the reaction of Cl- with H2O2 to produce a strong oxidant, hypochlorous acid (HOCl). However, the overproduction of MPO-derived oxidants has drawn attention to its detrimental role, especially in diseases characterized by acute or chronic inflammation. Broadly speaking, MPO and its derived oxidants are involved in the pathological processes of diseases mainly through the oxidation of biomolecules, which promotes inflammation and oxidative stress. Meanwhile, some researchers found that MPO deficiency or using MPO inhibitors could attenuate inflammation and tissue injuries. Taken together, MPO might be a promising target for both prognostic and therapeutic interventions. Therefore, understanding the role of MPO in the progress of various diseases is of great value. This review provides a comprehensive analysis of the diverse roles of MPO in the progression of several diseases, including cardiovascular diseases (CVDs), neurodegenerative diseases, cancers, renal diseases, and lung diseases (including COVID-19). This information serves as a valuable reference for subsequent mechanistic research and drug development.

Methylenediphenyl diisocyanate lysine conjugates in the urine of workers exposed to methylenediphenyl diisocyanate

Diisocyanates have long been a leading cause of occupational asthma. As control often relies on personal protective equipment and there is the potential for skin uptake, biological monitoring is often used to assess worker exposure. Current routine biological monitoring methods do not distinguish between a diisocyanate and the corresponding diamine exposure in urine samples; therefore, a specific urinary biomarker is desirable. Urine samples were obtained from a group of workers exposed to methylenediphenyl diisocyanate (MDI) where aerosol generation was unlikely. Lysine conjugates of MDI were extracted from urine by solid phase extraction; analysis was performed by liquid chromatography tandem mass spectrometry. Acetylated MDI-lysine (acMDI-Lys) conjugates were detected in 73% of samples tested from persons with exposure to MDI compared to 93% of samples that were positive for methylene dianiline (MDA) in hydrolysed urine. There was a weak but significant positive correlation between the two biomarkers (r² = 0.377). This is the first report detecting and quantifying acMDI-Lys in the urine of workers exposed to MDI, and acMDI-Lys may be a useful non-invasive biomarker in discriminating between MDI and MDA exposures.

DNA damage, DNA repair and carcinogenicity: Tobacco smoke versus electronic cigarette aerosol

The allure of tobacco smoking is linked to the instant gratification provided by inhaled nicotine. Unfortunately, tobacco curing and burning generates many mutagens including more than 70 carcinogens. There are two types of mutagens and carcinogens in tobacco smoke (TS): direct DNA damaging carcinogens and procarcinogens, which require metabolic activation to become DNA damaging. Recent studies provide three new insights on TS-induced DNA damage. First, two major types of TS DNA damage are induced by direct carcinogen aldehydes, cyclic-1,N2-hydroxy-deoxyguanosine (γ-OH-PdG) and α-methyl-1, N2-γ-OH-PdG, rather than by the procarcinogens, polycyclic aromatic hydrocarbons and aromatic amines. Second, TS reduces DNA repair proteins and activity levels. TS aldehydes also prevent procarcinogen activation. Based on these findings, we propose that aldehydes are major sources of TS induce DNA damage and a driving force for carcinogenesis. E-cigarettes (E-cigs) are designed to deliver nicotine in an aerosol state, without burning tobacco. E-cigarette aerosols (ECAs) contain nicotine, propylene glycol and vegetable glycerin. ECAs induce O6-methyl-deoxyguanosines (O6-medG) and cyclic γ-hydroxy-1,N2--propano-dG (γ-OH-PdG) in mouse lung, heart and bladder tissues and causes a reduction of DNA repair proteins and activity in lungs. Nicotine and nicotine-derived nitrosamine ketone (NNK) induce the same types of DNA adducts and cause DNA repair inhibition in human cells. After long-term exposure, ECAs induce lung adenocarcinoma and bladder urothelial hyperplasia in mice. We propose that E-cig nicotine can be nitrosated in mouse and human cells becoming nitrosamines, thereby causing two carcinogenic effects, induction of DNA damage and inhibition of DNA repair, and that ECA is carcinogenic in mice. Thus, this article reviews the newest literature on DNA adducts and DNA repair inhibition induced by nicotine and ECAs in mice and cultured human cells, and provides insights into ECA carcinogenicity in mice.

Weighted Gene Co-expression Network Analysis Identified a Novel Thirteen-Gene Signature Associated With Progression, Prognosis, and Immune Microenvironment of Colon Adenocarcinoma Patients

Colon adenocarcinoma (COAD) is one of the most common malignant tumors and has high migration and invasion capacity. In this study, we attempted to establish a multigene signature for predicting the prognosis of COAD patients. Weighted gene co-expression network analysis and differential gene expression analysis methods were first applied to identify differentially co-expressed genes between COAD tissues and normal tissues from the Cancer Genome Atlas (TCGA)-COAD dataset and GSE39582 dataset, and a total of 309 overlapping genes were screened out. Then, our study employed TCGA-COAD cohort as the training dataset and an independent cohort by merging the GES39582 and GSE17536 datasets as the testing dataset. After univariate and multivariate Cox regression analyses were performed for these overlapping genes and overall survival (OS) of COAD patients in the training dataset, a 13-gene signature was constructed to divide COAD patients into high- and low-risk subgroups with significantly different OS. The testing dataset exhibited the same results utilizing the same predictive signature. The area under the curve of receiver operating characteristic analysis for predicting OS in the training and testing datasets were 0.789 and 0.868, respectively, which revealed the enhanced predictive power of the signature. Multivariate Cox regression analysis further suggested that the 13-gene signature could independently predict OS. Among the 13 prognostic genes, NAT1 and NAT2 were downregulated with deep deletions in tumor tissues in multiple COAD cohorts and exhibited significant correlations with poorer OS based on the GEPIA database. Notably, NAT1 and NAT2 expression levels were positively correlated with infiltrating levels of CD8+ T cells and dendritic cells, exhibiting a foundation for further research investigating the antitumor immune roles played by NAT1 and NAT2 in COAD. Taken together, the results of our study showed that the 13-gene signature could efficiently predict OS and that NAT1 and NAT2 could function as biomarkers for prognosis and the immune response in COAD.

Analysis of urinary metabolites of polycyclic aromatic hydrocarbons in precarious workers of highly exposed occupational scenarios in Mexico

Exposure to polycyclic aromatic hydrocarbons (PAHs) is a risk factor for human health. Workers are a vulnerable group due to their high exposure and therefore require special attention to mitigation measurements; however, some groups of workers are especially vulnerable, precarious workers. The objective of this research was to evaluate mixtures of hydroxylated PAHs (OH-PAHs) in precarious workers in Mexico. The following activities were evaluated: (i) brickmakers (TER), stonemasons (ESC), indigenous workers (TOC) and mercury miners (CAM). Ten OH-PAHS were analyzed: 1-hydroxynaphtalene and 2-hydroxynaphtalene; 2-,3- and 9-hydroxyfluorene; 1-,2-,3- and 4-hydroxyphenanthrene; and 1-hydroxypyrene in urine by GC-MS, chemical fingerprints of the sites were established by multivariate analysis. One hundred forty-nine precarious workers participated in the study. The populations presented total OH-PAHs concentrations of 9.20 (6.65-97.57), 14.8 (9.32-18.85), 15.7 (6.92-195.0), and 101.2 (8.02-134.4) μg/L for CAM, ESC, TER, and TOC, respectively (median (IQR)). The results of the multivariate analysis indicate that the indigenous population presented a different fingerprint compared to the three scenarios. The chemical fingerprints among the brickmakers and mercury mining population were similar. The results of the concentrations were similar and in some metabolites higher than workers in occupations classified as carcinogenic by the IARC; therefore, the control of exposure in these occupations acquires great importance and surveillance through biological monitoring of OH-PAHs should be applied to better estimate exposure in these working populations.

