Association between X-ray repair cross-complementing group 1(XRCC1) Arg399Gln polymorphism and endometriosis: A systematic review and meta-analysis

OBJECTIVE(S): X-ray repair cross-complementing group 1(XRCC1) gene is one of the DNA repair pathway genes playing a vital role in endometriosis risk. Various studies have explored the association between them, however, the results remained inconsistent. So to confirm the association between XRCC1 Arg399Gln polymorphism and the risk of endometriosis, a meta-analysis was conducted. STUDY DESIGN: PubMed, Web of Science, Science Director, Cochrane Library, Google Scholar, China National Knowledge Infrastructure (CNKI) and Wanfang Data databases were searched to identify the all relevant studies before Sep. 30, 2016 focusing on the association between XRCC1 Arg399Gln polymorphism and the risk of endometriosis. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated and analyzed by Review Manager 5.2 and Stata 12 to assess the strength of the association. Meanwhile, Begg's test was used to check the publication bias. RESULTS: The present meta-analysis identified 6 studies with 646 cases and 616 controls. The overall analysis revealed that the AA genotype exhibited a significant association with a decreased risk for endometriosis compared with GG (OR=0.43, 95%CI=0.20-0.94, P=0.03), GA (OR=0.57, 95%CI=0.35-0.95, P=0.03) and GG+GA (OR=0.54, 95%CI=0.31-0.96, P=0.04) respectively. In addition, subgroup analyses based on varied regions indicated that a total comparisons of allelic and various genetic models had statistical significances among Asians (A allele vs. G allele: OR=0.62, 95%CI=0.48-0.81, P=0.0004; AA vs. GG: OR=0.22, 95%CI=0.11-0.46, P<0.0001; AA vs. GA: OR=0.32, 95%CI=0.16-0.63, P=0.001; AA vs. GG+GA: OR=0.28, 95%CI=0.14-0.54, P=0.0002; AA+GA vs. GG: OR=0.28, 95%CI=0.14-0.54, P=0.008) but not among Middle Eastern. The Begg's test did not reveal any obvious publication bias in the present study. CONCLUSION(S): Our meta-analysis suggested that Arg399Gln in XRCC1 was associated with endometriosis risk. And especially in Asians, the A allele might be a preventive factor for this disease. Further well-designed researches with larger sample size and various regions are required to validate our conclusion.