Ji-hang Yuan

A Long Noncoding RNA Activated by TGF-β Promotes the Invasion-Metastasis Cascade in Hepatocellular Carcinoma

The role of TGF-β-induced epithelial-mesenchymal transition (EMT) in cancer cell dissemination is well established, but the involvement of lncRNAs in TGF-β signaling is still unknown. In this study, we observed that the lncRNA-activated by TGF-β (lncRNA-ATB) was upregulated in hepatocellular carcinoma (HCC) metastases and associated with poor prognosis. lncRNA-ATB upregulated ZEB1 and ZEB2 by competitively binding the miR-200 family and then induced EMT and invasion. In addition, lncRNA-ATB promoted organ colonization of disseminated tumor cells by binding IL-11 mRNA, autocrine induction of IL-11, and triggering STAT3 signaling. Globally, lncRNA-ATB promotes the invasion-metastasis cascade. Thus, these findings suggest that lncRNA-ATB, a mediator of TGF-β signaling, could predispose HCC patients to metastases and may serve as a potential target for antimetastatic therapies.

Long noncoding RNA high expression in hepatocellular carcinoma facilitates tumor growth through enhancer of zeste homolog 2 in humans

In recent years, long noncoding RNAs (lncRNAs) have been shown to have critical regulatory roles in cancer biology. However, the contributions of lncRNAs to hepatitis B virus (HBV)‐related hepatocellular carcinoma (HCC) remain largely unknown. Differentially expressed lncRNAs between HBV‐related HCC and paired peritumoral tissues were identified by microarray and validated using quantitative real‐time polymerase chain reaction. Liver samples from patients with HBV‐related HCC were analyzed for levels of a specific differentially expressed lncRNA High Expression In HCC (termed lncRNA‐HEIH); data were compared with survival data using the Kaplan‐Meier method and compared between groups by the log‐rank test. The effects of lncRNA‐HEIH were assessed by silencing and overexpressing the lncRNA in vitro and in vivo. The expression level of lncRNA‐HEIH in HBV‐related HCC is significantly associated with recurrence and is an independent prognostic factor for survival. We also found that lncRNA‐HEIH plays a key role in G0/G1 arrest, and further demonstrated that lncRNA‐HEIH was associated with enhancer of zeste homolog 2 (EZH2) and that this association was required for the repression of EZH2 target genes. Conclusions: Together, these results indicate that lncRNA‐HEIH is an oncogenic lncRNA that promotes tumor progression and leads us to propose that lncRNAs may serve as key regulatory hubs in HCC progression. (HEPATOLOGY 2011

Oncofetal long noncoding RNA PVT1 promotes proliferation and stem cell‐like property of hepatocellular carcinoma cells by stabilizing NOP2

Many protein‐coding oncofetal genes are highly expressed in murine and human fetal liver and silenced in adult liver. The protein products of these hepatic oncofetal genes have been used as clinical markers for the recurrence of hepatocellular carcinoma (HCC) and as therapeutic targets for HCC. Herein we examined the expression profiles of long noncoding RNAs (lncRNAs) found in fetal and adult liver in mice. Many fetal hepatic lncRNAs were identified; one of these, lncRNA‐mPvt1, is an oncofetal RNA that was found to promote cell proliferation, cell cycling, and the expression of stem cell‐like properties of murine cells. Interestingly, we found that human lncRNA‐hPVT1 was up‐regulated in HCC tissues and that patients with higher lncRNA‐hPVT1 expression had a poor clinical prognosis. The protumorigenic effects of lncRNA‐hPVT1 on cell proliferation, cell cycling, and stem cell‐like properties of HCC cells were confirmed both in vitro and in vivo by gain‐of‐function and loss‐of‐function experiments. Moreover, mRNA expression profile data showed that lncRNA‐hPVT1 up‐regulated a series of cell cycle genes in SMMC‐7721 cells. By RNA pulldown and mass spectrum experiments, we identified NOP2 as an RNA‐binding protein that binds to lncRNA‐hPVT1. We confirmed that lncRNA‐hPVT1 up‐regulated NOP2 by enhancing the stability of NOP2 proteins and that lncRNA‐hPVT1 function depends on the presence of NOP2. Conclusion: Our study demonstrates that the expression of many lncRNAs is up‐regulated in early liver development and that the fetal liver can be used to search for new diagnostic markers for HCC. LncRNA‐hPVT1 promotes cell proliferation, cell cycling, and the acquisition of stem cell‐like properties in HCC cells by stabilizing NOP2 protein. Regulation of the lncRNA‐hPVT1/NOP2 pathway may have beneficial effects on the treatment of HCC. (Hepatology 2014;60:1278–1290)

Long noncoding RNAs associated with liver regeneration 1 accelerates hepatocyte proliferation during liver regeneration by activating Wnt/β-catenin signaling.