Characterization of N-(2,6-dimethylphenyl)hydroxylamine adducts of 2'-deoxyguanosine under weakly basic conditions

Aromatic amines are a class of chemical carcinogens that are activated by cytochrome P450 enzymes to form arylhydroxylamines that are conjugated to form N-acetoxyarylamines or N-sulfonyloxyarylamines. These conjugates undergo N-O bond cleavage to become reactive nitrenium ions that may form DNA adducts. Numerous studies in the past using N-acetoxyarylamines to investigate DNA adduct formation were conducted, however, less is known in regard to DNA adduct formation directly from arylhydroxylamines - especially under conditions that mimic the physiological conditions of cells such as weakly basic conditions. In this study, 2'-deoxyguanosine (dG) was exposed to N-(2,6-dimethylphenyl)hydroxylamine (2,6-DMPHA) and N-phenylhydroxylamine (PHA) at pH 7.4 without enzymes and analyzed by liquid chromatography high resolution mass spectrometry (LC-HRMS). 2,6-DMPHA exposure resulted in the production of relatively low amounts of adducts however the identities of at least six different adducts that were formed through reactions with carbon, nitrogen and oxygen of 2'-deoxyguanosine were proposed based upon different analytical approaches including HRMS CID fragmentation and NMR analyses. Contrastively, PHA exposure under identical conditions resulted in one adduct at the C8 position. It was concluded from these results and results of theoretical calculations that nitrenium ions produced from 2,6-DMPHA were relatively more stable resulting in longer nitrenium ion lifetimes which ultimately led to greater potential for 2,6-DMPHA nitrenium ions to react with multiple sites on dG.

Cometabolic degradation of chloramphenicol via a meta-cleavage pathway in a microbial fuel cell and its microbial community

The performance of a microbial fuel cell (MFC) in terms of degradation of chloramphenicol (CAP) was investigated. Approximately 84% of 50mg/L CAP was degraded within 12h in the MFC. A significant interaction of pH, temperature, and initial CAP concentration was found on removal of CAP, and a maximum degradation rate of 96.53% could theoretically be achieved at 31.48°C, a pH of 7.12, and an initial CAP concentration of 106.37mg/L. Moreover, CAP was further degraded through a ring-cleavage pathway. The antibacterial activity of CAP towards Escherichia coli ATCC 25922 and Shewanella oneidensis MR-1 was largely eliminated by MFC treatment. High-throughput sequencing analysis indicated that Azonexus, Comamonas, Nitrososphaera, Chryseobacterium, Azoarcus, Rhodococcus, and Dysgonomonas were the predominant genera in the MFC anode biofilm. In conclusion, the MFC shows potential for the treatment of antibiotic residue-containing wastewater due to its high rates of CAP removal and energy recovery.

Bioactivation of Heterocyclic Aromatic Amines by UDP Glucuronosyltransferases

2-Amino-9H-pyrido[2,3-b]indole (AαC) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are carcinogenic heterocyclic aromatic amines (HAA) that arise during the burning of tobacco and cooking of meats. UDP-glucuronosyltransferases (UGT) detoxicate many procarcinogens and their metabolites. The genotoxic N-hydroxylated metabolite of AαC, 2-hydroxyamino-9H-pyrido[2,3-b]indole (HONH-AαC), undergoes glucuronidation to form the isomeric glucuronide (Gluc) conjugates N(2)-(β-d-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (AαC-HON(2)-Gluc) and O-(β-d-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (AαC-HN(2)-O-Gluc). AαC-HON(2)-Gluc is a stable metabolite but AαC-HN(2)-O-Gluc is a biologically reactive intermediate, which covalently adducts to DNA at levels that are 20-fold higher than HONH-AαC. We measured the rates of formation of AαC-HON(2)-Gluc and AαC-HN(2)-O-Gluc in human organs: highest activity occurred with liver and kidney microsomes, and lesser activity was found with colon and rectum microsomes. AαC-HN(2)-O-Gluc formation was largely diminished in liver and kidney microsomes, by niflumic acid, a selective inhibitor UGT1A9. In contrast, AαC-HON(2)-Gluc formation was less affected and other UGT contribute to N(2)-glucuronidation of HONH-AαC. UGT were reported to catalyze the formation of isomeric Gluc conjugates at the N(2) and N3 atoms of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP), the genotoxic metabolite of PhIP. However, we found that the N3-Gluc of HONH-PhIP also covalently bound to DNA at higher levels than HONH-PhIP. The product ion spectra of this Gluc conjugate acquired by ion trap mass spectrometry revealed that the Gluc moiety was linked to the oxygen atom of HONH-PhIP and not the N3 imidazole atom of the oxime tautomer of HONH-PhIP as was originally proposed. UGT1A9, an abundant UGT isoform expressed in human liver and kidney, preferentially forms the O-linked Gluc conjugates of HONH-AαC and HONH-PhIP as opposed to their detoxicated N(2)-Gluc isomers. The regioselective O-glucuronidation of HONH-AαC and HONH-PhIP, by UGT1A9, is a mechanism of bioactivation of these ubiquitous HAAs.

Caffeine Cytochrome P450 1A2 Metabolic Phenotype Does Not Predict the Metabolism of Heterocyclic Aromatic Amines in Humans

2-Amino-1-methylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) are carcinogenic heterocyclic aromatic amines (HAAs) formed in well-done cooked meats. Chemicals that induce cytochrome P450 (P450) 1A2, a major enzyme involved in the bioactivation of HAAs, also form in cooked meat. Therefore, well-done cooked meat may pose an increase in cancer risk because it contains both inducers of P450 1A2 and procarcinogenic HAAs. We examined the influence of components in meat to modulate P450 1A2 activity and the metabolism of PhIP and MeIQx in volunteers during a 4 week feeding study of well-done cooked beef. The mean P450 1A2 activity, assessed by caffeine metabolic phenotyping, ranged from 6.3 to 7.1 before the feeding study commenced and from 9.6 to 10.4 during the meat feeding period: the difference in means was significant (P < 0.001). Unaltered PhIP, MeIQx, and their P450 1A2 metabolites, N(2)-(β-1-glucosiduronyl)-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (HON-PhIP-N(2)-Gl); N3-(β-1-glucosiduronyl)-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (HON-PhIP-N3-Gl); 2-amino-3-methylimidazo-[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH); and 2-amino-8-(hydroxymethyl)-3-methylimidazo[4,5-f]quinoxaline (8-CH2OH-IQx) were measured in urine during days 2, 14, and 28 of the meat diet. Significant correlations were observed on these days between the levels of the unaltered HAAs and their oxidized metabolites, when expressed as percent of dose ingested or as metabolic ratios. However, there was no statistically significant correlation between the caffeine P450 1A2 phenotype and any urinary HAA biomarker. Although the P450 1A2 activity varied by greater than 20-fold among the subjects, there was a large intraindividual variation of the P450 1A2 phenotype and inconsistent responses to inducers of P450 1A2. The coefficient of variation of the P450 1A2 phenotype within-individual ranged between 1 to 112% (median = 40%) during the entire course of the study. The caffeine metabolic phenotype for P450 1A2 was a poor predictor of oxidative urinary metabolites of PhIP and MeIQx and may not be a reliable measure to assess the role of HAAs in cancer risk.

