Suppression Of Hepatocellular Carcinoma Research Articles

Potential Role of microRNA-183 as a Tumor Suppressor in Hepatocellular Carcinoma

Background/Aims: Disseminated tumors, known as metastases, are responsible for ninety-percent of mortality due to cancer. Epithelial to mesenchymal transition, a phenomenon required for morphological conversion of non-motile discoid shaped epithelial cells to highly motile spindle-shaped mesenchymal cells, is thought to be a pre-requisite for metastatic progression. Metastasis-associated 1 (MTA1) protein is a prime inducer of EMT and metastatic progression in all solid tumors including hepatocellular carcinoma (HCC). However, the molecular mechanisms that regulate the expression and function of MTA1 in HCC have not been elucidated. Methods: In silico prediction algorithms were used to find microRNAs (miRNAs) that may target MTA1. We examined the relationship between the expression of MTA1 and miR-183 using quantitative real time PCR. We also determined the levels of the MTA1 protein using immunohistochemistry. Reporter assays, in the presence and absence of the miR-183 mimic, were used to confirm MTA1 as a bona fide target of miR183. The effect of miR-183 on HCC pathogenesis was determined using a combination of in vitro migration and invasion assay, together with in vivo xenograft experiments. The correlation between miR-183 and MTA1 expression was also studied in samples from HCC patients, and in The Cancer Genome Atlas dataset. Results: Analysis of the sequence database revealed that MTA1 is a putative target of miR-183. MTA1 protein and RNA expression showed opposite trends to miR-183 expression in breast, renal, prostate, and testicular tissue samples from cancer patients, and in the metastatic HCC cell line HepG2. An inverse correlation was also observed between MTA1 (high) and miR-183 (low) expression within samples from HHC patients and in the TCGA dataset. Reporter assays in HepG2 cells showed that miR-183 could inhibit translation of a reporter harboring the wild-type, but not the mutant miR-183 3’-untranslated region (UTR). In addition, miR-183 significantly inhibited in vitro migration and invasion in HepG2 cells, and in vivo hepatic metastasis. Conclusion: Our results reveal a novel post-transcriptional regulatory mechanism for MTA1 expression via miR-183, which is suppressed during HCC pathogenesis.

Integrin α9 Suppresses Hepatocellular Carcinoma Metastasis by Rho GTPase Signaling.

Integrin subunit alpha 9 (ITGA9) mediates cell-cell and cell-matrix adhesion, cell migration, and invasion through binding different kinds of extracellular matrix (ECM) components. However, its potential role and underlying molecular mechanisms remain unclear in hepatocellular carcinoma (HCC). Here, we found that ITGA9 expression was obviously decreased in patients with HCC, which was negatively correlated with HCC growth and metastasis. ITGA9 overexpression significantly inhibited cell proliferation and migration in vitro as well as tumor growth and metastasis in vivo. Our data demonstrated that the inhibitory effect of ITGA9 on HCC cell motility was associated with reduced phosphorylation of focal adhesion kinase (FAK) and c-Src tyrosine kinase (Src), disrupted focal adhesion reorganization, and decreased Rac1 and RhoA activity. Our data suggest ITGA9, as a suppressor of HCC, prevents tumor cell migration and invasiveness through FAK/Src-Rac1/RhoA signaling.

Utility of miR‑133a‑3p as a diagnostic indicator for hepatocellular carcinoma: An investigation combined with GEO, TCGA, meta‑analysis and bioinformatics.

