Polymorphisms in pre-miRNAs may affect its expression, then have effect on its target mRNAs and be associated with cancer susceptibility. In this study, we evaluated the association of an indel polymorphism rs57408770 in pre-miR-3131 with hepatocellular carcinoma (HCC) susceptibility in a Chinese population. The contribution of rs57408770 to HCC risk was investigated in two independent case-control sets (1051 HCC and 1058 controls). Logistic regression analysis showed that the insertion allele of rs57408770 was significantly associated with an increased risk for HCC occurrence in both case-control studies. Moreover, the results of genotype-phenotype correlation analysis from both in vivo and in vitro experiments showed that the insertion allele was significantly correlated with higher expression of mature miR-3131 comparing with the deletion allele. The RNA-Binding Protein Immunoprecipitation assay results indicated that rs57408770 could affect the expression level of mature miR-3131 probably through disturbing the binding of splicing factor SRp20 with pre-miR-3131. Furthermore, overexpression of miR-3131 displayed a proliferation promoting and anti-apoptosis effect on HCC cell lines, suggesting that miR-3131 may act as a proto-oncogene in HCC. Finally, human genome-wide gene expression profile assay was used to screen the targets of miR-3131. The overexpressed miR-3131 could lead to a significant decrease of DTHD1 and XAF1 mRNA level. Taken together, our findings provided evidence that rs57408770 may play a functional role in the carcinogenesis of HCC by affecting SRp20 binding with pre-miR-3131 and affecting the expression of mature miR-3131, subsequently affecting the expression of DTHD1 and XAF1, thus confers risk for HCC.
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