Interaction between polymorphisms of DNA repair genes significantly modulated bladder cancer risk

DNA repair is a primary defense mechanism against damage caused by exogenous and endogenous sources. We examined the associations between bladder cancer and 7 polymorphisms from 5 genes involved in the maintenance of genetic stability (MMR: MLH1-93G>A; BER: XRCC1--77T>C and Arg399Gln; NER:XPC Lys939Gln and PAT +/-; DSBR:ATM G5557A and XRCC7 G6721T) in 302 incident bladder cancer cases and 311 hospital controls. Genotyping was done using a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique. The homozygous variant of XRCC7 G6721T (Odds Ratio [OR]: 2.36; 95% Confidence Interval [CI]: 1.13-4.92) was associated with increased bladder cancer risk. In an analysis of combined genotypes, the combination of XRCC1Arg399Gln (Gln allele) with XRCC1-77 T/T led to an increase in risk (OR: 1.61; 95% CI: 1.10-2.36). Moreover, when the XPCLys939Gln (Gln allele) (nucleotide excision repair [NER]) was present together with XRCC7 (T allele) (double strand break repair [DSBR]), the bladder cancer risk dramatically increased (OR: 4.42; 95% CI: 1.23-15.87). Our results suggest that there are multigenic variations in the DNA repair pathway involved in bladder cancer susceptibility, despite the existence of ethnic group differences.