MicroRNA-155-5p promotes hepatocellular carcinoma progression by suppressing PTEN through the PI3K/Akt pathway

MicroRNA-155-5p (miR-155-5p) has been reported to play an oncogenic role in different human malignancies; however, its role in hepatocellular carcinoma (HCC) progression is not clearly understood. In this study, we used real-time PCR in 20 rats with chemically-induced HCC, 28 human HCC tissues, and the matched paracarcinoma tissues, and HCC cell lines to determine the expression patterns of miR-155-5p and PTEN mRNA. Algorithm-based and experimental strategies, such as dual luciferase gene reporter assays, real-time PCR and western blots were used to identify PTEN as a candidate miR-155-5p target. Gain- and loss-of-function experiments and administration of a PI3K/Akt pathway inhibitor (wortmannin) were used to identify the effects of miR-155-5p and PTEN in MTT assays, flow cytometric analysis, wound healing assays and transwell assays. The results showed that miR-155-5p was highly overexpressed; however, PTEN was underexpressed in the HCC rat models, human HCC tissues and cell lines. In addition, miR-155-5p upregulation and PTEN downregulation were significantly associated with TNM stage (P < 0.05). Through in vitro experiments, we found that miR-155-5p promoted proliferation, invasion and migration, but inhibited apoptosis in HCC by directly targeting the 3′-UTR of PTEN. Western blots showed that miR-155-5p inactivated Bax and caspase-9, but activated Bcl-2 to inhibit apoptosis, and it activated MMP to promote migration and invasion via the PI3K/Akt pathway. A xenograft tumor model was used to demonstrate that miR-155-5p targets PTEN and activates the PI3K/Akt pathway in vivo as well. Our study highlighted the importance of miR-155-5p and PTEN associated with aggressive HCC both in vitro and in vivo.