In recent years, long noncoding RNAs (lncRNAs) have been investigated as a new class of regulators of biological function. A recent study reported that lncRNAs control cell proliferation in hepatocellular carcinoma (HCC). However, the role of lncRNAs in liver regeneration and the overall mechanisms remain largely unknown. To address this issue, we carried out a genome‐wide lncRNA microarray analysis during liver regeneration in mice after 2/3 partial hepatectomy (PH) at various timepoints. The results revealed differential expression of a subset of lncRNAs, notably a specific differentially expressed lncRNA associated with Wnt/β‐catenin signaling during liver regeneration (an lncRNA associated with liver regeneration, termed lncRNA‐LALR1). The functions of lncRNA‐LALR1 were assessed by silencing and overexpressing this lncRNA in vitro and in vivo. We found that lncRNA‐LALR1 enhanced hepatocyte proliferation by promoting progression of the cell cycle in vitro. Furthermore, we showed that lncRNA‐LALR1 accelerated mouse hepatocyte proliferation and cell cycle progression during liver regeneration in vivo. Mechanistically, we discovered that lncRNA‐LALR1 facilitated cyclin D1 expression through activation of Wnt/β‐catenin signaling by way of suppression of Axin1. In addition, lncRNA‐LALR1 inhibited the expression of Axin1 mainly by recruiting CTCF to the AXIN1 promoter region. We also identified a human ortholog RNA of lncRNA‐LALR1 (lncRNA‐hLALR1) and found that it was expressed in human liver tissues. Conclusion: lncRNA‐LALR1 promotes cell cycle progression and accelerates hepatocyte proliferation during liver regeneration by activating Wnt/β‐catenin signaling. Pharmacological intervention targeting lncRNA‐LALR1 may be therapeutically beneficial in liver failure and liver transplantation by inducing liver regeneration. (Hepatology 2013;58:739–751)

The histone deacetylase 4/SP1/microrna‐200a regulatory network contributes to aberrant histone acetylation in hepatocellular carcinoma

As an important epigenetic mechanism, histone acetylation modulates the transcription of many genes and plays important roles in hepatocellular carcinoma (HCC). Aberrations in histone acetylation have been observed in HCC, but the factors that contribute to the aberrations have not been fully elucidated. MicroRNAs (miRNAs), which are noncoding RNAs that regulate gene expression, are involved in important epigenetic mechanisms. In this study, we determined that miR‐200a and the level of histone H3 acetylation at its promoter were reduced in human HCC tissues in comparison with adjacent noncancerous hepatic tissues. Furthermore, our results suggested that the histone deacetylase 4 (HDAC4) inhibited the expression of miR‐200a and its promoter activity and reduced the histone H3 acetylation level at the mir‐200a promoter through a Sp1‐dependent pathway. Interestingly, we observed that the miR‐200a directly targeted the 3′‐untranslated region of the HDAC4 messenger RNA and repressed expression of HDAC4. Therefore, miR‐200a ultimately induced its own transcription and increased the histone H3 acetylation level at its own promoter. Through targeting HDAC4, miR‐200a also induced the up‐regulation of total acetyl‐histone H3 levels and increased the histone H3 acetylation level at the p21WAF/Cip1 promoter. Finally, we determined that miR‐200a inhibited the proliferation and migration of HCC cells in vivo and in vitro. Conclusion: Our findings suggest that the HDAC4/Sp1/miR‐200a regulatory network induces the down‐regulation of miR‐200a and the up‐regulation of HDAC4 in HCC. As a result, down‐regulation of miR‐200a enhances the proliferation and migration of HCC cells and induces aberrant histone acetylation in HCC. These findings highlight a potential therapeutic approach in targeting the HDAC4/Sp1/miR‐200a regulatory network for the treatment of HCC. (HEPATOLOGY 2011

Systemic genome screening identifies the outcome associated focal loss of long noncoding RNA PRAL in hepatocellular carcinoma

Systemic analyses using large‐scale genomic profiles have successfully identified cancer‐driving somatic copy number variations (SCNVs) loci. However, functions of vast focal SCNVs in “protein‐coding gene desert” regions are largely unknown. The integrative analysis of long noncoding RNA (lncRNA) expression profiles with SCNVs in hepatocellular carcinoma (HCC) led us to identify the recurrent deletion of lncRNA‐PRAL (p53 regulation‐associated lncRNA) on chromosome 17p13.1, whose genomic alterations were significantly associated with reduced survival of HCC patients. We found that lncRNA‐PRAL could inhibit HCC growth and induce apoptosis in vivo and in vitro through p53. Subsequent investigations indicated that the three stem‐loop motifs at the 5′ end of lncRNA‐PRAL facilitated the combination of HSP90 and p53 and thus competitively inhibited MDM2‐dependent p53 ubiquitination, resulting in enhanced p53 stability. Additionally, in vivo lncRNA‐PRAL delivery efficiently reduced intrinsic tumors, indicating its potential therapeutic application. Conclusions: lncRNA‐PRAL, one of the key cancer‐driving SCNVs, is a crucial stimulus for HCC growth and may serve as a potential target for antitumor therapy. (Hepatology 2016;63:850‐863)

METTL14 suppresses the metastatic potential of hepatocellular carcinoma by modulating N6‐methyladenosine‐dependent primary MicroRNA processing