Increasing evidence has demonstrated that microRNA (miR)-133a-3p is an important regulator of hepatocellular carcinoma (HCC). In the present study, the diagnostic role of miR-133a-3p in HCC, and the potential functional pathways, were both explored based on publicly available data. Eligible microarray datasets were collected from NCBI Gene Expression Omnibus (GEO) database and ArrayExpress database. The data related to HCC and matched adjacent normal tissues were also downloaded from The Cancer Genome Atlas (TCGA). Published studies reporting the association between miR-133a-3p expression and HCC were reviewed from multiple databases. By combining the data derived from three sources (GEO, TCGA and published studies), the authors analyzed the comprehensive relationship between miR-133a-3p expression and clinicopathological features of HCC. Eventually, putative targets of miR-133a-3p in HCC were selected for further bioinformatics prediction. A total of eight published microarray datasets were gathered, and the pooled results demonstrated that the expression of miR-133a-3p in the tumor group was lower than that in normal groups [standardized mean difference (SMD)=−0.54; 95% confidence interval (CI), −0.74 to −0.35; P<0.001]. Consistently, the level of miR-133a-1 in HCC was reduced markedly compared to normal tissues (P<0.001) based on TCGA data, and the AUC value of low miR-133a-1 expression for HCC diagnosis was 0.670 (P<0.001). Furthermore, the combined SMD of all datasets (GEO, TCGA and literature) suggested that significant difference was observed between the HCC group and the normal control group, and lower miR-133a-3p expression in HCC group was noted (SMD=−0.69; 95% CI, −1.10 to −0.29; P=0.001). In addition, the authors discovered five key genes of the calcium signaling pathway (NOS1, ADRA1A, ADRA1B, ADRA1D and TBXA2R) that may probably be targeted by miR-133a-3p in HCC. The study reveals that miR-133a-3p may function as a tumor suppressor in HCC. The prospective novel pathways and key genes of miR-133a-3p could offer potential biomarkers for HCC; however, the predictions require further confirmation.

Clinical significance of CMTM4 expression in hepatocellular carcinoma.

CMTM4 is the most conserved member of chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing (CMTM) family on chromosome 16q22.1, a locus that harbors a number of tumor-suppressor genes. In previous studies, CMTM4 was reported to be downregulated and exhibited tumor-suppressor activities by regulating cell growth and cell cycle in clear cell renal cell carcinoma. However, its roles in tumorigenesis of hepatocellular carcinoma (HCC) remain poorly studied. This study first investigated the expression of CMTM4 in HCC, and then examined the association between the expression of CMTM4 with the clinicopathological features and prognosis of HCC patients. It was found that CMTM4 was downregulated in HCC tissues, compared with matched adjacent nontumor tissues, as detected by immunohistochemistry. In addition, Kaplan–Meier survival analysis showed that the negative expression of CMTM4 was associated with decreased overall survival rates in patients with HCC. The results of this study suggest CMTM4 plays a role as a tumor suppressor in HCC and CMTM4 negative expression is a risk factor for poor prognosis of HCC.

IFI16 restoration in hepatocellular carcinoma induces tumour inhibition via activation of p53 signals and inflammasome.

Interferon-inducible 16 (IFI16) is known to involve in p53-dependent tumour suppression and also the formation of inflammasome, which function, however, remains controversy during carcinogenesis as a pattern recognition receptor for tumour death-derived free DNA. In this study, we investigated the anti-tumour role of IFI16 in hepatocellular carcinoma (HCC). Hepatocellular carcinoma tissues (n=20) and corresponding non-neoplastic tissues (n=20) were collected to determine the expression of IFI16. After the transfection of pcDNA3.1-IFI16 into Huh7 and SMMC7721 cells in vitro, the influence of IFI16 overexpression on cell vitality, colony formation, apoptosis and migration were analysed. The role effect of IFI16 in vivo was further investigated. The expression of IFI16 was significantly decreased in tumour tissues and cell lines. Overexpression of IFI16 induced decrease of cell vitality, colony formation and increased apoptosis with impaired ability of migration. Mechanistically, IFI16 could activate p53 at Ser15 to up-regulate the p21WAF1/CIP1 level to inhibit tumour growth and migration, which was restored by the p53 inhibitor Pifithrin-α (20μmol/L). Moreover, IFI16-induced tumour cell death promoted the recruitment of inflammasome complex to enhance tumour inhibition, but the caspase-1 inhibitor Ac-YVAD-CMK (50μmol/L) could suppress this process in HCC. The results in vivo indicated that restored expression of IFI16 in tumour cells effectively promote tumour regression, which could be partly abrogated by the inhibition of activation of p53 signals or induced inflammasome. IFI16 is a tumour suppressor in HCC via activation of p53 signals and inflammasome.

