Purpose: Genetic polymorphisms in DNA repair genes may influence variations in individual DNA repair capacity, which could be associated with the development of cancer. We detected the distributions of three single-nucleotide polymorphisms (XRCC1 Arg399Gln, XRCC3 Thr241Met and XPD Lys751Gln) in DNA repair genes, and assessed the associations of these genetic polymorphisms with colon and rectal cancer susceptibility as well as evaluated the interactions of gene-gene and gene-environment in a case-control study of an Indian population.
Methods: This case-control study was conducted with 302 cases (including 59 colon and 243 rectal cancer patients) and 291 cancer-free healthy controls. Genotypes were determined by PCR-RLFP assays. The effects [odds ratios (ORs) and 95% confidence intervals (95% CIs)] of genetic polymorphisms on colorectal cancer were estimated using unconditional logistic regression.
Results: The XRCC1 399Gln allele was found to be associated with a significantly increased rectal cancer risk among men (OR = 1.65, 95% CI 1.04-2.64). Whereas the XRCC3 241Met allele showed a protective tendency against rectal cancer (OR = 0.68, 95% CI 0.46-1.02) for both men and women. Furthermore, a combination of the XRCC1 399Gln allele with XRCC3 Thr/Thr genotype and the XPD 751Gln allele demonstrated the highest rectal cancer risk (OR = 3.52, 95% CI 1.43-9.44).
Conclusions: The combined effects of putative risk alleles/genotypes for different DNA repair pathways may strengthen the susceptibility to rectal cancer.