Tobacco smoking, polymorphisms in carcinogen metabolism enzyme genes, and risk of localized and advanced prostate cancer: results from the California Collaborative Prostate Cancer Study

The relationship between tobacco smoking and prostate cancer (PCa) remains inconclusive. This study examined the association between tobacco smoking and PCa risk taking into account polymorphisms in carcinogen metabolism enzyme genes as possible effect modifiers (9 polymorphisms and 1 predicted phenotype from metabolism enzyme genes). The study included cases (n = 761 localized; n = 1199 advanced) and controls (n = 1139) from the multiethnic California Collaborative Case-Control Study of Prostate Cancer. Multivariable conditional logistic regression was performed to evaluate the association between tobacco smoking variables and risk of localized and advanced PCa risk. Being a former smoker, regardless of time of quit smoking, was associated with an increased risk of localized PCa (odds ratio [OR] = 1.3; 95% confidence interval [CI] = 1.0-1.6). Among non-Hispanic Whites, ever smoking was associated with an increased risk of localized PCa (OR = 1.5; 95% CI = 1.1-2.1), whereas current smoking was associated with risk of advanced PCa (OR = 1.4; 95% CI = 1.0-1.9). However, no associations were observed between smoking intensity, duration or pack-year variables, and advanced PCa. No statistically significant trends were seen among Hispanics or African-Americans. The relationship between smoking status and PCa risk was modified by the CYP1A2 rs7662551 polymorphism (P-interaction = 0.008). In conclusion, tobacco smoking was associated with risk of PCa, primarily localized disease among non-Hispanic Whites. This association was modified by a genetic variant in CYP1A2, thus supporting a role for tobacco carcinogens in PCa risk.

N-acetyltransferase 2 status and gastric cancer risk: a meta-analysis

Case-control studies on the association between N-acetyltransferase 2 (NAT2) genotype and gastric cancer have provided either controversial or inconclusive results. In order to clarify the influence of NAT2 acetylation status on gastric cancer risk, a meta-analysis was undertaken. The primary outcome measure was the odds ratio (OR) for the risk of gastric cancer associated with the NAT2 genotype. The overall result showed that there was no statistically significant association between NAT2 status and gastric cancer risk (slow acetylation vs. rapid acetylation, OR = 1.10, 95 % confidence interval (CI) 0.97-1.25, p = 0.12). In the analysis stratified by East Asian ethnicity, a significant association was found between gastric cancer and the NAT2 genotype (slow acetylation vs. rapid acetylation, OR = 1.33, 95 % CI 1.11-1.59, p = 0.002). Our pooled data suggest that the NAT2 acetylation status has an effect on the risk of gastric cancer among East Asian populations.

Toxicogenomics and cancer susceptibility: advances with next-generation sequencing

The aim of this review is to comprehensively summarize the recent achievements in the field of toxicogenomics and cancer research regarding genetic-environmental interactions in carcinogenesis and detection of genetic aberrations in cancer genomes by next-generation sequencing technology. Cancer is primarily a genetic disease in which genetic factors and environmental stimuli interact to cause genetic and epigenetic aberrations in human cells. Mutations in the germline act as either high-penetrance alleles that strongly increase the risk of cancer development, or as low-penetrance alleles that mildly change an individual's susceptibility to cancer. Somatic mutations, resulting from either DNA damage induced by exposure to environmental mutagens or from spontaneous errors in DNA replication or repair are involved in the development or progression of the cancer. Induced or spontaneous changes in the epigenome may also drive carcinogenesis. Advances in next-generation sequencing technology provide us opportunities to accurately, economically, and rapidly identify genetic variants, somatic mutations, gene expression profiles, and epigenetic alterations with single-base resolution. Whole genome sequencing, whole exome sequencing, and RNA sequencing of paired cancer and adjacent normal tissue present a comprehensive picture of the cancer genome. These new findings should benefit public health by providing insights in understanding cancer biology, and in improving cancer diagnosis and therapy.

Lifestyle and colorectal cancer: A case-control study

A case-control study has been conducted to investigate the relationship between lifestyle and risk of colorectal cancer. Cases are one hundred patients diagnosed with colon and rectal cancer in Tokai University Hospital between 1986 and 1994. Three controls per case were individually matched by age, sex, local areas and date of health checkups at the Automated Multi-phasic Health Testing and Services (AMHTS ) Center of the hospital. The results were analyzed by multi-factorial logistic regression models. Positive history of maternal cancer, large consumption of alcohol, frequent consumption of potato products and white-collar job were predominant risk factors while frequent intake of seaweed was a protective factor. Frequent intakes of dairy foods and lack of exercise showed no significant tendency to increase risk of colorectal cancer. Smoking habits, intakes of meat and egg were shown not to be related to this disease. These findings suggest that family history of cancer and dietary factors play a key role in causation and prevention of colorectal cancer.

Toxicogenetics--cytochrome P450 microarray analysis in forensic cases focusing on morphine/codeine and diazepam

Genetic polymorphisms in cytochrome P 450 (CYP) enzymes could lead to a phenotype with altered enzyme activity. In pharmacotherapy, genotype-based dose recommendations achieved great importance for several drugs. In our pilot study, we ask if these genetic tests should be applied to forensic problems as a matter of routine. Starting from 2004 through 2008, we screened routine cases for samples where the relation of parent compound to metabolite(s) (P/M ratio), particularly morphine to codeine ratios and diazepam to its metabolites, was noticeable or not consistent with the information provided by the defendants. We found 11 samples with conspicuous results. These were analyzed for polymorphisms of the CYP 2D6 and 2C19 genes using the Roche AmpliChip Cytochrome P450 Genotyping test. If not previously conducted, a general unknown analysis by gas chromatography/mass spectrometry (GC/MS) was additionally carried out. For CYP 2D6, we found two cases with the genotype poor metabolizer (PM), three cases with heterozygote extensive metabolizer genotype classified as an intermediate metabolizer (IM) with probably reduced enzyme activities, but no ultrarapid metabolizer genotype. For CYP 2C19, two cases were characterized as IM phenotypes, with no PM found. Once we achieved no appropriate amounts of DNA, one case was excluded after GC/MS analysis. Only in one case could the polymorphism clearly explain the changes in drug metabolism. More frequently, a drug-drug interaction was thought to have a stronger impact. Additionally, our results suggest that IM genotypes may be more relevant than previously suspected. With respect to the small number of cases in which we thought a genotyping would be helpful, we conclude that the overall relevance of toxicogenetics in forensic problems is moderate. However, in some individual cases, a genotyping may provide new insight.

