Homozygous Null Genotype at Glutathione S-transferase M1 Locus as a Risk Factor for Oral Squamous Cell Carcinoma in Indian Tobacco Users

Abstract

KEYWORDS Indian population; tobacco smoking/chewing; oral SCC; GSTM1; GSTT1; CYP1A1; CYP2E1; genetic polymorphism ABSTRACT Inter-individual differences in sensitivity to chemical carcinogens may contribute to differences in susceptibility to human cancer subsequent to environmental exposures. It has been reported that polymorphisms in glutathione S-transferase (GST) and cytochrome P-450 oxidase (CYP) genes are associated with increased risk of tobacco-related cancers in different ethnic populations. In this study, we investigated polymorphisms in GSTM1, GSTT1, CYP1A1 and CYP2E1 genes in 80 oral squamous cell carcinoma (SCC) patients and 67 controls from one Indian population. Prevalence of the GSTM1 homozygous null genotype was 39 in 80 patients (49%) compared to 18 in 67 controls (27%) (age and sex adjusted OR=1.8, 95% CI=1.0-3.6). Analyses of data on polymorphisms in GSTT1, CYP1A1 and CYP2E1 did not reveal significant differences in distribution of genotypes between patient and control groups. Our results confirm that GSTM1 homozygous null genotype adds to the risk of oral cancer development among tobacco users. But low sample size limited the power to estimate tobacco dose-genotype interactions.