Metformin and insulin impact on clinical outcome in patients with advanced hepatocellular carcinoma receiving sorafenib: Validation study and biological rationale

PurposeIn 2015, we published a study on a small series of patients with hepatocellular carcinoma (HCC) treated chronically with metformin for type II diabetes mellitus (DM2) who showed a poorer response to sorafenib. The aim of the present study was to validate the prognostic significance of metformin in HCC patients treated with sorafenib, providing a biological rationale for the mechanism of resistance to sorafenib in patients on chronic metformin therapy, and to clarify the role of sirtuin-3 (SIRT-3), a protein involved in metabolic diseases and acknowledged as a tumour suppressor in HCC, in this resistance. Patients and methodsWe analysed 279 patients consecutively treated with sorafenib for the clinical analysis. Of the 86 (30%) patients with DM2, 52 (19%) were on chronic treatment with metformin and 34 (12%) with insulin. We included 43 patients with HCC for the biological study: 19 (44.1%) were diabetic and 14 (73.7%) of these received metformin for DM2. SIRT-3 expression was investigated by immunohistochemistry (IHC) in formalin-fixed and paraffin-embedded (FFPE) samples. ResultsIn HCC patients undergoing chronic treatment with metformin, the use of sorafenib was associated with poor progression-free survival (PFS) and overall survival (OS) (1.9 and 6.6 months, respectively) compared to 3.7 months and 10.8 months, respectively, for patients without DM2 and 8.4 months and 16.6 months, respectively, for patients on insulin (P < .0001). We also observed that SIRT-3 protein expression was significantly higher in patients treated with metformin than in those not taking this medication (65% versus 25%, respectively) (P = .013). ConclusionsOur findings could be attributed to increased tumour aggressiveness and resistance to sorafenib caused by chronic treatment with metformin.

Abstract 5328: RNF12 inhibits the proliferation of hepatocellular carcinoma through c-Myc and p21

Abstract Purpose: RNF12/RLIM, a RING E3 ubiquitin ligase, plays an important role in the epigenetic regulation of sex-specific nurturing tissues in female mice. Recently, a few studies demonstrated a correlation between RNF12 and the proliferation of multiple cancers. The role of RNF12 in hepatocellular carcinoma is incompletely understood. The purpose of this study is to investigate the effect of RNF12 on the proliferation of human hepatocellular carcinoma cells. RNF12 is also known to interact with a number of nuclear proteins, including CLIM, HDAC2, and Smad4. We also explored whether c-Myc and p21, an oncogene and tumor suppressor essential to liver tumorigenesis, were affected by RNF12. Methods: Immunohistochemistry of RNF12 and c-Myc was performed on surgically dissected human hepatocellular carcinoma tissues. The soft-agar cloning, flow cytometry and Transwell invasion assays were carried out to investigate the role of RNF12 in SK-Hep1 cell proliferation, cell cycle and invasiveness. Real-time quantitative PCR and Western blotting were used to examine the mRNA and protein levels of RNF12 and related proteins in SK-Hep1 cells. Results: We found that the level of RNF12 was lower in hepatocellular carcinoma, compared with the surrounding non-cancerous tissues, while the c-Myc expression was higher. Using a SK-Hep1 cell line stably expressing RNF12, we showed that RNF12 over-expression inhibited cell proliferation and induced cell cycle arrest at G1 phase. Furthermore, we showed that RNF12 over-expression decreased the level of oncoprotein c-Myc, while not much affecting its mRNA level. Co-immunoprecipitation demonstrated that RNF12 and c-Myc associated with each other, suggesting a direct protein-protein interaction. RNF12 over-expression also markedly increased the mRNA and protein levels of p21, a tumor suppressor and the downstream target of p53, c-Myc and many other cancer-related regulators. Consistently, silencing of RNF12 reduced p21 mRNA and protein levels and increased c-Myc protein. Conclusion: Our study demonstrated reduced expression of RNF12 in hepatocellular carcinoma, and RNF12 over-expression inhibited the proliferation and cell cycle progression of SK-Hep1 cells. Mechanistically, RNF12 may directly regulate the level of c-Myc, similarly as other transcription factors such as CLIM and Smad4. The mechanisms underlying the increased expression of p21 is being investigated. Taken together, RNF12 may serve as a tumor suppressor in hepatocellular carcinoma, partly through oncoprotein c-Myc and tumor suppressor p21. Note: This abstract was not presented at the meeting. Citation Format: Meng Nie, Yongsheng Huang, Lin Wang. RNF12 inhibits the proliferation of hepatocellular carcinoma through c-Myc and p21 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5328. doi:10.1158/1538-7445.AM2017-5328