Metabolism and biomarkers of heterocyclic aromatic amines in molecular epidemiology studies: lessons learned from aromatic amines

Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct, and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels, and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs, and thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and emerging biomarkers of HAAs that may be implemented in molecular epidemiology studies are discussed.

Decolorization of the AO24 azo dye and reduction of toxicity and genotoxicity in trickling biofilters

Acid Orange 24 (AO24) dye was degraded in a trickling biofilter packed with peat and wood chips and inoculated with biomass from a petrochemical industry wastewater system. Different operating strategies were tested; in the first stage, two biofilters were operated independently--one non-aerated biofilter (passive) and the other with aeration-subsequently, the systems were operated serially, and effluent from the non-aerated biofilter was fed to the biofilter with aeration. This treatment train was used to test three different filtration velocities--0.141, 0.282, and 0.423 m/d. The results show that, when operating the systems with a dye charge of 0.035 kg AO24 m2/d and treating the effluent in a single step, good removal efficiencies of AO24 (95 and 89%), COD (63 and 53%), and acute toxicity (63 and 78%) were obtained in both biofilters (with and without air), although mutagenic and potentially carcinogenic intermediary compounds were not removed, because genotoxicity exhibits values higher than 2.0 units for the mutation rate. When using the non-aerated biofilter/aerated biofilter treatment train, it is possible to treat a dye charge 3 times greater (0.106 kg AO24 m2/d) and efficiently remove 98% AO24, 76% COD, 100% acute toxicity, and 100% genotoxicity, which indicates that, with this biological system, an advanced degree of biotransformation and mineralization of the azo dye AO24 is achieved.

Colon cancer chemopreventive activities of pomegranate ellagitannins and urolithins

Pomegranate juice derived ellagitannins and their intestinal bacterial metabolites, urolithins, inhibited TCDD-induced CYP1-mediated EROD activity in vitro with IC(50) values ranging from 56.7 microM for urolithin A to 74.8 microM for urolithin C. These compounds exhibited dose- and time-dependent decreases in cell proliferation and clonogenic efficiency of HT-29 cells. Inhibition of cell proliferation was mediated through cell cycle arrest in the G(0)/G(1) and G(2)/M stages of the cell cycle followed by induction of apoptosis. These results indicate that the ellagitannins and urolithins released in the colon upon consumption of pomegranate juice in considerable amounts could potentially curtail the risk of colon cancer development, by inhibiting cell proliferation and inducing apoptosis.

Basic properties and molecular mechanisms of exogenous chemical carcinogens

Exogenous chemical carcinogenesis is an extremely complex multifactorial process during which gene-environment interactions involving chronic exposure to exogenous chemical carcinogens (ECCs) and polymorphisms of cancer susceptibility genes add further complexity. We describe the properties and molecular mechanisms of ECCs that contribute to induce and generate cancer. A basic and specific property of many lipophilic organic ECCs including polycyclic aromatic hydrocarbons and polyhalogenated aromatic hydrocarbons is their ability to bioaccumulate in the adipose tissue from where they may be released in the blood circulation and target peripheral tissues for carcinogenesis. Many organic ECCs are procarcinogens and consequently need to be activated by the cytochrome P450 (CYP) system and/or other enzymes before they can adduct DNA and proteins. Because they contribute not only to the cocarcinogenic and promoting effects of many aromatic pollutants but also to their mutagenic effects, the aryl hydrocarbon receptor-activating and the inducible CYP systems are central to exogenous chemical carcinogenesis. Another basic property of ECCs is their ability to induce stable and bulky DNA adducts that cannot be simply repaired by the different repair systems. In addition, following ECC exposure, mutagenesis may also be caused indirectly by free-radical production and by epigenetic alterations. As a result of complex molecular interplays, direct and/or indirect mutagenesis may especially account for the carcinogenic effects of many exogenous metals and metalloids. Because of these molecular properties and action mechanisms, we conclude that ECCs could be major contributors to human cancer, with obviously great public health consequences.

Coffee intake, smoking, and pulmonary function in the Atherosclerosis Risk in Communities Study

Coffee contains polyphenolic antioxidants and caffeine, which may favorably affect pulmonary function. Therefore, the authors studied cross-sectional associations (1987-1989) between coffee intake and pulmonary function in the Atherosclerosis Risk in Communities Study, a population-based cohort study (analytic sample = 10,658). They also conducted analyses stratified by smoking status, since smoking is a strong risk factor for respiratory disease and could influence the effects of caffeine and antioxidants. Self-reported coffee intake was categorized as rare/never, <7 cups/week, 1 cup/day, 2-3 cups/day, and >or=4 cups/day. Pulmonary function was characterized by the spirometric measures forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV(1)). After adjustment for demographic factors, lifestyle characteristics, and dietary factors, pulmonary function values increased across increasing categories of coffee consumption in never and former smokers but not in current smokers. In never or former smokers who consumed >or=4 cups of coffee daily, FVC and FEV(1) were 2%-3% greater than in never or former smokers who rarely/never consumed coffee (P(trend) values: in never smokers, 0.04 for FVC and 0.07 for FEV(1); in former smokers, <0.001 for FVC and <0.001 for FEV(1)). These data show a possible beneficial effect of coffee (or a coffee ingredient) on pulmonary function, but it appears to be limited to nonsmokers.

Phase I metabolic genes and risk of lung cancer: multiple polymorphisms and mRNA expression

Polymorphisms in genes coding for enzymes that activate tobacco lung carcinogens may generate inter-individual differences in lung cancer risk. Previous studies had limited sample sizes, poor exposure characterization, and a few single nucleotide polymorphisms (SNPs) tested in candidate genes. We analyzed 25 SNPs (some previously untested) in 2101 primary lung cancer cases and 2120 population controls from the Environment And Genetics in Lung cancer Etiology (EAGLE) study from six phase I metabolic genes, including cytochrome P450s, microsomal epoxide hydrolase, and myeloperoxidase. We evaluated the main genotype effects and genotype-smoking interactions in lung cancer risk overall and in the major histology subtypes. We tested the combined effect of multiple SNPs on lung cancer risk and on gene expression. Findings were prioritized based on significance thresholds and consistency across different analyses, and accounted for multiple testing and prior knowledge. Two haplotypes in EPHX1 were significantly associated with lung cancer risk in the overall population. In addition, CYP1B1 and CYP2A6 polymorphisms were inversely associated with adenocarcinoma and squamous cell carcinoma risk, respectively. Moreover, the association between CYP1A1 rs2606345 genotype and lung cancer was significantly modified by intensity of cigarette smoking, suggesting an underling dose-response mechanism. Finally, increasing number of variants at CYP1A1/A2 genes revealed significant protection in never smokers and risk in ever smokers. Results were supported by differential gene expression in non-tumor lung tissue samples with down-regulation of CYP1A1 in never smokers and up-regulation in smokers from CYP1A1/A2 SNPs. The significant haplotype associations emphasize that the effect of multiple SNPs may be important despite null single SNP-associations, and warrants consideration in genome-wide association studies (GWAS). Our findings emphasize the necessity of post-GWAS fine mapping and SNP functional assessment to further elucidate cancer risk associations.

