IL-17A G197A and C1249T polymorphisms in gastric carcinogenesis

Interleukin 17A (IL-17A) is a critical cytokine involved in inflammatory diseases and inflammation-associated cancers. Increasing case-control studies have implicated crucial roles of IL-17A single nucleotide polymorphisms (G197A and C1249T) in gastric carcinogenesis, but providing inconclusive findings. The present study is aimed to estimate the association of IL-17A G197A and C1249T polymorphisms with gastric cancer risk by pooling all available publications. A comprehensive literature search in PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), and Wanfang databases was performed for eligible publications from their inception up to May 5, 2014. The pooled odds ratios (ORs) with corresponding 95 % confidence intervals (CIs) were calculated to estimate the effect of IL-17A polymorphisms on gastric carcinogenesis. Stratified analysis by ethnicity, Helicobacter pylori (H. pylori) infection, and smoking status were also conducted. All analyses were performed by using the Stata 12.0 software. There were five case-control studies with 2,774 cases and 3,162 controls and two case-control studies with 620 cases and 1,123 controls on the susceptibility of IL-17A G197A and C1249T polymorphisms to gastric cancer, respectively. Significant association was observed between IL-17A G197A polymorphism and gastric cancer risk, particularly among Asians. The status of H. pylori infection and smoking did not influence this association. In addition, the IL-17A C1249T polymorphism did not confer a risk effect on gastric carcinogenesis. The pooled results were not materially altered by sensitivity analysis. We firstly show that the polymorphism of IL-17A G197A but not C1249T is a risk factor for gastric cancer.