BACKGROUND: Molecular epidemiological studies have now provided evidence that an individual susceptibility to cancer is mediated by genetic and environmental factors. Genetic polymorphisms have been described for enzymes involved in the metabolism of tobacco carcinogens and cancer risk is determined by the degree of expression and/or activity of enzymes involved in carcinogen activation or deactivation. The objective of this study was to investigate the GSTM1 null polymorphism and the risk for oral leukoplakia in individuals with tobacco-smoking habit in a Brazilian population. METHODS: A total of 52 tobacco-smoking patients with oral leukoplakia and 52 tobacco-smoking controls were recruited in a Brazilian population. The GSTM1 genotypes were studied by polymerase chain reaction-based methods. RESULTS: The frequency of the GSTM1 null genotype in the group with oral leukoplakia (57.7%) was statistically different from the controls (34.6%; OR: 2.57, 95% CI: 1.16-5.69, P < 0.05). The stratification of the samples according to the level of dysplasia showed increased prevalence of GSTM1 null genotype on lesions with moderate/severe histological dysplasia (68.2%) compared with the control group (31.9%). This difference was statistically significant (OR: 4.59, 95% CI: 1.29-16.33, P < 0.05). CONCLUSION: In conclusion, the GSTM1 null genotype may increase the risk for oral leukoplakia development.

The cytogenetic effects of cigarette smoke has been evaluated as one of many potential confounders in a large number of biomonitoring studies of occupationally or environmentally exposed populations and control subjects. Despite the well-known presence of carcinogens in the cigarette smoke, the results in the scientific literature linking smoking habits to micronuclei (MN) frequency, one of the cytogenetic markers, are rather controversial. Here, we investigated the relationships among MN frequency, smoking habits and five folate metabolic enzyme gene polymorphisms (MTHFR C677T and A1298C, MTR A2756G, MTRR A66G and TYMS 3'UTR) in 132 healthy Japanese men who were non-habitual drinkers. In never- and former-smokers, no statistically significant differences in the mean MN frequencies were observed according to the five folate metabolic enzyme gene polymorphisms. In current-smokers, however, subjects with the AA genotype for MTRR had a significantly higher mean MN frequency than the AG genotypes for MTRR (p<0.05). Furthermore, among subjects with the AA genotype for MTRR, current-smokers were found to have a significantly higher mean MN frequency than never- and former-smokers (p<0.05). To further characterize this association, we stratified the smoking status into five groups: non-smokers (never-smokers and former-smokers), 1-10 cigarettes/day, 11-20 cigarettes/day, 21-30 cigarettes/day and >or=31 cigarettes/day. There was an overall trend for the mean MN frequency in subjects with the MTRR AA genotype to increase as the number of cigarettes smoked per day increased (p<0.01, Jonckheere-Terpstra test). The results of our preliminary study suggest that the MTRR AA genotype acts to increase the MN frequency resulting from cigarette smoking. Therefore, studies on human genotoxicity based on cytogenetic markers of MN should take into account both the MTRR polymorphism and the potential confounding effect of smoking, although these preliminary findings need to be validated in larger populations because of the relatively small sample size.

Some aromatic amines are considered to be putative bladder carcinogens. Hemoglobin (Hb) adducts of 3-aminobiphenyl (3-ABP) and 4-aminobiphenyl (4-ABP) have been used as biomarkers of exposure to aromatic amines from cigarette smoke. One of the goals of this study was to determine intra- and inter-individual variability in 3-ABP and 4-ABP Hb adducts and to explore the predictability of ABP Hb adduct levels based on caffeine phenotyping. The study was conducted in adult smokers (S, n = 65) and non-smokers (NS, n = 65). The subjects were phenotyped for CYP1A2 and NAT2 using urinary caffeine metabolites. Blood samples were collected twice within 6 weeks and adducts measured by GC/MS. The levels of 4-ABP Hb adducts were significantly (p < 0.0001) greater in S (34.5 +/- 21.06 pg/g Hb) compared to NS (6.3 +/- 3.02 pg/g Hb). The levels of 3-ABP Hb adducts were below the limit of quantification (BLOQ) in most (82%) of the NS and about 10-fold lower in S (3.6 +/- 3.29 pg/g Hb) compared to 4-ABP Hb adducts. No differences were observed in the adduct levels between weeks 1 and 6 in the smokers, suggesting that a single sample would be adequate to monitor cigarette smoke exposure. The regression model developed with CYP1A2, NAT2 phenotype and number of cigarettes smoked (NCIG) accounted for 47% of the variability in 3-ABP adducts, whereas 32% variability in 4-ABP adducts was accounted by CYP1A2 and NCIG. The ratio of 4-ABP Hb adducts in adult S:NS was approximately 5:1, whereas 3-ABP Hb adducts levels were BLOQ in some S, exhibited large interindividual variability ( approximately 91% compared to 57% for 4-ABP Hb) and poor dose response relationship. Therefore, 4-ABP Hb adduct levels may be a more useful biomarker of aminobiphenyl exposure from cigarette smoke.

