Polymorphism in CYP1A1 and CYP2E1 genes and susceptibility to leukoplakia in Indian tobacco users

Inter-individual genetic differences may contribute to differences in susceptibility to human diseases triggered by environmental exposures. In this study, we investigated polymorphisms at two sites in the CYP1A1 and three sites in the CYP2E1 genes in 99 leukoplakia patients and 227 controls from one Indian population. The frequencies of genotypes at these polymorphic sites (MspI and Ileu/Val) in the CYP1A1 and (PstI, RsaI and DraI) in the CYP2E1 genes, were similar in patient and control groups. But the combined rare and heterozygous genotypes (CC+CD) at the DraI site in the CYP2E1 gene were over-represented among patients compared with controls (age-adjusted odds ratio (OR)=2.02, 95% confidence interval (CI)=1.21–3.35). Light tobacco smokers (i.e. <21 pack-year) and light tobacco chewers (i.e. <104 chewing-year) with a “rare” C allele at the DraI site had high risk of leukoplakia (OR=2.88, 95% CI=1.16–7.22; OR=2.94, 95% CI=1.15–7.65, respectively). The “mixed tobacco” users with “rare” C allele are more susceptible to the disease than “exclusive” tobacco smokers and chewers. The results indicate that the “rare” C allele at the DraI polymorphic site in CYP2E1 gene may enhance susceptibility to leukoplakia among tobacco users in this population. But the low sample size limited the power to precisely estimate the tobacco–genotype interactions.