Methylation-regulated miR-124-1 suppresses tumorigenesis in hepatocellular carcinoma by targeting CASC3

This study was to investigate the roles and mechanisms of miR-124-1 in hepatocellular carcinoma (HCC). We analyzed the expression of miR-124-1 in human HCC tissues and cell lines. Luciferase reporter assays were used to analyze the target of miR-124-1. Human HCC cell lines were transduced with lentiviruses expressing miR-124-1, and proliferation and colony formation were analyzed. The growth of human HCC cells overexpressing miR-124-1 was assessed in nude mice. The expression of p38-MAPK, JNK, ERK and related signaling molecules was detected by western blotting and immunohistochemistry. Our results showed that miR-124-1 levels were reduced in HCC tissues and cell lines compared with those in adjacent non-cancer tissues and normal liver cell lines respectively. Downregulation of miR-124-1 in HCC cell lines were attributed to hypermethylation of its promoter region. Overexpression of miR-124-1 inhibited HCC cell proliferation in vitro, whereas miR-124-1 was correlated with clinicopathological parameters of HCC patients. HCC cell-mediated overexpression of miR-124-1 in nude mice suppressed tumor growth. Cancer susceptibility candidate 3 (CASC3) was identified as a direct target of miR-124-1 by computational analysis and experimental assays. MiR-124-1-mediated downregulation of CASC3 resulted in the inactivation of p38-MAPK, JNK and ERK. Our findings provide potential new targets for the prevention or treatment of HCC.