Linhui Liang

Circular RNA profiling reveals an abundant circHIPK3 that regulates cell growth by sponging multiple miRNAs

Circular RNAs (circRNAs) represent a class of widespread and diverse endogenous RNAs that may regulate gene expression in eukaryotes. However, the regulation and function of human circRNAs remain largely unknown. Here we generate ribosomal-depleted RNA sequencing data from six normal tissues and seven cancers, and detect at least 27,000 circRNA candidates. Many of these circRNAs are differently expressed between the normal and cancerous tissues. We further characterize one abundant circRNA derived from Exon2 of the HIPK3 gene, termed circHIPK3. The silencing of circHIPK3 but not HIPK3 mRNA significantly inhibits human cell growth. Via a luciferase screening assay, circHIPK3 is observed to sponge to 9 miRNAs with 18 potential binding sites. Specifically, we show that circHIPK3 directly binds to miR-124 and inhibits miR-124 activity. Our results provide evidence that circular RNA produced from precursor mRNA may have a regulatory role in human cells.

MicroRNA-30d-5p inhibits tumour cell proliferation and motility by directly targeting CCNE2 in non-small cell lung cancer

MicroRNAs (miRNAs) are small, single-stranded, non-coding RNA molecules that are dysregulated in many types of human cancers, although their precise functions in driving non-small cell lung cancer (NSCLC) are incompletely understood. In the present study, we found that miR-30d-5p, often downregulated in NSCLC tissues, significantly inhibited the growth, cell cycle distribution, and motility of NSCLC cells. Furthermore, we demonstrated that cyclin E2 (CCNE2), which was often upregulated in NSCLC tissues, was a direct target of miR-30d-5p. CCNE2 expression promoted the proliferation, invasion, and migration of NSCLC cells. In addition, the re-introduction of CCNE2 expression antagonised the inhibitory effects of miR-30d-5p on the capacity of NSCLC cells for proliferation and motility. Together, these results suggest that the miR-30d-5p/CCNE2 axis may contribute to NSCLC cell proliferation and motility, indicating miR-30d-5p as a potential therapeutic target for the treatment of NSCLC.

miR-192, a prognostic indicator, targets the SLC39A6/SNAIL pathway to reduce tumor metastasis in human hepatocellular carcinoma

Metastasis is one of the causes of cancer death. Functions and mechanisms of microRNAs (miRNAs) involved in hepatocellular carcinoma (HCC) metastasis are largely unknown. Here, a miRNA microarray analysis was performed in MHCC-97L, MHCC-97H and HCC-LM3 cells with gradually increasing metastatic potential to disclose crucial miRNAs involved in HCC metastasis. miR-192 expression decreased and negatively correlated with vascular invasion in HCC specimens. Gain and loss of function studies revealed that miR-192 significantly suppressed metastasis of HCC cells in vitro and in vivo. Solute carrier family 39 member 6 (SLC39A6) was identified as a direct and functional target of miR-192. In addition, SLC39A6 negatively correlated with miR-192 in HCC samples and promoted HCC cell migration and invasion. Moreover, miR-192 decreased SLC39A6 expression, subsequently downregulating SNAIL and upregulating E-cadherin expression. Suppression of migration and invasion caused by miR-192 overexpression was alleviated by exogenous Snail expression. Intriguingly, lower miR-192 expression and higher SLC39A6 expression significantly contributed to poorer outcomes in HCC patients. Multivariate analysis indicated that miR-192 was an independent and significant predictor of HCC patient overall survival. In conclusion, we newly determined that miR-192 targeted the SLC39A6/SNAIL pathway to reduce tumor metastasis in HCC cells. This axis provided insights into the mechanism underlying miRNA regulation of HCC metastasis and a novel therapeutic target for HCC treatment.

