SMC4 enhances the chemoresistance of hepatoma cells by promoting autophagy.

Background: Drug resistance is a major contributing factor to chemotherapy failure in hepatocellular carcinoma (HCC) patients. However, the exact mechanism underlying the chemoresistance of HCC remains unknown. Methods: HepG2 cells were incubated with different concentrations of 5-fluorouracil (5-FU), and the Cell Counting Kit-8 assay was used to test the cell survival rate. The expression level of structural maintenance of chromosome 4 (SMC4) in drug-resistant cells was analyzed by real-time quantitative polymerase chain reaction (PCR) and western blotting. To assess autophagy, immunofluorescence was applied to detect the light chain 3 beta (LC3B) level in HepG2/5-FU cells. To further study the upstream regulation of miR (microRNA)-219/SMC4, a gene chip assay was performed. A luciferase reporter assay was used to determine whether long non-coding RNA-XIST (lncRNA-XIST) functions as a competitive endogenous RNA (ceRNA) for miR-219. Cellular proliferation was evaluated using MTT [3-(4,5)-dimethylthiahiazo (-z-y1)-2,5-di-phenytetrazoliumromide] and colony formation assays, wound healing and invasion assays were performed to study the invasion and migration ability of the cells, and flow cytometry assays were carried out to evaluate cell apoptosis. Results: In the present study, we established a drug-resistant hepatoma cell line named HepG2/5-FU. We confirmed that SMC4 may play an important role in hepatoma cell autophagy and could promote autophagy to increase the drug resistance of hepatoma cells. We also demonstrated that lncRNA-XIST may competitively bind to miR-219 by acting as a miRNA sponge, thereby preventing miR-219 from effectively reducing the expression of SMC4 and further affecting the autophagy and drug resistance of hepatoma cells via the adenosine 5'-monophosphate (AMP)-activated protein kinase/mechanistic target of rapamycin (AMPK/mTOR) pathway. Conclusions: Our study suggests that SMC4 may be a potential marker of a poor HCC response to chemotherapy and a novel therapeutic target for HCC chemotherapy.

Circ-IGF1R has pro-proliferative and anti-apoptotic effects in HCC by activating the PI3K/AKT pathway.

Circular RNAs (circRNAs), a novel class of widespread and diverse endogenous RNAs, have been identified as critical regulators of various cancers, including hepatocellular carcinoma (HCC). However, the specific roles of circRNAs in HCC are largely unknown. In this study, we identified a novel circRNA, circ-IGF1R, in HCC tumour tissues and cell lines. Circ-IGF1R levels were found to be significantly upregulated in HCC tissues compared with levels in paired peritumoural tissues. The high expression levels of circ-IGF1R in HCC were associated with tumour size. Moreover, knocking down circ-IGF1R with siRNA significantly attenuated cell proliferation and induced cell apoptosis and cell cycle arrest in vitro. Further investigation revealed that PI3K/AKT signalling pathway activation was involved in the oncogenic functions of circ-IGF1R in HCC. Our study suggests that circ-IGF1R may be a potential target for the prevention and treatment of HCC.

The mRNA, miRNA and lncRNA networks in hepatocellular carcinoma: An integrative transcriptomic analysis from Gene Expression Omnibus.

Research advances and analysis in the non­protein coding part of the human genome have suggested that microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are associated with tumor initiation, growth and metastasis. Accumulating studies have demonstrated that a class of miRNAs and lncRNAs are dysregulated in hepatocellular carcinoma (HCC) and closely associated with tumorigenesis, diagnosis and prognosis. In the present study, integrative analysis of published data on multi­level Gene Expression Omnibus (GEO) and a bioinformatics computational approach were used to predict regulatory mechanism networks among differentially expressed mRNAs, miRNAs, and lncRNAs. Firstly, nine microarray expression data sets of mRNAs, miRNAs, and lncRNAs associated with HCC were collected from GEO datasets. Secondly, a total of 628 mRNAs, 15 miRNAs, and 49 lncRNAs were differentially expressed in this integrative analysis. Following this, mRNA, miRNA and lncRNA regulatory or co­expression networks were constructed. From the construction of the regulatory networks, five miRNAs and ten lncRNAs were identified as key differentially expressed noncoding RNAs associated with HCC progression. Finally, the regulatory effects of ten lncRNAs and miRNAs were validated. The study provides a novel insight into the understanding of the transcriptional regulation of HCC, and differentially expressed lncRNAs targeted and regulated by miRNAs were identified and validated in HCC specimens and cell lines.

Upregulated long non-coding RNA LOC90784 promotes cell proliferation and invasion and is associated with poor clinical features in HCC.

A growing amount of literature has indicated that long non-coding RNAs (lncRNAs) are important factors in hepatocellular carcinoma (HCC) progression. However, the significance of lncRNAs in the progression and prognosis of liver cancer is largely unknown. In the present study, upregulated lncRNA LOC90784 was identified through integrative analysis of GSE58043 and GSE55191. Furthermore, associations between LOC90784 expression and the clinicopathological characteristics of patients were analyzed with a validated cohort 1 and the Cancer Genome Atlas (TCGA) cohort 2. We investigated the mechanisms by which this highly expressed lncRNA promotes HCC proliferation, invasion and migration via qRT-PCR, fluorescence in situ hybridization (FISH) staining, siRNA transfection, cell proliferation assays, Transwell and colony formation assays, flow cytometry analysis and Western blot. The results showed that LOC90784 expression levels were significantly higher in HCC cell lines and tissues and mainly localized in the cytoplasm. Knockdown of lncRNA LOC90784 expression inhibited proliferation and induced apoptosis and cell cycle arrest by promoting Bax and repressing CDK4 and Cyclin D1 protein expression; it also inhibited invasion and migration by repressing MMP2 and MMP9 expression in HCC cells. LOC90784 overexpression was associated with poor clinical features in the two cohorts and poor overall survival rates in HCC patients with clear resection margins (R0) in cohort 2. These results indicated that LOC90784 upregulation may be a critical oncogene and potential new biomarker in HCC.