N6‐Methyladenosine (m6A) modification has been implicated in many biological processes. However, its role in cancer has not been well studied. Here, we demonstrate that m6A modifications are decreased in hepatocellular carcinoma, especially in metastatic hepatocellular carcinoma, and that methyltransferase‐like 14 (METTL14) is the main factor involved in aberrant m6A modification. Moreover, METTL14 down‐regulation acts as an adverse prognosis factor for recurrence‐free survival of hepatocellular carcinoma and is significantly associated with tumor metastasis in vitro and in vivo. We confirm that METTL14 interacts with the microprocessor protein DGCR8 and positively modulates the primary microRNA 126 process in an m6A‐dependent manner. Further experiments show that microRNA 126 inhibits the repressing effect of METTL14 in tumor metastasis. Conclusion: These studies reveal an important role of METTL14 in tumor metastasis and provide a fresh view on m6A modification in tumor progression. (Hepatology 2017;65:529‐543).

The MBNL3 splicing factor promotes hepatocellular carcinoma by increasing PXN expression through the alternative splicing of lncRNA-PXN-AS1

Understanding the roles of splicing factors and splicing events during tumorigenesis would open new avenues for targeted therapies. Here we identify an oncofetal splicing factor, MBNL3, which promotes tumorigenesis and indicates poor prognosis of hepatocellular carcinoma patients. MBNL3 knockdown almost completely abolishes hepatocellular carcinoma tumorigenesis. Transcriptomic analysis revealed that MBNL3 induces lncRNA-PXN-AS1 exon 4 inclusion. The transcript lacking exon 4 binds to coding sequences of PXN mRNA, causes dissociation of translation elongation factors from PXN mRNA, and thereby inhibits PXN mRNA translation. In contrast, the transcript containing exon 4 preferentially binds to the 3′ untranslated region of PXN mRNA, protects PXN mRNA from microRNA-24–AGO2 complex-induced degradation, and thereby increases PXN expression. Through inducing exon 4 inclusion, MBNL3 upregulates PXN, which mediates the pro-tumorigenic roles of MBNL3. Collectively, these data demonstrate detailed mechanistic links between an oncofetal splicing factor, a splicing event and tumorigenesis, and establish splicing factors and splicing events as potential therapeutic targets.

Long noncoding RNA MRCCAT1 promotes metastasis of clear cell renal cell carcinoma via inhibiting NPR3 and activating p38-MAPK signaling

BackgroundRecent evidences showed that long noncoding RNAs (lncRNAs) are frequently dysregulated and play important roles in various cancers. Clear cell renal cell carcinoma (ccRCC) is one of the leading cause of cancer-related death, largely due to the metastasis of ccRCC. However, the clinical significances and roles of lncRNAs in metastatic ccRCC are still unknown.MethodslncRNA expression microarray analysis was performed to search the dysregulated lncRNA in metastatic ccRCC. quantitative real-time PCR was performed to measure the expression of lncRNAs in human ccRCC samples. Gain-of-function and loss-of-function experiments were performed to investigate the biological roles of lncRNAs on ccRCC cell proliferation, migration, invasion and in vivo metastasis. RNA pull-down, RNA immunoprecipitation, chromatin immunoprecipitation, and western blot were performed to explore the molecular mechanisms underlying the functions of lncRNAs.ResultsThe microarray analysis identified a novel lncRNA termed metastatic renal cell carcinoma-associated transcript 1 (MRCCAT1), which is highly expressed in metastatic ccRCC tissues and associated with the metastatic properties of ccRCC. Multivariate Cox regression analysis revealed that MRCCAT1 is an independent prognostic factor for ccRCC patients. Overexpression of MRCCAT1 promotes ccRCC cells proliferation, migration, and invasion. Depletion of MRCCAT1 inhibites ccRCC cells proliferation, migration, and invasion in vitro, and ccRCC metastasis in vivo. Mechanistically, MRCCAT1 represses NPR3 transcription by recruiting PRC2 to NPR3 promoter, and subsequently activates p38-MAPK signaling pathway.ConclusionsMRCCAT1 is a critical lncRNA that promotes ccRCC metastasis via inhibiting NPR3 and activating p38-MAPK signaling. Our results imply that MRCCAT1 could serve as a prognostic biomarker and therapeutic target for ccRCC.

Long noncoding RNA H19 inhibits the proliferation of fetal liver cells and the Wnt signaling pathway

In this study, we found that H19 is the most strongly differentially expressed long noncoding RNA (lncRNA) during liver development. H19 may inhibit the proliferation of fetal liver cells by blocking the interaction between heterogeneous nuclear ribonucleoprotein (hnRNP) U and actin, which results in gene transcriptional repression. Based on ChIP‐seq analysis, we found that genes involved in the Wnt signaling pathway are enriched among hnRNP U‐binding genes. Further investigation demonstrated that hnRNP U has opposing effects on cell proliferation and Wnt/β‐catenin signaling pathway activity compared to H19 and that hnRNP U is very important in this process.