NF-κB signaling relieves negative regulation by miR-194 in hepatocellular carcinoma by suppressing the transcription factor HNF-1α

Activation of NF-κB signaling in liver cancer cells suppresses a microRNA that usually limits NF-κB activity. A cancerous inflammatory feedback loop Inflammation activates NF-κB signaling in cells, and chronic inflammation contributes to the development and progression of many cancers, including hepatocellular carcinoma (HCC). In HCC patient tumors, Bao et al. found that NF-κB activity was increased and that the abundance of a microRNA, miR-194, was decreased. Expressing miR-194 in HCC cells suppressed NF-κB activity and decreased both cell migration in culture and lung colonization after injection into mice. However, stimulating NF-κB signaling with the inflammatory cytokine TNFα reduced the abundance of a transcription factor (HNF-1α), leading to a decrease in the expression of miR-194 and promoting cell migration in culture. Thus, by shutting off the expression of a microRNA, proinflammatory cytokines trigger persistent NF-κB signaling that enables chronic inflammation to promote metastatic progression of liver cancer. Constitutive activation of the proinflammatory transcription factor nuclear factor κB (NF-κB) plays an important role in progression of hepatocellular carcinoma (HCC). Emerging modulators of NF-κB signaling are noncoding RNAs, especially microRNAs (miRNAs). We previously identified miRNAs that reduced the induction of NF-κB activity upon addition of tumor necrosis factor–α (TNFα) to HCC cells. We found that among these miRNAs, the abundance of liver-enriched miR-194 was decreased in HCC tissue and that low abundance of miR-194 correlated with a high occurrence of vascular invasion. Overexpressing miR-194 suppressed HCC cell migration and invasiveness in culture and metastatic seeding in mice. Transcripts encoding tripartite motif containing 23 (TRIM23), a ubiquitin ligase involved in NF-κB activation, and chromosome 21 open reading frame 91 (C21ORF91), a protein of unknown function, were identified as direct targets of miR-194 in HCC cells; knocking down either protein decreased the activity of a luciferase NF-κB reporter. Furthermore, the NF-κB pathway activator TNFα, an inflammatory cytokine, inhibited the transcription of miR-194 by decreasing the abundance of hepatocyte nuclear factor–1α (HNF-1α). The abundance of miR-194 positively correlated with that of HNF-1α and inversely correlated with that of TNFα in human HCC tissue. Thus, we identified a pathway in which TNFα–NF-κB signaling switches off negative regulation by suppressing HNF-1α–mediated expression of miR-194, revealing insight into the mechanisms linking inflammatory pathways, miRNA, and HCC metastasis.

MicroRNA-127-5p targets the biliverdin reductase B/nuclear factor-κB pathway to suppress cell growth in hepatocellular carcinoma cells.

Nuclear factor‐κB (NF‐κB) activation is one of the major mediators of inflammation‐induced cancer cell growth and progression. In previous studies, we screened a series of microRNAs (miRNAs) that targeted the NF‐κB signaling pathway. In this study, we showed that miR‐127‐5p suppressed NF‐κB activity through inhibition of p65 nuclear translocation. In addition, miR‐127‐5p also inhibited the transcription of downstream targets of the NF‐κB signaling pathway. While exploring the mechanism of the inhibition of NF‐κB activity by miR‐127‐5p, we found that miR‐127‐5p decreased the phosphorylation of p65. MicroRNA‐127‐5p inhibited the growth and colony formation of hepatocellular carcinoma (HCC) cells and decreased biliverdin reductase B (BLVRB) expression by directly binding to its 3′‐UTR. RNA interference of BLVRB suppressed HCC cell growth, whereas the overexpression of BLVRB promoted HCC cell growth. Furthermore, BLVRB blockade inhibited the phosphorylation of p65 protein and the expression of downstream targets of the NF‐κB signaling pathway, mimicking the function of miR‐127‐5p. The restoration of BLVRB in HCC cells overexpressing miR‐127‐5p impaired the suppression of HCC growth by miR‐127‐5p. Moreover, miR‐127‐5p was downregulated in 58% of HCC samples. In summary, we found that miR‐127‐5p suppressed NF‐κB activity by directly targeting BLVRB in HCC cells, and this finding improves our understanding of the molecular mechanism of inflammation‐induced HCC growth and proliferation and the successful inhibition of NF‐κB activity by cancer treatment.

