Genetic polymorphism at miR-181a binding site contributes to gastric cancer susceptibility.

Recent evidences show that genetic polymorphisms falling in miRNA binding sites can alter the strength of miRNA binding and disturb miRNA-mediated posttranscriptional regulation. Our study aimed to investigate the role of single-nucleotide polymorphisms (SNPs) in putative miRNA binding sites in gastric cancer (GC). Based on microarray and quantitative reverse transcription PCR analyses, we found that miR-181a was significantly upregulated in GC tissues. Bioinformatics survey was used to explore SNPs within miR-181a binding sites. Three SNPs were genotyped in a case-control study (500 cases and 502 controls). The T allele genotypes (rs12537CT and TT) of MTMR3 were found associated with significantly increased GC risk [adjusted odds ratio 1.72, 95% confidence interval (CI) 1.36-2.16, P = 3.99×10(-5)] and poor overall survival [hazard ratio (HR) 1.38, 95% CI 1.03-1.83, P = 0.029], although they were not an independent prognostic factor in multivariate Cox regression analysis (HR 1.28, 95% CI 0.95-1.72, P = 0.11). We further demonstrated that the rs12537CT genotype carriers had lower MTMR3 mRNA expression levels than CC genotype carriers in GC tissues (P = 0.013), whereas no significant difference in miR-181a expression levels was found (P = 0.135). Luciferase assay revealed that miR-181a directly targeted MTMR3, and its suppressive effect was enhanced when the rs12537C allele was substituted by T variant, although the difference was not significant (P = 0.055). Our study suggested that rs12537 is associated with susceptibility and prognosis of GC in southern Han Chinese, and miR-181a and its target gene MTMR3 play important roles in GC.