Hepatocellular carcinoma (HCC) is the third cause of cancer-related deaths worldwide. Sorafenib is the only approved drug for patients with advanced HCC but has shown limited activity. microRNAs (miRs) have been involved in several neoplasms including HCC suggesting their use or targeting as good tools for HCC treatment. The purpose of this study was to identify novel approaches to sensitize HCC cells to sorafenib through miRs. miR-423-5p was validated as positive regulator of autophagy in HCC cell lines by transient transfection of miR and anti-miR molecules. miR-423-5p expression level was evaluated by real-time polymerase chain reaction (PCR) in sera collected from 39 HCC patients before and after treatment with sorafenib. HCC cells were cotreated with sorafenib and miR-423-5p and the effects on cell cycle, apoptosis, and autophagy were evaluated. Secretory miR-423-5p was upregulated both in vitro and in vivo by sorafenib treatment and its increase was correlated with response to therapy since 75% of patients in which an increase of secretory miR423-5p was found were in partial remission or stable disease after 6 moths from the beginning of therapy. HCC cells transfected with miR-423-5p showed an increase of cell percentage in S-phase of cell cycle paralleled by a similar increase of autophagic cells evaluated at both fluorescence activated cell sorter (FACS) and transmission electron microscopy. Our results suggest the miR423-5p can be used as a useful tool to predict response to sorafenib in HCC patients and is involved in autophagy regulation in HCC cells.

Sorafenib is an antitumor drug for treatment of advanced hepatocellular carcinoma (HCC). It acts as a multikinase inhibitor suppressing cell proliferation and angiogenesis. Human microRNA-125a-5p (miR-125a) is endowed with similar activities and is frequently downregulated in HCC. Looking for a potential microRNA-based mechanism of action of the drug, we found that sorafenib increases cellular expression of miR-125a in cultured HuH-7 and HepG2 HCC cells. Upregulation of the microRNA inhibited cell proliferation by suppression of sirtuin-7, a NAD(+)-dependent deacetylase, and p21/p27-dependent cell cycle arrest in G1. Later, recruitment of miR-125a in the antiproliferative activity of sorafenib was inquired by modulating its expression in combination with the drug treatment. This analysis showed that intracellular delivery of miR-125a had no additive effect on the antiproliferative activity of sorafenib, whereas a miR-125a inhibitor could counteract it. Finally, evaluation of other oncogenic targets of miR-125a revealed its ability to interfere with the expression of matrix metalloproteinase-11, Zbtb7a proto-oncogene, and c-Raf, possibly contributing to the antiproliferative activity of the drug. J. Cell. Physiol. 232: 1907-1913, 2017. © 2016 Wiley Periodicals, Inc.

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MicroRNA-125a-5p (miR-125a) is a vertebrate homolog of lin-4, the first discovered microRNA, and plays a fundamental role in embryo development by downregulating Lin-28 protein. MiR-125a is also expressed in differentiated cells where it generally acts as an antiproliferative factor by targeting membrane receptors or intracellular transductors of mitogenic signals. MiR-125a expression is downregulated in several tumors, including hepatocellular carcinoma (HCC) where it targets sirtuin-7, matrix metalloproteinase-11, VEGF-A, Zbtb7a, and c-Raf. In this study, we have isolated the transcription promoter of human miR-125a and characterized its activity in HCC cells. It is a TATA-less Pol II promoter provided with an initiator element and a downstream promoter element, located 3939 bp upstream the genomic sequence of the miRNA. The activity of the promoter is increased by the transcription factor NF-kB, a master regulator of inflammatory response, and miR-125a itself was found to strengthen this activation through inhibition of TNFAIP3, a negative regulator of NF-kB. This finding contributes to explain the increased levels of miR-125a observed in the liver of patients with chronic hepatitis B.