NQO1, MPO, and the risk of lung cancer: a HuGE review

The aim of this study is to summarize the available molecular epidemiologic studies of lung cancer and metabolic genes, such as NAD(P)H quinone reductase 1 (NQO1) and myeloperoxidase (MPO). NQO1 plays a dual role in the detoxification and activation of procarcinogens whereas MPO has Phase I activity by converting lipophilic carcinogens into hydrophilic forms. Variant genotypes of both NQO1 Pro187 Ser and MPO G-463A polymorphisms may be related to low enzyme activity. The Pro/Ser and Ser/Ser genotypes combined of NQO1 was significantly associated with decreased risk of lung cancer in Japanese [random effects odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.56-0.88] among whom the variant allele is common. The variant genotype of MPO was associated with decreased risk of lung cancer among Caucasians (random effects OR = 0.70, 95% CI = 0.47-1.04). Gene-environment interactions in both polymorphisms may be hampered by inaccurate categorization of tobacco exposure. Evidence on gene-gene interactions is extremely limited. As lung cancer is a multifactorial disease, an improved understanding of such interactions may help identify individuals at risk for developing lung cancer. Such a study should include larger sample size and other polymorphisms in the metabolism of tobacco-derived carcinogens and address interactions with smoking status. The effects of polymorphisms are best represented by their haplotypes. In future studies on lung cancer, the development of haplotype-based approaches will facilitate the evaluation of haplotypic effects, either for selected polymorphisms physically close to each other or for multiple genes within the same drug-metabolism pathway.

Heterologous expression and characterization of wild-type human cytochrome P450 1A2 without conventional N-terminal modification in Escherichia coli

In this study, wild-type human CYP1A2 without the conventional N-terminal modification (second codon GCT) or the truncation of the N-terminal hydrophobic region was functionally expressed in Escherichia coli. Its enzymatic properties were compared with N-terminally modified CYP1A2. Although modified CYP1A2 is almost all high-spin, some wild-type CYP1A2 shifted to low-spin. Spectral binding titrations with several ligands could be performed with wild-type enzyme, but not with modified enzyme. Kinetic parameters for several substrates were similar for the two CYP1A2 enzymes. However, the oxidation rates of phenacetin by modified enzyme were approximately 2-fold higher than those by wild-type enzyme. The intermolecular isotope effects were approximately 2 for phenacetin O-deethylation catalyzed by both enzymes. However, the wild-type enzyme, but not the modified enzyme, increased C-hydroxylation when O-deethylation rates were lowered by deuterium substitution. Molecular switching indicates that phenacetin rotates within the active site of wild-type enzyme and suggests a looser conformation in the active site of the wild-type enzyme than of the modified enzyme. These results reveal that the overall enzymatic properties of wild-type CYP1A2 enzyme are quite similar to those of modified CYP1A2, although its active site environment seems to differ from that of the modified enzyme.

Dose-dependent reduction of 3,2'-dimethyl-4-aminobiphenyl-derived DNA adducts in colon and liver of rats administered celecoxib

Colon cancer is second leading cause of cancer-related deaths in Western countries. Diet and smoking, which contain aromatic and heterocyclic amines, are major risk factors for colon cancer. Colorectal cancers have a natural history of long latency and therefore provide ample opportunities for effective chemoprevention. 3,2'-Dimethyl-4-aminobiphenyl (DMABP) is an experimental aromatic amine that causes cancer in rat colon and serves as an experimental model for arylamine and heterocyclic amine mutagens derived from diet and smoking. In this study, we investigated the effects of celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor on DMABP-induced DNA adduct formation in rat liver and colon. Male F-344 rats (5-week old) were provided free access to modified AIN-76A rat chow containing 0 (control), 500, 1000, or 1500 ppm celecoxib. Two weeks later, the rats received a subcutaneous injection of 100mg/kg DMABP in peanut oil. Two days after DMABP treatment, the rats were killed and DMABP-derived adducts were analyzed in colon and liver DNA by butanol extraction-mediated (32)P-postlabeling. Two major DNA adducts, identified as dG-C8-DMABP and dG-N(2)-DMABP, were detected in liver and colon of rats treated with DMABP. These DNA adducts were diminished approximately 35-40% with 500 ppm and 65-70% with 1,000 ppm celecoxib. In the colon, no further decline in DNA adducts was observed at 1500 ppm. The same DMABP-DNA adducts also were detected in the liver and were also diminished by celecoxib treatment. The reduction in DMABP-DNA adduct levels in celecoxib-treated animals provides further support for celecoxib as a chemopreventive agent for colorectal cancer.

Polymorphism of selected enzymes involved in detoxification and biotransformation in relation to lung cancer

Available data indicate that there are significant differences in individual susceptibility to lung cancer within the human population. It is believed to be underlie by inherited genetic predispositions related to the genetic polymorphism of several enzymes involved in the detoxification and xenobiotic metabolism. In this review, we collect and discuss the evidence reported up to date on the association between lung cancer and genetic polymorphism of cytochromes P450, N-acetyltransferase, glutathione S-transferases, microsomal epoxide hydrolase, NAD(P)H:quinone oxidoreductase, myeloperoxidase and glutathione peroxidase. All these genes might appear to be candidates for lung cancer susceptibility genes, nevertheless, the present state of the art still offers only a limited explanation of the link between such polymorphisms and increased risk of lung cancer.

Discordance between N-acetyltransferase 2 phenotype and genotype in a population of Hmong subjects

Polymorphisms of N-acetyltransferase 2 (NAT2) acetylation may influence drug toxicities and efficacy and are associated with a differential susceptibility to select cancers. Acetylation phenotype may have clinical implications. The purposes of this study were to determine the genetic basis of an apparent predominance of slow acetylation phenotype and to assess concordance with genotype in a population of Hmong residing in Minnesota. Urine and DNA obtained from unrelated Hmong 18 to 65 years of age were used to determine phenotype from caffeine metabolites, whereas direct nucleotide sequencing of the NAT2 coding region, followed by cloning, identified all known allelic variants. From 61 subjects (27 men, 30 +/- 11 years), analysis of 50 urine-DNA pairs identified 46 (92%) slow acetylators and 4 (8%) rapid acetylators by phenotype. Genotypic analysis inferred 5 (10%) slow acetylators and 45 (90%) rapid acetylators. There is 86% discordance between phenotype and genotype. A predominance of NAT2 slow acetylation phenotype in the Hmong is confirmed, and a significant discordance between NAT2 phenotype and genotype is identified. In this population, slow acetylation phenotype determined by a metabolic probe would not have been predicted by genotype alone. Environmental, genetic, or phenotypic anomalies that may contribute to this discordance should be considered and evaluated in future studies within this unique population.