GNAI3 inhibits tumor cell migration and invasion and is post-transcriptionally regulated by miR-222 in hepatocellular carcinoma

Guanine nucleotide binding protein, alpha inhibiting activity polypeptide 3 (GNAI3) is involved in many biological processes. However, its biological function in hepatocellular carcinoma (HCC) remains unclear. An immunohistochemical staining analysis revealed that GNAI3 protein was down-regulated in HCC compared to non-cancerous liver. Furthermore, transwell assays indicated that GNAI3 inhibits HCC cell migration and invasion. Using software predictions and experimental screening, we found that miR-222 could directly bind to GNAI3 mRNA and decrease GNAI3 protein expression in HCC cells. Moreover, miR-222 was up-regulated in HCC and negatively correlated with GNAI3 protein expression. These results indicated that down-regulation of GNAI3 might be caused by up-regulation of miR-222 in HCC. In conclusion, GNAI3 was down-regulated by miR-222 in HCC, and this deregulation promoted migration and invasion of HCC. These findings extended our insight into the complex molecular mechanisms underlying the invasion and metastasis of HCC and may provide new therapeutic targets.

Role of microRNAs in inflammation-associated liver cancer

Liver cancer, primarily hepatocellular carcinoma (HCC), is a major cause of cancer-related death worldwide. HCC is a suitable model of inflammation-induced cancer because more than 90% of HCC cases are caused by liver damage and chronic inflammation. Several inflammatory response pathways, such as NF-κB and JAK/STAT3 signaling pathways, play roles in the crosstalk between inflammation and HCC. MicroRNAs (miRNAs) are evolutionarily conserved, short endogenous, non-coding single-stranded RNAs that are involved in various biological and pathological processes by regulating gene expression and protein translation. Evidence showed that miRNAs play a pivotal role in hepatitis virus infection and serve as promoters or inhibitors of inflammatory response. Aberrant miRNA was observed during liver inflammation and HCC. Many dysregulated miRNAs modulate the initiation and progression of inflammation-induced HCC. This review summarizes the role and functions of miRNAs in inflammation-associated HCC, as well as the designed therapeutics targeting miRNAs to treat liver inflammation and HCC.

Long noncoding RNA miR503HG, a prognostic indicator, inhibits tumor metastasis by regulating the HNRNPA2B1/NF-κB pathway in hepatocellular carcinoma

Long noncoding RNAs (lncRNAs) have been associated with hepatocellular carcinoma (HCC), but the underlying molecular mechanisms of their specific association with hepatocarcinogenesis have not been fully explored. Methods: miR503HG was identified by microarray and validated by real-time PCR. Survival analysis was evaluated using the Kaplan-Meier method and assessed using the log-rank test. In vitro and in vivo assays were preformed to explore the biological effects of miR503HG in HCC cells. The interaction of miR503HG with HNRNPA2B1 was identified by RNA pull-down and RNA immunoprecipitation. Expression of HNRNPA2B1 was examined by western blotting, immunofluorescence and immunohistochemical analyses, while HNRNPA2B1 ubiquitination was detected by immunoprecipitation. Results: We have identified 713 differentially expressed lncRNAs in 12 pairs of HCC tissues compared with corresponding noncancerous liver tissues. One of these lncRNAs, miR503HG, the host gene of miR503, is markedly decreased in HCC. Expression level of miR503HG is significantly associated with the time to recurrence and overall survival and is an independent risk factor for recurrence and survival. Enhanced expression of miR503HG could noticeably inhibit HCC invasion and metastasis in vitro and in vivo. Further investigation suggested that miR503HG could specifically interact with the heterogeneous nuclear ribonucleoprotein A2/B1 (HNRNPA2B1). miR503HG promoted HNRNPA2B1 degradation via the ubiquitin-proteasome pathway, which reduced the stability of p52 and p65 mRNA, and simultaneously suppressed the NF-κB signaling pathway in HCC cells. In addition, miR503HG can function synergistically with miR503 to inhibit HCC migration. Conclusion: Our findings support a role for miR503HG in tumor recurrence risk and survival prediction in HCC patients. We demonstrate a novel mechanism by which miR503HG inhibits the NF-κB signaling pathway and exerts its metastatic tumor suppression function through modulating the ubiquitination status of HNRNPA2B1.