Long non-coding RNA RP11-284P20.2 promotes cell proliferation and invasion in hepatocellular carcinoma by recruiting EIF3b to induce c-met protein synthesis.

A newly identified lncRNA designated as RP11-284P20.2 has been identified to be up-regulated in hepatocellular carcinoma (HCC), but its role in HCC remain poorly understood. Quantitative PCR and immunocytochemical analysis were performed using the HCC tissues to identify the potential interaction partners of RP11-284P20.2. Moreover, RP11-284P20.2 was knocked down in HCC cell lines, HepG2 and SMMC7721, to investigate the influence of this lncRNA on cell growth properties. Additionally, RNA fluorescence in situ hybridization and immunofluorescence, RNA immunoprecipitation, and RNA pull-down assays were performed to determine the interaction of RP11-284P20.2 with c-met mRNA and eukaryotic translation initiation factor 3b (EIF3b). Silencing RP11-284P20.2 inhibited cell viability, migration, invasion, and colony formation, and increased apoptosis. Overexpression of c-met abolished these effects of RP11-284P20.2 in HCC cells. Histopathological examination showed that HCC tissues with high RP11-284P20.2 expression had higher c-met protein level than that in HCC tissues with low RP11-284P20.2 expression. However, there was no positive correlation between the expression levels of RP11-284P20.2 and c-met mRNA. RP11-284P20.2 knockdown led to a decease in c-met protein expression level, but did not affect the c-met mRNA expression level. These data suggest that RP11-284P20.2 regulates c-met protein expression level, which is independent of c-Met mRNA expression level. It was also confirmed that RP11-284P20.2 has high affinity toward both c-met mRNA and EIF3b protein, and hence RP11-284P20.2 probably recruits EIF3b protein to c-met mRNA and further facilitates its translation. RP11-284P20.2 promotes cell proliferation and invasion in hepatocellular carcinoma by recruiting EIF3b to induce c-met protein synthesis.

The tumor suppressor DLC1 inhibits cancer progression and oncogenic autophagy in hepatocellular carcinoma.

Downregulation of deleted in liver cancer 1 (DLC1) is associated with poor prognosis of various cancers, but its functional mechanisms in hepatocellular carcinoma (HCC) remains unclear. In the present study, we investigated the roles of DLC1 in tumor progression and autophagy of HCC. We found that DLC1 was frequently downregulated in HCC tissues. Underexpression of DLC1 correlated with AFP level, vascular invasion, poor differentiation, and poor prognosis. In vitro assays revealed that DLC1 not only suppressed the proliferation, migration, and invasion of HCC cells, but also inhibited autophagy of HCC cells. Mechanistic investigation revealed that DLC1 decreased TCF4 expression and the interaction between ß-catenin and TCF4, then inactivated Wnt/ß-catenin signaling. Additionally, DLC1 suppressed the ROCK1 activity and the dissociation of the Beclin1-Bcl2 complex, thereby inhibiting autophagy of HCC cells. In conclusion, our findings imply that loss of DLC1 contributes to the progression and oncogenic autophagy of HCC.

Long Noncoding RNA HCAL Facilitates the Growth and Metastasis of Hepatocellular Carcinoma by Acting as a ceRNA of LAPTM4B.

Long noncoding RNAs (lncRNAs) are a new class of regulatory noncoding RNAs. Emerging evidences indicate that lncRNAs play a critical role in the development of hepatocellular carcinoma (HCC). Although several lncRNAs have been annotated, the association of most lncRNAs with HCC is unknown. In this study, we investigated lncRNA alterations in HCC by performing lncRNA microarray analysis. We identified a novel lncRNA called HCC-associated lncRNA (HCAL) that was highly expressed in HCC tissues. HCAL upregulation was clinically associated with poor differentiation, intravascular cancer embolus, and decreased survival of patients with HCC. HCAL silencing significantly inhibited the growth and metastasis of HCC cells both in vitro and in vivo. Interestingly, transcriptome-sequencing analysis of HCAL-knockdown cells showed alterations in some cancer-related pathways. Mechanistically, HCAL directly interacted with and functioned as a sponge for microRNAs such as miR-15a, miR-196a, and miR-196b to modulate LAPTM4B expression. Taken together, our findings suggest the presence of a novel lncRNA-miRNA-mRNA regulatory network, i.e., the HCAL-miR-15a/miR-196a/miR-196b-LAPTM4B network, in HCC and indicate that HCAL may be a potential target for treating HCC.

Integrated analysis of gene expression and DNA methylation changes induced by hepatocyte growth factor in human hepatocytes.

Hepatocellular carcinoma (HCC) is the one of most common malignant tumors. The tumor microenvironment has a role in not only supporting growth and survival of tumor cells, but also triggering tumor recurrence and metastasis. Hepatocyte growth factor (HGF), one of the important growth factors in the tumor microenvironment, has an important role in angiogenesis, tumorigenesis and regeneration. However, the exact mechanism by which HGF regulates HCC initiation and development via epigenetic reprogramming has remained elusive. The present study focused on the epigenetic modification and target tumor-suppressive genes of HGF treatment in HCC. Expression profiling and DNA methylation array were performed to investigate the function of HGF and examine global genomic DNA methylation changes, respectively. Integrated analysis of gene expression and DNA methylation revealed potential tumor suppressor genes (TSGs) in HCC. The present study showed the multiple functions of HGF in tumorous and non­tumorous pathways and global genomic DNA methylation changes. HGF treatment upregulated the expression of DNA methyltransferase 1 (DNMT1). Overexpression of DNMT1 in HCC patients correlated with the malignant potential and poor prognosis of HCC. Furthermore, integration analysis of gene expression and DNA methylation changes revealed novel potential tumor suppressor genes TSGs including MYOCD, PANX2 and LHX9. The present study has provided mechanistic insight into epigenetic repression of TSGs through HGF­induced DNA hypermethylation.

Mechanistic and biological significance of DNA methyltransferase 1 upregulated by growth factors in human hepatocellular carcinoma.

Dysregulation of growth factor signaling plays a pivotal role in controlling the malignancy phenotype and progression of hepatocellular carcinoma (HCC). However, the precise oncogenic mechanisms underlying transcription regulation of certain tumor suppressor genes (TSGs) by growth factors are poorly understood. In the present study, we report a novel insulin-like growth factor 1 (IGF1) pathway that mediates de novo DNA methylation and TSG (such as DLC1 and CHD5) silencing by upregulation of the DNA methyltransferase 1 (DNMT1) via an AKT/ß-transducin repeat-containing protein (ßTrCP)-mediated ubiquitin-proteasome pathway in HCC. Analysis of DNA methylation in CpG islands of target genes revealed high co-localization of DNMT1 and DNMT3B on the promoters of TSGs associated with enhanced CpG hypermethylation. Our results point to a novel epigenetic mechanism for growth factor-mediated repression of TSG transcription that involves DNA methylation.