miR-187-3p inhibits the metastasis and epithelial–mesenchymal transition of hepatocellular carcinoma by targeting S100A4

• miR-187-3p is significantly down-regulated in HCC, and is correlated with adverse clinical features and poor prognosis of HCC patients.
• miR-187-3p can inhibit the metastasis of HCC cells by regulating EMT phenotype.
• S100A4 is a direct downstream target of miR-187-3p, and mediated the biological function of miR-187-3p in HCC.
• miR-187-3p is down-regulated by hypoxia, and is involved in the metastasis and EMT of HCC cells promoted by hypoxia.

miR-187-3p, a novel cancer-related microRNA, was previously reported to play promoting or suppressive roles in different malignancies. However, the expression level, biological function, and underlying mechanisms of miR-187-3p in hepatocellular carcinoma (HCC) remain unknown. This study demonstrated that miR-187-3p was significantly down-regulated in HCC tissues and cell lines, and was associated with advanced TNM stage and metastasis in HCC. Functional studies confirmed that miR-187-3p could inhibit the metastasis of HCC both in vitro and in vivo. Moreover, we proved that miR-187-3p could prevent the epithelial–mesenchymal transition (EMT) of HCC cells. Mechanically, S100A4 was a direct downstream target of miR-187-3p, and mediated the functional influence of miR-187-3p in HCC. Furthermore, miR-187-3p and S100A4 expression was evidently correlated with adverse clinical features and poor prognosis of HCC. Lastly, we showed that hypoxia was responsible for the significantly decreased level of miR-187-3p in HCC, and miR-187-3p was involved in the promoting effects of hypoxia on the metastasis and EMT of HCC cells. Taken together, miR-187-3p inhibits the metastasis and EMT in HCC by targeting S100A4. miR-187-3p can serve as a prognostic indicator and a promising therapeutic target for HCC patients.