Increasing evidences demonstrate that miRNAs contribute to development and progression of hepatocellular carcinoma (HCC). Underexpression of miR-1296 is recently reported to promote growth and metastasis of human cancers. However, the expression and role of miR-1296 in HCC remain unknown. The levels of miR-1296 in HCC tissues and cells were detected by qRT-PCR. Immunoblotting and immunofluorescence were used for detection of epithelial-to-mesenchymal transition (EMT) progression in HCC cells. Transwell assays were performed to determine migration and invasion of HCC cells. A lung metastasis mouse model was used to evaluated metastasis of HCC in vivo. The putative targets of miR-1296 were disclosed by public databases and a dual-luciferase reporter assay. We found that the expression of miR-1296 was reduced in HCC tissues and cell lines, and it was associated with metastasis and recurrence of HCC. Notably, miR-1296 overexpression inhibited migration, invasion and EMT progress of HCCLM3 cells, while miR-1296 loss facilitated these biological behaviors of Hep3B cells in vitro and in vivo. In addition, miR-1296 inversely regulated SRPK1 abundance by directly binding to its 3′-UTR, which subsequently resulted in suppression of p-AKT. Either SRPK1 re-expression or PI3K/AKT pathway activation, at least partially, abolished the effects of miR-1296 on migration, invasion and EMT progress of HCC cells. Furthermore, miR-1296 and SRPK1 expression were markedly correlated with adverse clinical features and poor prognosis of HCC patients. We showed that hypoxia was responsible for the underexpression of miR-1296 in HCC. And the promoting effects of hypoxia on metastasis and EMT of HCC cells were reversed by miR-1296. Underexpression of miR-1296 potentially serves as a prognostic biomarker in HCC. Hypoxia-induced miR-1296 loss promotes metastasis and EMT of HCC cells probably by targeting SRPK1/AKT pathway.

Protein arginine methyltransferases (PRMT) catalyze protein arginine methylation and play an important role in many biological processes. Aberrant PRMT expression in tumor cells has been documented in several common cancer types; however, its precise contribution to hepatocellular carcinoma (HCC) cell invasion and metastasis is not fully understood. In this study, we identified a new oncogene, PRMT9, whose overexpression strongly promotes HCC invasion and metastasis. PRMT9 expression was detected more frequently in HCC tissues than in adjacent noncancerous tissues. PRMT9 overexpression was significantly correlated with hepatitis B virus antigen (HBsAg) status, vascular invasion, poor tumor differentiation and advanced TNM stage. Patients with higher PRMT9 expression had a shorter survival time and higher recurrence rate. PRMT9 expression was an independent and significant risk factor for survival after curative resection. Functional studies demonstrated that PRMT9 increased HCC cell invasion and lung metastasis. Knocking down PRMT9 with short hairpin RNA (shRNA) inhibited HCC cell invasion. Further investigations found that PRMT9 increased cell migration and invasion through epithelial‐mesenchymal transition (EMT) by regulating Snail expression via activation of the PI3K/Akt/GSK‐3β/Snail signaling pathway. In clinical HCC samples, PRMT9 expression was positively associated with Snail expression and was negatively associated with E‐cadherin expression. In conclusion, our study demonstrated that PRMT9 is an oncogene that plays an important role in HCC invasion and metastasis through EMT by regulating Snail expression via activation of the PI3K/Akt/GSK‐3β/Snail signaling pathway. Thus, PRMT9 may serve as a candidate prognostic biomarker and a potential therapeutic target.

Increasing evidence suggests that PRMT5, a protein arginine methyltransferase, has roles in cell growth regulation and cancer development. However, the role of PRMT5 in hepatocellular carcinoma (HCC) progression remains unclear. Here, we showed that PRMT5 expression was frequently upregulated in HCC tissues, and its expression was inversely correlated with overall survival in HCC patients. PRMT5 knockdown markedly inhibited in vitro HCC proliferation and in vivo tumorigenesis. We revealed that the mechanism of PRMT5‐induced proliferation was partially mediated by BTG downregulation, leading to cell cycle arrest during the G1 phase in HCC cells. Ectopic BTG2 overexpression decreased HCC growth, caused cell cycle arrest at the G1 phase, and downregulated Cyclin D1 and Cyclin E1 protein expression. Furthermore, we found that PRMT5‐induced ERK phosphorylation regulated BTG2 expression in HCC cells, whereas pretreatment with a selective ERK1/2 inhibitor (PD184352) significantly reversed the effect of PRMT5 on BTG2 expression. Our results indicated that PRMT5 promotes HCC proliferation by downregulating BTG2 expression via the ERK pathway.

Long noncoding RNAs (lncRNAs) are involved in a variety of biological processes such as tumor proliferation and metastasis. A close relationship between hepatitis B virus X protein (HBx) and SMYD3 in promoting the proliferation and metastasis of hepatocellular carcinoma (HCC) was recently reported. However, the exact oncogenic mechanism of HBx-SMYD3 remains unknown. In this study, by performing lncRNA microarray analysis, we identified a novel lncRNA that was regulated by both HBx and SMYD3, and we named it lncIHS (lncRNA intersection between HBx microarray and SMYD3 microarray). lncIHS was overexpressed in HCC and decreased the survival rate of HCC patients. Knockdown of lncIHS inhibited HCC cell migration, invasion, and proliferation, and vice versa. Further study showed that lncIHS positively regulated the expression of epithelial mesenchymal transition (EMT)-related markers c-Myc and Cyclin D1, as well as the activation of the ERK- and AKT-signaling pathways. lncIHS exerted its oncogenic effect through ERK and AKT signaling. Moreover, results from transcriptome-sequencing analysis and mass spectrometry showed that lncIHS regulated multiple genes that were the upstream molecules of the ERK- and AKT-signaling pathways. Therefore, our findings suggest a regulatory network of ERK and AKT signaling through lncIHS, which is downstream of HBx-SMYD3, and they indicate that lncIHS may be a potential target for treating HCC.