BACKGROUND: Exposure to environmental carcinogens leads to oral squamous cell carcinoma (OSCC); however, the impact of genetic variations in carcinogen metabolisms and DNA repair on OSCC risk considering environmental exposures has not been clearly elucidated. METHODS: We conducted a case-control study with 122 cases and 241 controls. The risk of OSCC was evaluated in 10 genetic polymorphisms of nine genes, such as CYP1A1, CYP2E1, GSTM1, GSTT1, XPA, XPC, XPC, XPF and ERCC1. Gene-environment interaction was also evaluated. RESULTS: We found that CYP2E1 and XPA polymorphisms significantly affected the OSCC risk. Gene-environment interactions with smoking were significant for CYP2E1 and ERCC1 polymorphisms. Odds ratios for gene-environment interaction were 7.98 (P = 0.036), 9.67 (P = 0.017) and 8.49 (P = 0.031) for CYP2E1RsaI, DraI and ERCC1 polymorphisms, respectively. No interaction was observed with heavy drinking and any polymorphisms. CONCLUSION: CYP2E1, XPA and ERCC1 polymorphisms may affect the risk of OSCC.

BACKGROUND: Variation in the glutathione S-transferase (GSTP1) gene and occupational polycyclic aromatic hydrocarbons (PAH) exposure are putative prostate cancer risk factors. An Ile/Val polymorphism in codon 105 of GSTP1 affects its enzymatic activity toward PAH detoxification, a possible mechanism in prostate carcinogenesis. METHODS: To determine whether the GSTP1 Ile105Val polymorphism modifies prostate cancer risk associated with occupational PAH exposure, we studied 637 prostate cancer cases and 244 controls of White and African-American race from the Henry Ford Health System in Detroit, Michigan. Occupational exposure to PAH from wood, petroleum, coal or other sources through respiratory and cutaneous routes was retrospectively assessed by expert review of job histories. The association of occupational PAH exposure and GSTP1 Ile105Val polymorphism with prostate cancer was tested in multiple logistic regression models adjusting for potential confounders. Cases were over sampled compared with controls to evaluate gene-environment interaction with the statistically efficient case-only analytic approach. RESULTS: Neither carriage of the GSTP1 Val(105) variant allele nor occupational PAH exposure was significantly associated with prostate cancer. However, case-only analyses revealed that carriage of the GSTP1 Val(105) variant allele was associated with increasing levels of occupational respiratory PAH exposures from any source and from petroleum (trend test p=0.01 for both). The GSTP1 Val(105) allele was observed most frequently in cases in the highest quartile of occupational respiratory PAH exposures from petroleum (OR=1.74; 95% CI=1.11-2.72) or from any source (OR=1.85; 95% CI=1.19-2.89). The gene-environment risk estimate in the highest PAH petroleum exposure quartile was greatest in men under age 60 (OR=4.52; 95% CI=1.96-10.41) or with a positive family history of prostate cancer (OR=3.02; 95% CI=1.15-7.92). CONCLUSIONS: Our results suggest men who carry the GSTP1 Val(105) variant and are exposed at high levels to occupational PAH have increased risk for prostate cancer. This increased risk is more pronounced in men under age 60 or with a family history of prostate cancer.

The cytochrome P4501A1 (CYP1A1) is involved in the metabolism of environmental carcinogens and estrogen. We hypothesized that CYP1A1 genetic polymorphism may be a susceptibility factor for endometrial hyperplasia (EH) and endometrial carcinoma (ECa). We therefore evaluated this hypothesis in patients with EH and ECa and control subjects using allele-specific polymerase chain reaction-based method in a Turkish population. The patients with CYP1A1 Ile/Val genotype had a fivefold higher risk of having EH than those with Ile/Ile. In contrast, a higher frequency of any Val genotype (Ile/Val and Val/Val) was found in patients with EH, indicating that persons carrying any Val allele are at increased risk for developing EH. In the ECa group, patients were also more likely to have CYP1A1 Ile/Val allele, with an adjusted odds ratio of 3.0. Moreover, there was a statistically significant increase in relative risk association with any Val genotype between patients and controls, suggesting that individuals carrying any Val genotype are at increased risk for developing ECa. We concluded that variant alleles of the CYP1A1 gene might be associated with EH and ECa susceptibility. Further studies with a large sample size should be considered to address issues of interactions between CYP1A1 and other risk factors.