miR-345 inhibits tumor metastasis and EMT by targeting IRF1-mediated mTOR/STAT3/AKT pathway in hepatocellular carcinoma.

MicroRNAs (miRNAs) have been reported to play critical roles in tumor progression including hepatocellular carcinoma (HCC). Thus, the underlying mechanisms need further investigation. Previous study reported that loss of miR-345 expression indicated a poor prognosis of HCC patients. This study evaluated whether loss of miR-345 could promote the tumor metastasis and epithelial-mesenchymal-transition (EMT) of HCC by targeting interferon regulatory factor 1 (IRF1)-mediated mTOR/STAT3/AKT signaling. Underexpression of miR-345 was identified in 65 cases of human HCC compared to matched tumor-adjacent tissues by qRT-PCR. Moreover, we found that reduced expression of mi-345 was observed in HCC cell lines. The restoration of miR-345 inhibited cell migration and invasion in HCCLM3 cells, while its loss facilitated the cell mobility of HepG2 cells. Furthermore, miR-345 over-expression reduced lung metastases of HCC cells in nude mice. Notably, miR-345 overexpression prohibited, while its knockdown enhanced the EMT process of HCC cell lines in vitro. Bioinformatics software predicted that IRF1 was a direct target of miR-345. We then observed the negative regulation of miR-345 on IRF1 protein expression and the direct binding between them was further verified by dual-luciferase assays in HCC cells. In addition, over-expression of IRF1 mRNA was inversely correlated with the level of miR-345 in HCC specimens. Restoration of IRF1 resulted in promoted EMT and cell mobility in miR-345 overexpressing HCCLM3 cells. It was found that mTOR/STAT3/AKT pathway and its downstream targets including Slug, Snail and Twist may be involved in IRF1 mediated EMT process. In conclusion, miR-345 acts as an inhibitor of EMT process in HCC cells by targeting IRF1 and this study highlights the potential effects of miR-345 on prognosis and treatment of HCC.