MicroRNAs (miRNAs) have been found to play fundamental roles in the pathogenesis of hepatocellular carcinoma (HCC). Previous miRNA array data showed that miR-519a was upregulated in HCC tissues compared to adjacent non-tumor tissues. However, the functional role of miR-519a in HCC remains unexplored. In this study, we demonstrated that the expression of miR-519a was elevated in both HCC tissues and cell lines. Clinical association analysis revealed that high expression of miR-519a was correlated with adverse clinicopathological characteristics including large tumor size, high Edmondson-Steiner grading, advanced tumor-node-metastasis (TNM) tumor stage and venous infiltration. Furthermore, high expression of miR-519a conferred a reduced 5-year overall survival and disease-free survival of HCC patients. Moreover, we disclosed that miR-519a overexpression promoted, but miR-519a silencing reduced, HCC cell proliferation and cell cycle progression in vitro. Notably, we identified phosphatase and tensin homolog (PTEN) as a direct downstream target and functional mediator of miR-519a in HCC cells. Mechanistically, phosphatidylinositol-3-OH kinase (PI3K)/AKT pathway, downstream of PTEN, is essential for the functional roles of miR-519a in HCC cells. In conclusion, our results indicate that miR-519a promotes tumor growth of HCC by targeting PTEN-mediated PI3K/AKT pathway, and potentially serves as a novel prognostic biomarker and therapeutic target for HCC.

In HCC, reduced Fbxw7 expression closely correlated with clinicopathological characteristics and may have prognostic potential through the enhanced function of cell cycle regulatory proteins.

Human sulfatase 2 (SULF2) functions as an oncoprotein in hepatocellular carcinoma (HCC) development by promoting tumor growth and metastasis via enhancement of fibroblast growth factor-2/extracellular signal-regulated kinase and WNT/ β-catenin signaling. Recent results implicate that SULF2 activates the transforming growth factor beta (TGFB) and Hedgehog/GLI1 pathways in HCC. OKN-007 is a novel phenyl–sulfonyl compound that inhibits the enzymatic activity of SULF2. To investigate the antitumor effect of OKN-007 in HCC, we treated Huh7 cells, which express high levels of SULF2, with OKN-007 and found that it significantly promoted tumor cell apoptosis and inhibited cell proliferation, viability, and migration. To understand the action of OKN-007 on SULF2, we used Huh7 cells which normally express SULF2 and Hep3B cells that do not normally express SULF2. Utilizing Huh7 cells transfected with short hairpin RNA targeting SULF2 and transfection of Hep3B cells with a SULF2 plasmid to enhance SULF2 expression, we showed that the antitumor activity of OKN-007 was more pronounced in cells expressing SULF2. Furthermore, in vivo experiments verified that OKN-007 repressed tumor growth significantly. These results identify SULF2 as an important target of the antitumor effect of OKN-007. To determine the molecular mechanism of the antitumor effect of OKN-007, both TGFB1/SMAD and Hedgehog/GLI1 signaling pathway activity were measured by Western blot and SMAD- or GLI-reporter luciferase assays. We found that both signaling pathways were inhibited by OKN-007. Together, these results show that OKN-007 can suppress TGFB1/SMAD and Hedgehog/GLI1 signaling via its inhibition of SULF2 enzymatic activity. We conclude that OKN-007 or more potent derivatives may be promising agents for the treatment of HCC.

Background Long non-coding RNAs (lncRNAs) are widely involved in human cancers’ progression by regulating tumor cells’ various malignant behaviors. MAPKAPK5-AS1 has been recognized as an oncogene in colorectal cancer. However, the biological role of MAPKAPK5-AS1 in hepatocellular carcinoma (HCC) has not been explored. Methods Quantitative real-time PCR was performed to detect the level of MAPKAPK5-AS1 in HCC tissues and cell lines. The effects of MAPKAPK5-AS1 on tumor growth and metastasis were assessed via in vitro experiments, including MTT, colony formation, EdU, flow cytometry, transwell assays, and nude mice models. The western blotting analysis was carried out to determine epithelial-mesenchymal transition (EMT) markers and AKT signaling. The interaction between MAPKAPK5-AS1, miR-154-5p, and PLAGL2 were explored by luciferase reporter assay and RNA immunoprecipitation. The regulatory effect of HIF-1α on MAPKAPK5-AS1 was evaluated by chromatin immunoprecipitation. Results MAPKAPK5-AS1 expression was significantly elevated in HCC, and its overexpression associated with malignant clinical features and reduced survival. Functionally, MAPKAPK5-AS1 knockdown repressed the proliferation, mobility, and EMT of HCC cells and induced apoptosis. Ectopic expression of MAPKAPK5-AS1 contributed to HCC cell proliferation and invasion in vitro. Furthermore, MAPKAPK5-AS1 silencing suppressed, while MAPKAPK5-AS1 overexpression enhanced HCC growth and lung metastasis in vivo. Mechanistically, MAPKAPK5-AS1 upregulated PLAG1 like zinc finger 2 (PLAGL2) expression by acting as an endogenous competing RNA (ceRNA) to sponge miR-154-5p, thereby activating EGFR/AKT signaling. Importantly, rescue experiments demonstrated that the miR-154-5p/PLAGL2 axis mediated the function of MAPKAPK5-AS1 in HCC cells. Interestingly, we found that hypoxia-inducible factor 1α (HIF-1α), a transcript factor, could directly bind to the promoter to activate MAPKAPK5-AS1 transcription. MAPKAPK5-AS1 regulated HIF-1α expression through PLAGL2 to form a hypoxia-mediated MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop in HCC. Conclusions Our results reveal a MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop in HCC progression and suggest that MAPKAPK5-AS1 could be a potential novel therapeutic target of HCC.