Abstract 4984: BNip3 suppresses hepatocellular carcinoma (HCC) growth by limiting lipogenesis

Abstract BNip3 is a mitochondrial protein that promotes the turnover of mitochondria at the autophagolysosome when nutrient supplies are low. BNip3-null livers exhibit lipid accumulation and develop a phenotype mimicking non-alcoholic steatohepatitis, a known precursor for development of hepatocellular carcinoma (HCC). Additionally, BNip3 is silenced in human HCC and other malignancies and this loss often correlates with more aggressive tumors and worse outcomes. However, the functional significance of BNIP3 loss for growth and progression of HCC has not been determined. We utilized the diethylnitrosamine (DEN)-induced mouse model of HCC to determine how loss of BNip3 affected HCC development in the mouse. Wild type and BNip3-null mice were treated with DEN, and tumor burden (size and number) was assessed at 6, 8, and 10 months of age. We also generated primary HCC cell lines from the tumors arising in BNip3-null mice for in vitro analysis of tumor cell growth and metabolism. We observed that BNip3-null mice had reduced tumor latency and enhanced tumor growth rate in the liver following DEN treatment compared to wild type mice consistent with BNip3 functioning as a tumor suppressor of HCC. Interestingly, tumors arising in BNip3-null mice accumulated increased lipid and qPCR analysis of primary tumors and cell lines revealed increased expression of lipogenesis genes compared to wild type. Treatment with a novel fatty acid synthase inhibitor or re-expression of BNip3 in the BNip3-null HCC cell lines reduced tumor cell growth and lipogenesis, and promoted oxidative metabolism. These results indicate that BNip3 acts as a tumor suppressor in HCC by limiting de novo lipogenesis and suggest that fatty acid synthase inhibitors could be effective therapeutically against BNIP3 deficient HCC in patients. Citation Format: Kay F. Macleod. BNip3 suppresses hepatocellular carcinoma (HCC) growth by limiting lipogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4984. doi:10.1158/1538-7445.AM2017-4984

TNFSF9 exerts an inhibitory effect on hepatocellular carcinoma.

Tumor necrosis factor superfamily member 9 (TNFSF9), also known as 4-1BBL and CD137L, has been implicated in cancer immunotherapy due to its function as a T-cell co-stimulator. We aimed to investigate the role of TNFSF9 in the cancer pathogenesis in hepatocellular carcinoma (HCC). TNFSF9 expression was examined by immunohistochemistry in 106 pairs of HCC and adjacent non-tumorous tissues, and by quantitative polymerase chain reaction and Western blot in HCC cell lines. The impact of TNFSF9 on the proliferation, migration and invasion of HCC cells was determined using the 3-(4,5-diethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) and transwell assays in vitro. We also assessed the influence of TNFSF9 on the growth and metastasis of HCC tumors in an orthotopic mouse model of human HCC. TNFSF9 expression was downregulated in approximately 70% of HCC tissues. A decreased expression of TNFSF9 was also consistently observed in all the four HCC cell lines. Either the overexpression of TNFSF9 or treatment with recombinant TNFSF9 protein could significantly inhibit the proliferation, migration and invasion of Huh7 and SMMC-7721 HCC cells in vitro. The inhibitory effect of TNFSF9 on HCC was further confirmed in vivo. Mice orthotopically transplanted with TNFSF9-overexpressing Huh7 cells developed significantly smaller tumors with less intrahepatic metastasis and distant metastasis compared with the control group. TNFSF9 may be a tumor suppressor in HCC. Based on its immune stimulatory aspect and the tumor inhibition property, TNFSF9 may be a promising therapeutic target for HCC.

