DNA repair gene XRCC3 polymorphisms and bladder cancer risk: a meta-analysis

The X-ray repair cross-complementing group 3 (XRCC3) in homologous recombination repair (HRR) pathway plays a vital role in DNA double-strand break repair (DSBR). Variants in the XRCC3 gene might result in altered protein structure or function which may influence DSBR efficiency and lead to cancer. Numerous epidemiological studies have been conducted to evaluate the association between XRCC3 polymorphisms and bladder cancer risk. However, the results of these previous studies have been inconsistent. To derive a more precise estimation of the association, we performed a meta-analysis of all available studies relating XRCC3 polymorphisms and bladder cancer. All studies published up to April 2013 on the association between XRCC3 polymorphisms and bladder cancer risk were identified by searching electronic databases PubMed, EMBASE, and Chinese Biomedical Literature databases. The association between the XRCC3 polymorphisms and bladder cancer risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs). A total of 16 case-control studies met the inclusion criteria and were selected. With respect to C18067T polymorphism, significant increased bladder cancer risk was found when all eligible studies were pooled into the meta-analysis (TT vs. CC: OR = 1.174, 95%CI = 1.033-1.335, P = 0.014 and recessive model TT vs. TC + CC: OR = 1.147, 95%CI = 1.020-1.290, P = 0.022, respectively). The results were still significant after excluding the Hardy-Weinberg equilibrium violation studies (TT vs. CC: OR = 1.178, 95%CI = 1.036-1.339, P = 0.013 and recessive model TT vs. TC + CC: OR = 1.144, 95%CI = 1.017-1.287, P = 0.025, respectively). In subgroup analysis by ethnicity, significant elevated risk was found among Asians (dominant model TT + TC vs. CC: OR = 1.285, 95%CI = 1.012-1.631). In the subgroup analyses according to smoking status, no significant association was detected in all genetic comparison models. With respect to A17893G and A4541G polymorphisms, no significant association with bladder cancer risk was observed in the overall and subgroup analyses. This meta-analysis suggests that the XRCC3 C18067T polymorphism was associated with increased bladder cancer risk especially among Asians. However, the XRCC3 A17893G and A4541G polymorphisms may not play important roles in bladder carcinogenesis. Further studies with larger sample sizes are needed to validate our finds.