Effect of natural analogues of trans-resveratrol on cytochromes P4501A2 and 2E1 catalytic activities

The aim was to assess the inhibitory effect of a series of naturally occurring trans-resveratrol analogues on cytochromes P450, namely CYP1A2 and CYP2E1, in vitro in order to analyse any structure-activity relationships. 3,5-Dimethoxy-4'-hydroxy-trans-stilbene (pterostilbene), 3,4',5-trimethoxy-trans-stilbene (TMS), 3,4'-dihydroxy-5-methoxy-trans-stilbene (3,4'-DH-5-MS) and 3,5-dihydroxy-4'-methoxy-trans-stilbene (3,5-DH-4'-MS) inhibited the activity of CYP1A2, with K(i) = 0.39, 0.79, 0.94 and 1.04 microM, respectively. Piceatannol (3,3',4,5'-tetrahydroxy-trans-stilbene) was the least potent inhibitor of CYP1A2 with a K(i) = 9.67 microM. Piceatannol and TMS in the concentration range 1-100 microM did not inhibit CYP2E1 activity. The activity of this enzyme likewise was not significantly influenced by pterostilbene and 3,5-DH-4'-MS with IC(50) > 100 microM, whereas 3,4'-DH-5-MS appeared to be a moderately potent, competitive inhibitor of CYP2E1 (K(i) = 42.6 microM). Structure-activity relationship analysis leads to the conclusion that the substitution of hydroxy groups of resveratrol with methoxy groups increases the inhibition of CYP1A2, yet the number and position of methylation are not essential. However, the 4'-hydroxy group in trans-resveratrol and its analogues may play an important role in the interaction with a binding site of CYP2E1.

Metabolism of cytostatically active 6-aminobenzo[c]phenanthridines by human and porcine hepatic microsomes and recombinant cytochrome P450 enzymes

A new and convenient two-step synthesis of 11-substituted 6-amino-11,12-dihydrobenzo[c]phenanthridines and 6-aminobenzo[c]phenanthridines (BPs and BP-Ds) was developed recently in the authors' laboratory. These compounds revealed a high antitumoral activity in in vitro and in vivo test systems. In particular, 11-phenyl-substituted derivatives with two or three methoxy groups showed good activity. It was not clear if the dihydro-derivatives (BPs) were transformed enzymatically into the phenanthridines (BP-Ds), thus acting as prodrugs. The in vitro metabolism of several of these cytostatically active 6-aminobenzo[c]phenanthridines was investigated using human and porcine liver microsomes and a range of expressed human cytochrome P450 enzymes. High-performance liquid chromatography and liquid chromatography-mass spectrometry analysis were used for the quantification and structural identification of the observed metabolites. Aromatic hydroxylation was observed to be the major metabolic pathway in addition to a number of other metabolites. The formation of N-hydroxy- and 6-oxo-derivatives was detected only in very small amounts. BP derivatives are not prodrugs of BP-Ds and no significant differences between human and porcine microsomes were observed, confirming the pig as a good model for metabolism studies of these compounds.

Plasma/blood pharmacokinetics and metabolism after dermal exposure to para-aminophenol or para-phenylenediamine

The pharmacokinetics and metabolism following dermal application of [(14)C]-para-aminophenol (PAP) or [(14)C]-para-phenylenediamine (PPD) were investigated. Groups of rats were treated under occlusion for 24 h with 12.5 mg/kg [(14)C]-PAP, or for 4h with 50 mg/kg [(14)C]-PPD on 10% or 20% of their body surface area, respectively. A female minipig was also treated dermally (24 h, occlusion) with 4.7 mg/kg [(14)C]-PAP on 10% of its body surface area. Blood and plasma samples were analysed for radioactivity and presence of metabolites. In PAP-treated rats, mean plasma levels at 0.5, 1, 2, 4, 8 or 24h were 0.16, 0.24, 0.38, 0.50, 0.36 or 0.14 microg [(14)C]-PAP equivalents/ml, respectively. The plasma half-life was 5.95 h, the C(max) was 0.5 microg/ml, the t(max) was 4 h, and the AUC(0-infinity) was 9.27 microg-equivalentsh/ml. No free PAP was detected in the plasma, but 3 metabolites (M1, M2 and M3) were found in 2-, 4- or 8-h samples at ranges from 0% to 17.7% (M1), 27.6% to 45.0% (M2) or 46.9% to 70% (M3) of the total plasma radioactivity. M2 was identified as acetylated PAP (paracetamol, acetaminophen, APAP), whereas M1 and M3 were identified as O-glucuronide or O-sulfate conjugates of APAP, respectively. In the pig, very low levels of radioactivity (C(max) of approximately 10 ng/ml) were found in the blood, and identified as APAP. Analysis of plasma of PPD-treated rats at 4 h after topical treatment revealed levels of 1.41 +/- 0.34 microg/ml [(14)C]-PPD-equivalents in males, and 7.40 +/- 1.83 microg/ml in females. Radioactivity, reflected a single metabolite, which was identified to be N,N'-diacetylated PPD. Comparison of the plasma APAP levels in rats or the pig following topical PAP with corresponding human plasma levels after a single oral therapeutic dose of APAP suggested a substantial margin of safety. Overall, the results suggest that topically applied PAP or PPD are metabolised in the skin, presumably by N-acetyltransferase-1 resulting in systemic exposure to acetylated metabolites, and not to their parent arylamines.

The CYP1A2-164A→C polymorphism (CYP1A2*1F) is associated with the risk for colorectal adenomas in humans

Colorectal cancer (CRC) is believed to be related to the intake of processed meat and the formed heterocyclic aromatic amines (HCA) herein, which are metabolically activated by the enzymes cytochrome P4501A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). The influence of genotypic and phenotypic variations for CYP1A2 and NAT2 on the risk for colorectal adenomas was investigated in 94 individuals at different risk of developing CRC. Significant associations were found between the CYP1A2-164A-->C polymorphism (CYP1A2*1F) and the risk of colorectal adenomas, suggesting that the studied polymorphism plays an important role in CRC risk in humans.

Herbal interactions involving cytochrome p450 enzymes: a mini review

The metabolism of a drug can be altered by another drug or foreign chemical, and such interactions can often be clinically significant. Cytochrome P450 (CYP) enzymes, a superfamily of enzymes found mainly in the liver, are involved in the metabolism of a plethora of xenobiotics and have been shown to be involved in numerous interactions between drugs and food, herbs and other drugs. The observed induction and inhibition of CYP enzymes by natural products in the presence of a prescribed drug has (among other reasons) led to the general acceptance that natural therapies can have adverse effects, contrary to the popular beliefs in countries where there is an active practice of ethnomedicine. Herbal medicines such as St. John's wort, garlic, piperine, ginseng, and gingko, which are freely available over the counter, have given rise to serious clinical interactions when co-administered with prescription medicines. Such adversities have spurred various pre-clinical and in vitro investigations on a series of other herbal remedies, with their clinical relevance remaining to be established. Although the presence of numerous active ingredients in herbal medicines, foods and dietary supplements complicate experimentation, the observable interactions with CYP enzymes warrant systematic studies, so that metabolism-based interactions can be predicted and avoided more readily. This article highlights the involvement of CYP enzymes in metabolism-related drug-herb interactions and the importance of gaining a mechanism-based understanding to avoid potential adverse drug reactions, in addition to outlining other contributory factors, such as pharmacogenetics and recreational habits that may compound this important health issue.

