Impact of xenobiotic-metabolizing gene polymorphisms on breast cancer risk in South Indian women

Background Functional variants of the xenobiotic-metabolizing genes (XMG) might modulate breast cancer (BC) risk by altering the rate of metabolism and clearance of myriad types of potent carcinogens from the breast tissue. Despite mounting evidence on the role of XMG variants on BC risk, the current knowledge regarding their influence on BC development is still fragmentary. Methods The present study examined the candidate genetic variants in CYP1A1 , NQO1 , GST-T1 , GST-M1, and GST-P1 in 1002 subjects (502 BC patients and 500 disease-free women). PCR–RFLP was employed to genotype the mono-nucleotide variation in CYP1A1 , NQO1 , and GST-P1, and allele-specific PCR was used to detect the deletion polymorphism in GST - T1 and GST-M1 genes. Results Regarding CYP1A1-M1 polymorphism, the heterozygous TC and mutant CC genotype conferred 1.47-fold (95% CI 1.13–1.91, p = 0.004) and 1.84-fold (95% CI 1.17–2.91, p = 0.009) elevated risk of BC. GST-T1 null genotype was associated with increased BC risk (OR 1.47; 95% CI 1.02–2.11, p = 0.037). For the NQO1 C609T variant, the mutant T allele was associated with BC risk with an odds ratio of 1.22 (95% CI 1.02–1.48, p = 0.034). Combinatorial analysis indicated that the presence of NQO1*2 (CT), CYP1A1-M1 (CC), and GST-P1 rs1695 (AG) genotypes conferred 16.7-fold elevated risk of BC (95% CI 3.65–76.85; p < 0.001). Moreover, GST-M1 null genotype was associated with the development of larger primary breast tumors. Conclusion Xenobiotic-metabolizing gene polymorphisms may play a crucial role in mammary carcinogenesis in South Indian women.