MiRNA-708 functions as a tumour suppressor in hepatocellular carcinoma by targeting SMAD3

Hepatocellular carcinoma (HCC) is the most frequent subtype of primary liver cancer and the third most common cause of cancer-associated mortality worldwide. Previous studies have reported that microRNAs (miRNAs) serve key roles in the carcinogenesis and progression of HCC by regulating gene expression. The present study investigated the expression patterns, biological roles and underlying mechanisms of miRNA-708 (miR-708) in HCC. The expression levels of miR-708 in HCC tissue samples and cell lines were examined. Cell proliferation, migration and invasion assays were used to evaluate the effect of miR-708 on HCC cells. In addition, bioinformatic and western blotting analyses, and dual luciferase reporter assays were performed to investigate the direct gene target of miR-708. The results of the present study demonstrated that miR-708 expression was significantly decreased in HCC tissue samples and cell lines. In addition, the expression level of miR-708 was associated with increased HCC tumour stage. Furthermore, ectopic expression of miR-708 suppressed HCC cell proliferation, migration and invasion. The results of the present study also indicated that miR-708 targets SMAD family member 3 directly in vitro. The results of the present study indicated that miR-708 may be a novel target for future HCC therapy.

MiR-375 delivered by lipid-coated doxorubicin-calcium carbonate nanoparticles overcomes chemoresistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent and lethal disease that is characterized by drug resistance. Doxorubicin (DOX) is a widely used chemotherapeutic drug and miR-375 has been shown to be a tumor suppressor in HCC. Here, we reported that miR-375 and DOX co-loaded into lipid-coated calcium carbonate nanoparticles (LCC-DOX/miR-375 NPs), enhanced the anti-tumor effects through combination therapy, and were highly effective in reversing drug resistance in HCC. LCC-DOX/miR-375 NPs were prepared by a reverse microemulsions method. In vitro, LCC-DOX/miR-375 NPs exhibited enhanced intracellular accumulation, pH-sensitive DOX release and potent cytotoxicity. In vivo, LCC-DOX/miR-375 NPs showed efficient antitumor effect both in xenograft and primary HCC murine models. Our results showed that the LCC-DOX/miR-375 nanoparticles provide a novel strategy to overcome the drug resistance and promote addictive effect between miR-375 and DOX in HCC.

Downregulation of Talin1 promotes hepatocellular carcinoma progression through activation of the ERK1/2 pathway.

Talin1 is an adaptor protein that conjugates integrins to the cytoskeleton and regulates integrins and focal adhesion signaling. Several studies have found that Talin1 is overexpressed in several tumor types and promotes tumor progression. However, the explicit role of Talin1 in hepatocellular carcinoma (HCC) progression is still unclear and its functional mechanism remains largely unknown. In this study, we showed a trend of gradually decreasing expression of Talin1 from normal liver tissues to hepatocirrhosis, liver hyperplasia, the corresponding adjacent non‐tumor, primary HCC, and eventually metastatic foci, indicating that Talin1 may correlate with HCC initiation to progression. Talin1 was significantly downregulated in HCC tissues compared with adjacent non‐tumor tissues and low Talin1 expression was associated with HCC progression and poor prognosis. Furthermore, Talin1 knockdown induced epithelial–mesenchymal transition and promoted migration and invasion in SK‐Hep‐1 cells and HepG2 cells. Mechanistically, we found that the ERK pathway was responsible for these promoting effects of Talin1 knockdown in HCC cells. The promoting effects of Talin1 knockdown on epithelial–mesenchymal transition, migration, and invasion were reversed by U0126, a specific ERK1/2 inhibitor. Taken together, our results suggested that Talin1 might serve as a tumor suppressor in HCC and a potential prognostic biomarker for HCC patients.

Peroxisome proliferator-activated receptor gamma coactivator-1 alpha acts as a tumor suppressor in hepatocellular carcinoma.