Urinary mutagenicity, CYP1A2 and NAT2 activity in textile industry workers

The two major causes of bladder cancer have been recognised to be cigarette smoke and occupational exposure to arylamines. These compounds are present both in tobacco smoke and in the dyes used in textile production. Aromatic amines suffer oxidative metabolism via P450 cytochrome CYP1A2, and detoxification by the polymorphic NAT2. The aim of the present work was to assess the association between occupational-derived exposure to mutagens and CYP1A2 or NAT2 activity. This cross-sectional study included 117 textile workers exposed to dyes and 117 healthy controls. The urinary mutagenicity was determined in 24 h urine using TA98 Salmonella typhimurium strain with microsomal activation S9 (MIS9) or incubation with beta-glucuronidase (MIbeta). Urinary caffeine metabolite ratios: AFMU+1X+1U/17U, and AFMU/AFMU+1X+1U were calculated to assess CYP1A2 and NAT2 activities, respectively. The results show that workers present a strikingly higher urine mutagenicity than controls (p<0.0001), despite the implementation of the new restrictive norms forbidding the industrial use of the most carcinogenic arylamines. Neither NAT2 nor CYP1A2 activity had any effect on the markers of internal exposure to mutagens, since no significant differences were observed when the urinary mutagenicity of slow and fast acetylators (p>0.05) was compared, and the urinary mutagenicity was not significantly associated with the CYP1A2 activity marker (r=0.04 and r=-0.01 for MIS9 and MIbeta, respectively). This study clearly indicates the need for further protective policies to minimise exposure to the lowest feasible limit in order to avoid unnecessary risks.

N-acetyltransferase 2 polymorphisms in patients with Behcet's disease

It is possible that dietary, environmental factors and/or genetic polymorphisms in xenobiotic-metabolizing enzymes may contribute to the development of Behcet's disease. As N-acetyltransferase (NAT) 2 is an important xenobiotic-metabolizing enzyme and theoretically the nonacetylated xenobiotics may induce an autoimmune mechanism, the aim of the present study was to investigate whether the genetic polymorphism of NAT2 plays a role in susceptibility to Behcet's disease. Forty Behcet's disease patients and 82 control subjects were enrolled in the study. NAT2*5A, NAT2*6A, NAT27*A/B and NAT2*14A polymorphisms were detected by using real time PCR with LightCycler (Roche Diagnostics GmbH, Mannheim, Germany). The NAT2*5A and NAT2*6A mutant genotypes carried an increased risk of developing Behcet's disease [odds ratio (OR) = 66.29, 95% confidence interval (CI) = 8.21-535.33; and OR = 24; 95% CI = 2.04-304.98, respectively]. The NAT2*7A/B and NAT2*14A gene polymorphisms were not an increased risk for developing Behcet's disease. As a result of this study we conclude the NAT2 slow acetylator status may be a determinant in susceptibility to Behcet's disease. This finding may have implications for the theories of the pathogenesis of the disease as well as for therapeutic aspects.

Cancer and Molecular Biomarkers of Phase 2

Associations between genotypes of phase 2 enzymes and cancer risk are extracted from epidemiological studies, namely case-control studies. Variant alleles in glutathione S-transferase (GST), UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), and N-acetyltransferase (NAT) have been used as molecular genetic biomarkers of risk. GSTM(my)1 has been associated with an increased risk of colorectal cancer, lung cancer, and bladder cancer and GSTP(pi)1 with prostate cancer. UGT1A1*28 and *37 are both associated with an increased risk of breast cancer as is SULT1A1*2. The presence of UGT1A1*28 results in an increased risk of ovarian cancer and NAT2 of colorectal and lung cancer. A high frequency of SULT1A1*1 has been identified in patients with breast cancer; the role in colorectal cancer is more controversial. This chapter discusses the balance between carcinogen activation and detoxification in relation to phase 2 enzymes.

Single-track sequencing for genotyping of multiple SNPs in the N-acetyltransferase 1 (NAT1) gene

Background

Fast, cheap and reliable methods are needed to identify large populations, which may be at risk in relation to environmental exposure. Polymorphisms in NAT1 (N-acetyl transferase) may be suitable markers to identify individuals at risk.

Results

A strategy allowing to address simultaneously 24 various genetic variants in the NAT1 gene using the single sequencing reaction method on the same PCR product is described. A modified automated DNA sequencing using only one of the sequence terminators was used to genotype PCR products in single-track sequencing reactions of NAT1 and was shown to be universal for both DNA sequencing using labeled primers and labeled nucleotides. By this method we detected known SNPs at site T640G, which confers the NAT1*11 allele with frequency of 0.036, further T1088A and C1095A with frequency of 0.172 and 0.188, respectively and a deletion of TAATAATAA in the poly A signal area with a frequency 0.031. All observed frequencies were in Hardy Weinberg equilibrium and comparable to those in Caucasian population. The single-track signatures of the variant genotypes were verified on samples previously genotyped by RLFP.

Conclusions

The method could be of great help to scientists in the field of molecular epidemiology of screening of large populations for known informative biomarkers of susceptibility, such as NAT1.

Enhanced expression of human cytochrome P450 1A2 by co-expression with human molecular chaperone Hsp70

Cytochrome P450 (CYP) 1A2 is of great interest because of its important roles in the oxidation of numerous drugs and carcinogens. Hsp70, a molecular chaperone in human, is known to assist the correct folding of unfolded proteins. To achieve high yield of recombinant human CYP1A2 in Escherichia coli, the CYP1A2 encoding gene was co-expressed with the chaperone Hsp70 under the control of an inducible tac promoter in bicistronic format. Expression level of CYP1A2 in the bicistronic construct reached up to 410 nmol (lculture)(-1) within 16 h at 37 degrees C, which is approximately 2.7-fold increase compared to the expression yield of CYP1A2 alone without Hsp70. The present over-expression system may be useful for rapid production of large amounts of active CYP1A2 in E. coli.

MPO and SOD2 polymorphisms, gender, and the risk of non-small cell lung carcinoma

Manganese superoxide dismutase (SOD2) and myeloperoxidase (MPO) are polymorphic enzymes involved in reactive oxidative species metabolism. In this case-control study (830 non-small cell lung carcinoma (NSCLC) patients; 1119 controls) we evaluated whether the MPO -G463A polymorphism (associated with a novel estrogen receptor binding site) modifies the association between the SOD2 Ala16Val polymorphism and NSCLC risk differently by gender. For women carrying the MPO variant genotypes, the adjusted odds ratio of the SOD2 polymorphism (Val/Val vs. Ala/Ala) was 3.26 (95% CI, 1.55-6.83). No associations were found in men or in women carrying the MPO GG wildtype genotype.

High-level expression of human cytochrome P450 1A2 by co-expression with human molecular chaperone HDJ-1(Hsp40)

Human cytochrome P450 (CYP) 1A2 is of great interest because of its important roles in the oxidation of numerous drugs and carcinogens. HDJ-1, a molecular chaperone in human, is known to assist the correct folding of unfolded proteins. To achieve high yield of recombinant human CYP1A2 in Escherichia coli, the CYP1A2 encoding gene was co-expressed with the chaperone HDJ-1 under the control of an inducible tac promoter in bicistronic format. Expression level of CYP1A2 in the bicistronic construct reached up to 520 nmol/liter culture within 16 h at 37 degrees C, which is 3.4-fold increase compared to the expression yield of CYP1A2 alone without HDJ-1. By co-expression with HDJ-1, the catalytic activity of CYP1A2 was also increased 5.5-fold. The activity increase seems to be associated with the increase of CYP production at whole cell level. The present over-expression system may be useful for rapid production of large amounts of active human CYP1A2 in E. coli.

