Polymorphisms at GSTM1 and GSTT1 gene loci and susceptibility to cervical cancer in Indian population

Multiple allelism at loci encoding detoxifying enzymes is associated with cancer risk. Glutathione S-transferase (GSTs) catalyzes the conjugation of glutathione to numerous potentially genotoxic compounds. This study evaluates the influence of genetic polymorphisms of GST M1 and GST T1 on susceptibility to cervical cancer. A multiplex polymerase chain reaction method was used to detect the presence or absence of the GSTM1 and GSTT1 genes in genomic DNA isolated from cases with cervical cancer (n=142) and normal controls (n=96). The results showed that the frequency of homozygous GSTM1 null genotype was higher in cervical cancer cases (57.0%) as compared to controls (34.4%) and the differences were significant (p<0.05), OR=2.5, 95% CI: 1.4--4.5. The frequency of homozygous GSTT1 null genotype in cancer cases was 19.7% in comparison to 12.5% in controls, however, the difference was not statistically significant (OR=1.7, 95% CI: 0.8-3.8). Significant difference was found between the cases and controls in the distribution of the null genotype of GST M1 in individuals aged above 45 years (p=0.04), but this difference was not significant in individuals aged below 45 years (p=0.06). No significant differences were found in cervical cancer cases and controls when data were analyzed according to age group for GSTT1 null genotype. Further, the combined analysis of both GSTM1 null and GSTT1 null genotypes did not appear to influence the susceptibility to cervical cancer, suggesting that polymorphisms of other detoxifying enzymes may play a significant role in cervical carcinogenesis.