Peroxisome proliferator-activated receptor gamma coactivator-1 alpha plays a crucial role in regulating the biosynthesis of mitochondria, which is closely linked to the energy metabolism in various tumors. This study investigated the regulatory role of peroxisome proliferator-activated receptor gamma coactivator-1 alpha in the pathogenesis of hepatocellular carcinoma. In this study, the changes of peroxisome proliferator-activated receptor gamma coactivator-1 alpha messenger RNA levels between normal human liver and hepatocellular carcinoma tissue were examined by quantitative reverse transcription polymerase chain reaction. Knockdown of peroxisome proliferator-activated receptor gamma coactivator-1 alpha was conducted by RNA interference in the human liver cell line L02, while overexpression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha was conducted by adenovirus encoding peroxisome proliferator-activated receptor gamma coactivator-1 alpha complementary DNA in the human hepatocarcinoma cell line HepG2. Cellular morphological changes were observed via optical and electron microscopy. Cellular apoptosis was determined by Hoechst 33258 staining. In addition, the expression levels of 21,400 genes in tissues and cells were detected by microarray. It was shown that peroxisome proliferator-activated receptor gamma coactivator-1 alpha expression was significantly downregulated in hepatocellular carcinoma compared with normal liver tissues. After knockdown of peroxisome proliferator-activated receptor gamma coactivator-1 alpha expression in L02 cells, cells reverted to immature and dedifferentiated morphology exhibiting cancerous tendency. Apoptosis occurred in the HepG2 cells after transfection by adenovirus encoding peroxisome proliferator-activated receptor gamma coactivator-1 alpha. Microarray analysis showed consistent results. The results suggest that peroxisome proliferator-activated receptor gamma coactivator-1 alpha acts as a tumor suppressor in the formation and development of hepatocellular carcinoma and that peroxisome proliferator-activated receptor gamma coactivator-1 alpha may be a potential therapeutic target for hepatocellular carcinoma.

MAGE-TRIM28 complex promotes the Warburg effect and hepatocellular carcinoma progression by targeting FBP1 for degradation

Hepatocellular carcinoma (HCC) is one of the leading cause of cancer death in the world. Fructose-1,6-biphosphatase (FBP1), a rate-limiting enzyme in gluconeogenesis, has been identified recently as a tumor suppressor in HCC and other cancer types. In this study, we demonstrated that the tripartite motif-containing protein 28 (TRIM28) binds directly to and promotes FBP1 for ubiquitination and degradation. MAGE-A3 and MAGE-C2, which are known to be overexpressed in HCC, can enhance TRIM28-dependent degradation of FBP1 by forming ubiquitin ligase complexes with TRIM28. We further showed that expression of TRIM28 increased glucose consumption and lactate production by promoting FBP1 degradation in HCC cells and that FBP1 is a key mediator of TRIM28-induced HCC growth in culture and in mice. Moreover, we demonstrated that FBP1 and TRIM28 protein levels inversely correlated in HCC patient specimens. Finally, we showed that the proteasome inhibitor bortezomib mitigated the Warburg effect by inhibiting FBP1 degradation in HCC. Collectively, our findings not only identify oncogenic MAGE-TRIM28 complex-mediated proteasome degradation of FBP1 as a key mechanism underlying downregulation of FBP1 proteins in HCC, but also reveal that MAGE-TRIM28-regulated reprogramming of cancer cell metabolism and HCC tumorigenesis is mediated, at least in part, through FBP1 degradation.

Hepatic cyclooxygenase-2 overexpression induced spontaneous hepatocellular carcinoma formation in mice