Relation between bladder cancer and protein oxidation

DNA, protein oxidation and lipid peroxidation possess a major impact in carcinogenesis. Also, inflammatory and oxidative events have remarkable importance in bladder cancer. Thus, in this study total protein, protein carbonyl, nitrotyrosine, thiol residues, non-protein thiols, lipid peroxidation, and also, because of their relations to the above parameters, iron and iron binding levels have been investigated in patients with bladder cancer and in control group. Statistical evaluation of the results demonstrated significantly lower plasma protein levels in the patients with bladder cancer, as compared to the healthy control group. Serum iron levels in patients with invasive bladder cancer were found to be significantly lower when compared with non-invasive group. Protein carbonyl groups were remarkably higher in bladder cancer patients than in healthy controls. Patients with bladder cancer were demonstrated to have significantly lower levels of total thiol groups and protein-bound thiol groups as compared to healthy controls. Protein-bound thiol groups in patients with invasive bladder cancer revealed a more significant decline, than in non-invasive group.

CYP1A2 and NAT2 genotype/phenotype relations and urinary excretion of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in a human dietary intervention study

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mutagenic and carcinogenic heterocyclic amine formed during ordinary cooking, and is subsequently metabolically activated by cytochrome P4501A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). Respective genes encoding for these enzymes, display polymorphic distribution in the human population and are thus believed to cause interindividual differences in cancer risk susceptibility. The present study investigated the influence of dietary exposure and CYP1A2 and NAT2 genotypes and phenotypes on differential urinary PhIP excretion levels in 71 human volunteers after consumption of either a high (7.4 ng/g) or low (1.7 ng/g) dose of PhIP. Urinary PhIP excretion levels were found to reflect recent dietary exposure levels, with average levels of 174% (high dose group) and 127% (low dose group), as compared to pre-feed levels. Urinary caffeine metabolite ratios were significantly different between the two NAT2 genotypes, whereas for CYP1A2, the apparent difference in metabolic ratios between the genotypes was statistically non-significant. Significant correlations were firstly found between the CYP1A2-164A-->C (CYP1A2*1F) polymorphism and differential urinary PhIP excretion levels. Although the found correlations are driven primarily by a small number of subjects possessing the homozygous variant constellation, the strong influence of this genotype indicates that the CYP1A2*1F polymorphism could play an important role in human cancer risk susceptibility.

Using Hierarchical Modeling in Genetic Association Studies with Multiple Markers: Application to a Case-Control Study of Bladder Cancer

Background: Genetic association studies are generating much information, usually in the form of single nucleotide polymorphisms in candidate genes. Analyzing such data is challenging, and raises issues of multiple comparisons and potential false-positive associations. Using data from a case-control study of bladder cancer, we showed how to use hierarchical modeling in genetic epidemiologic studies with multiple markers to control overestimation of effects and potential false-positive associations. Methods: The data were first analyzed with the conventional approach of estimating each main effect individually. We subsequently employed hierarchical modeling by adding a second stage (prior) model that incorporated information on the potential function of the genes. We used an empirical-Bayes approach, estimating the residual effects of the genes from the data. When the residual effect was set to zero, we instead used a semi-Bayes approach, in which they were pre-specified. We also explored the impact of using different second-stage design matrices. Finally, we used two approaches for assessing gene-environment interactions. The first approach added product terms into the first-stage model. The second approach used three indicators for subjects exposed to gene-only, environment-only, and both genetic and environmental factors. Results: By pre-specifying the prior second-stage covariates, the estimates were shrunk to the mean of each pathway. The conventional model detected a number of positive associations, which were reduced with the hierarchical model. For example, the odds ratio for myeloperoxidase (G/G, G/A) genotype changed from 3.17 [95% confidence interval (CI), 1.32-7.59] to 1.64 (95% CI, 0.81-3.34). A similar phenomenon was observed for the gene-environment interactions. The odds ratio for the gene-environment interaction between tobacco smoking and N-acetyltransferase 1 fast genotype was 2.74 (95% CI, 0.68-11.0) from the conventional analysis and 1.24 (95% CI, 0.80-1.93) from the hierarchical model. Conclusion: Adding a second-stage hierarchical modeling can reduce the likelihood of false positive via shrinkage toward the prior mean, improve the risk estimation by increasing the precision, and, therefore, represents an alternative to conventional methods for genetic association studies.

Cytochrome P450 1A2 (CYP1A2) activity, mammographic density, and oxidative stress: a cross-sectional study

Introduction

Mammographically dense breast tissue is a strong predictor of breast cancer risk, and is influenced by both mitogens and mutagens. One enzyme that is able to affect both the mitogenic and mutagenic characteristics of estrogens is cytochrome P450 1A2 (CYP1A2), which is principally responsible for the metabolism of 17β-estradiol.

Methods

In a cross-sectional study of 146 premenopausal and 149 postmenopausal women, we examined the relationships between CYP1A2 activity, malondialdehyde (MDA) levels, and mammographic density. In vivo CYP1A2 activity was assessed by measuring caffeine metabolites in urine. Levels of serum and urinary MDA, and MDA–deoxyguanosine adducts in DNA were measured. Mammograms were digitized and measured using a computer-assisted method.

Results

CYP1A2 activity in postmenopausal women, but not in premenopausal women, was positively associated with mammographic density, suggesting that increased CYP1A2 activity after the menopause is a risk factor for breast cancer. In premenopausal women, but not in postmenopausal women, CYP1A2 activity was positively associated with serum and urinary MDA levels; there was also some evidence that CYP1A2 activity was more positively associated with percentage breast density when MDA levels were high, and more negatively associated with percentage breast density when MDA levels were low.

Conclusion

These findings provide further evidence that variation in the activity level of enzymes involved in estrogen metabolism is related to levels of mammographic density and potentially to breast cancer risk.

Molecular epidemiology of colon cancer

Colorectal cancer appears to have rapidly increased over the past two decades in Korea. Environmental factors, characterized by a western life style, seem to be closely related to the increased risk of colorectal cancer. Higher intakes of meat, a lower vegetable intake, a lack of physical activity, obesity, and alcohol drinking have been suggested to be risk factors for colorectal cancer in the numerous epidemiologic studies. Several specific associations have also been observed between genetic polymorphisms and colorectal cancer. Moreover, it has been postulated that environmental factors and a genetic predisposition work in concert in colorectal cancer development. A stronger association between red meat intake and colorectal cancer among those with rapid acetylators at either the NAT1 or NAT2 locus was reported, particularly for colorectal cancer associated with K-ras mutations. The protective effect of the homozygous variant TT form of the MTHFR genotype on the risk of colon cancer seems to be modified by the level of methyl diets, i.e., by folate, which has a protective effect, or conversely by alcohol. The insulin-related pathway, which possibly explains at a mechanistic level the effect of physical activity and obesity on colon cancer, appears to be a common denominator in colon cancer and in other metabolic disorders, such as diabetes mellitus and dyslipidemia. Hyperinsulinemia has been proposed as an explanation for the association between a Western lifestyle and colon cancer risk. Further studies, that incorporate both genetic and environmental factors, are needed to fully explain and identify the underlying pathway of colorectal carcinogenesis.