Common SEP15 polymorphisms and susceptibility to cancer: a systematic review and meta-analysis

Background: Some studies have shown that genetic polymorphisms in the 15 kDa selenoprotein (SEP15) gene can alter the interaction of Sep15 protein with selenium (Se), which is associated with increased susceptibility to cancer. However, the results of other studies are conflicting and ambiguous. Methods: To evaluate the associations between two common SEP15 polymorphisms (rs5859 and rs5845) and susceptibility to cancer, we conducted a comprehensive literature research of several electronic database, including PubMed, EMBASE, Cochrane Library, and Web of Science. We enrolled all relevantly eligible studies that were published by December 17, 2016. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated. Results: A total of nine publications comprising 10 case-control studies were enrolled for two SEP15 polymorphisms (rs5859 and rs5845). For the rs5859 polymorphism, we enrolled 5,802 cases and 7,035 controls from seven case-control studies, whereas for the rs5845 polymorphism, three case-control studies comprising 1,168 cases and 1,397 controls were included. Overall, the results demonstrated that neither the rs5859 nor rs5845 polymorphism was related to cancer susceptibility. In addition, stratification analyses based on ethnicity, cancer type, Hardy Weinberg equilibrium (HWE) status, and source of control generated null results. Conclusions: The results of this study show that SEP15 polymorphisms (rs5859 and rs5845) are not risk factors for cancer. Future well-designed studies with larger sample sizes are needed to validate these findings.