Cyclooxygenase (COX)-2 is upregulated in hepatocellular carcinoma (HCC). However, the direct causative effect of COX-2 in spontaneous HCC formation remains unknown. We thus investigate the role and molecular pathogenesis of COX-2 in HCC by using liver-specific COX-2 transgenic (TG) mice. We found spontaneous HCC formation with elevated inflammatory infiltrates and neovessels in male TG mice (3/21, 14.3%), but not in any of male WT mice (0/19). Reduced representation bisulfite sequencing (RRBS) and gene expression microarrays were performed in the HCC tumor and non-HCC liver tissues to investigate the molecular mechanisms of COX-2-driven HCC. By RRBS, DNA promoter hypermethylation was identified in HCC from TG mice. Induction of promoter hypermethylation was associated with reduced tet methylcytosine dioxygenase 1 (TET1) expression by COX-2. TET1 could catalyze the conversion of 5-methylcytosine into 5-hydroxymethylcytosine (5hmC) and prevents DNA hypermethylation. In keeping with this, loss of 5hmC was demonstrated in COX-2-induced HCC. Consistently, COX-2 overexpression in human HCC cell lines could reduce both TET1 expression and 5hmc levels. Integrative analyses of DNA methylation and gene expression profiles further identified significantly downregulated genes including LTBP1, ADCY5 and PRKCZ by promoter methylation in COX-2-induced HCC. Reduced expression of LTBP1, ADCY5 and PRKCZ by promoter hypermethylation was further validated in human HCCs. Bio-functional investigation revealed that LTBP1 inhibited cell proliferation in HCC cell lines, suggesting its potential role as a tumor suppressor in HCC. Gene expression microarrays revealed that signaling cascades (AKT (protein kinase B), STK33 (Serine/Threonine kinase 33) and MTOR (mechanistic target of rapamycin) pathways) were enriched in COX-2-induced HCC. In conclusion, this study demonstrated for the first time that enhanced COX-2 expression in hepatocytes is sufficient to induce HCC through inducing promoter hypermethylation by reducing TET1, silencing tumor-suppressive genes and activating key oncogenic pathways. Inhibition of COX-2 represents a mechanism-based target for HCC prevention.

Decreased expression of LncRNA SRA1 in hepatocellular carcinoma and its clinical significance

Hepatocellular carcinoma (HCC), is an extremely aggressive malignancy with poor prognosis and high fatality rates worldwide. Accumulating evidence indicated that novel biomarkers are required to get a better understanding of the biological mechanisms of HCC. SRA1, a long non-coding RNA (lncRNA), serves as a critical regulator in several cancers. However, the association between SRA1 expression and tumorigenesis in HCC tissues remains unclear. In the present study, we evaluated the expression of SRA1 in HCC and its clinical association. The expression levels of SRA1 in 67 pairs of cancer tissues and adjacent normal tissues from HCC patients were detected using quantitative real-time PCR. Expression of SRA1 in HCC cell lines compared with normal human hepatocyte cell lines was also measured. Finally, the potential associations between its level in HCC tissues and the clinicopathological parameters were analyzed as well. The results indicated that the expression levels of SRA1 in HCC were remarkably decreased, compared with matched normal tissues (P< 0.001). Levels of SRA1 in HCC cell lines were also significantly decreased than that in normal human hepatocyte cell line L-02. Additionally, the levels of SRA1 were significantly associated with tumor size (P= 0.020) and serum GLU level (P= 0.046). This study highlighted that SRA1 was downregulated in HCC and might serve as a tumor suppressor in HCC, which laid a solid foundation for future research.

HBx represses RIZ1 expression by DNA methyltransferase1 involvement in decreased miR-152 in hepatocellular carcinoma.

HepatitisB virus (HBV) is mainly suspected to promote hepatocellular carcinoma (HCC) development by epigenetic alteration. The HBV X protein (HBx) plays a key role in the molecular pathogenesis of HBV-related HCC. However, the mechanism of HBx-mediated hepatocarcinogenesis remains to be elucidated. RIZ1 gene, a candidate HCC suppressor gene, is frequently found to be hypermethylated and downregulated in HCC. In the present study, we show that the expression of RIZ1 was downregulated in 65% HCC tissues. Decreased expression of RIZ1 was restored by 5'-Aza in MHCC-97H HCC cell lines. HBx recombinant transfection increased DNMT1 expression level and suppressed RIZ1 expression. Moreover, knockdown of DNMT1 by siRNA restored RIZ1 expression in HCC cell SMMC-7721 and reduced methylated CpG sites of RIZ1. ChIP results showed that DNMT1 protein could bind to RIZ1 promoter, and this interaction was further enhanced with the transfected HBX recombinant. Moreover, miR-152 was decreased and involved in upregulation of DNMT1 in HBx transfected cells, at least partly, contributed to the epigenetic inactivation of RIZ1. Taken together, our data found that HBx repressed RIZ1 expression via DNMT1, which offered a new mechanism of RIZ1 inactivation in HCC, except for the widely known DNA methylation. These results enriched the epigenetic mechanism by which HBx contributes to pathogenesis of HBV-HCC.

