Genetic polymorphisms of cytochrome P450CYP1A1 (*2A) and microsomal epoxide hydrolase gene, interactions with tobacco-users, and susceptibility to bladder cancer: a study from North India

The role of low penetrance genes and environmental factors in the etiology of bladder cancer (CaB) is unclear, but may involve genetic and environmental factors. Most environmental pro-carcinogens require metabolic activation by phase I enzymes (CYP450s), However, phase II enzyme (i.e., microsomal epoxide hydrolase: mEH) is mainly involved in the detoxification of wide variety of endogenous or exogenous carcinogens. Genetic differences in CYP1A1 gene and the mEH gene polymorphisms have been reported to be associated with susceptibility to various cancers. In our case-control study, we assess whether Msp1 polymorphism of CYP1A1 (CYP1A1*2A), and His(113) in exon 3 and Arg(139) in exon 4 of the mEH susceptibility genotypes, tobacco-use and age factors contribute to bladder cancer risk among Indians. A case-control study was conducted in 106 bladder cancer (CaB) patients and 160 age matched controls from similar ethnic background. The CYP1A1*2A and mEH genotypes were determined by polymerase chain reaction/restriction fragment length polymorphism method from DNA extracted from peripheral blood samples. Binary logistic regression model was used for assessing differences in genotype prevalence between patients and the controls. The Arlequin software package was used to compute haplotype frequencies. We observed non-significant association in T/C polymorphism of the CYP1A1 gene (CYP1A1*2A); however, the exon 3 His genotype of the mEH gene polymorphism alone (odds ratio = 2.67, P = 0.001) or in combination with tobacco-users were significantly associated with the risk of bladder cancer. No associations were observed with stage or grade of bladder tumor with these genotypes. In conclusion, our study demonstrated that exon 3 His genotype of the mEH are more prone to the risk of sporadic bladder cancer in North India.