The expression of a tumor suppressor gene JDP2 and its prognostic value in hepatocellular carcinoma patients

The c-Jun dimerization protein 2 (JDP2) belongs to the activator protein-1 (AP-1) family and functions as a repressor of the AP-1 complex by dimerizing with other c-Jun proteins. Thus, JDP2 plays an important role in the repression of AP-1-driven biological processes, such as differentiation and proliferation. Recent studies have suggested that JDP2 may function as a tumor suppressor through its suppressive action against the AP-1 complex, which is known to drive oncogenic signals in several human malignancies. In this study, we used immunohistochemistry to examine the JDP2 expression in 211 cases of hepatocellular carcinoma (HCC) and analyzed the potential link of JDP2 expression to the clinicopathological features of HCC patients. Clinical parameter analysis showed that high expression of JDP2 was significantly correlated with smaller tumor size (P=.002) and early stage HCC (P=.039). Moreover, Kaplan-Meier survival analysis showed that high expression of JDP2 was significantly associated with better survival in HCC patients (P=.006). Taken together, our results showed that JDP2 may serve as a tumor suppressor in HCC and could therefore serve as a good prognostic marker for patients with HCC.

SIRT3 functions as a tumor suppressor in hepatocellular carcinoma.

Hepatocellular carcinoma is one of the leading causes for cancer-related mortality worldwide. SIRT3 may function as either oncogene or tumor suppressor in a panel of cancers; however, the role of SIRT3 in hepatocellular carcinoma remains unclear. In this study, we assayed the expression level of SIRT3 in hepatocellular carcinoma tissues by quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry. A loss-of-function approach was used to examine the effects of SIRT3 on biological activity, including cell proliferative activity and invasive potential. The results demonstrated that the expression levels of SIRT3 protein in hepatocellular carcinoma tissues were significantly downregulated compared with those in adjacent non-cancerous tissues. Furthermore, SIRT3 could decrease cell proliferation and inhibit cell migration/invasion in hepatocellular carcinoma cell line. Taken together, these results elucidated the function of SIRT3 in hepatocellular carcinoma development and suggested that SIRT3 might function as tumor suppressor in hepatocellular carcinoma by targeting PI3K/Akt pathway.

MiR-199a-5p suppresses tumorigenesis by targeting clathrin heavy chain in hepatocellular carcinoma.

The deregulation of microRNA (miRNA) is frequently associated with a variety of cancers, including hepatocellular carcinoma (HCC). In this study, we investigated the expression and possible role of miR-199a-5p in HCC. The expression of miR-199a-5p was measured by quantitative RT-PCR in HCC. The effect of miR-199a-5p was evaluated by cell viability and colony formation assays in HCC cell lines and tumor cell growth assay in xenograft nude mice. Quantitative real time PCR results showed that miR-199a-5p was down-regulated in 77.9 % (67/86) of HCC tissues compared with adjacent nontumor tissues. MiR-199a-5p mimic reduced cell viability and colony formation by induction of cell arrest in HCC cell lines and inhibited tumor cell growth in xenograft nude mice, but miR-199a-5p inhibitor increased cell viability and colony formation in HCC cell lines and tumor cell growth in xenograft nude mice. Furthermore, CLTC was defined as a potential direct target of miR-199a-5p by MiRanda and TargetScan predictions. The dual-luciferase reporter gene assay results showed that CLTC was a direct target of miR-199a-5p. The use of miR-199a-5p mimic or inhibitor could decrease or increase CLTC protein levels in HCC cell lines. We conclude that the frequently down-regulated miR-199a-5p can regulate CLTC and might function as a tumor suppressor in HCC. Therefore, miR-199a-5p may serve as a useful therapeutic agent for miRNA-based HCC therapy.