Ji-Hua Ren

SIRT2 overexpression in hepatocellular carcinoma mediates epithelial to mesenchymal transition by protein kinase B/glycogen synthase kinase-3β/β-catenin signaling†‡

Sirtuin 1 (SIRT1) has been implicated in telomere maintenance and the growth of hepatocellular carcinoma (HCC). Nevertheless, the role of other sirtuins in the pathogenesis of HCC remains elusive. We found that sirtuin 2 (SIRT2), another member of the sirtuin family, also contributes to cell motility and invasiveness of HCC. SIRT2 is up‐regulated in HCC cell lines and in a subset of human HCC tissues (23/45). Up‐regulations of SIRT2 in primary HCC tumors were significantly correlated with the presence of microscopic vascular invasion (P = 0.001), a more advanced tumor stage (P = 0.004), and shorter overall survival (P = 0.0499). Functional studies by short hairpin RNA–mediated suppression of SIRT2 expression in HCC cell lines revealed significant inhibition of motility and invasiveness. Depletion of SIRT2 also led to the regression of epithelial‐mesenchymal transition (EMT) phenotypes, whereas the ectopic expression of SIRT2 in the immortalized hepatocyte cell line L02 promoted cell motility and invasiveness. Mechanistic studies revealed that SIRT2 regulates the deacetylation and activation of protein kinase B, which subsequently impinges on the glycogen synthase kinase‐3β/β‐catenin signaling pathway to regulate EMT. Conclusions: Our findings have uncovered a novel role for SIRT2 in HCC metastasis, and provide a rationale to explore the use of sirtuin inhibitors in HCC therapy. (HEPATOLOGY 2013;)

Sirtuin 1 Regulates Hepatitis B Virus Transcription and Replication by Targeting Transcription Factor AP-1

ABSTRACT Chronic hepatitis B virus (HBV) infection is a major risk factor for liver cirrhosis and hepatocellular carcinoma. Nevertheless, the molecular mechanism of HBV replication remains elusive. SIRT1 is a class III histone deacetylase that is a structure component of the HBV cccDNA minichromosome. In this study, we found by using microarray-based gene expression profiling analysis that SIRT1 was upregulated in HBV-expressing cells. Gene silencing of SIRT1 significantly inhibited HBV DNA replicative intermediates, 3.5-kb mRNA, and core protein levels. In contrast, the overexpression of SIRT1 augmented HBV replication. Furthermore, SIRT1 enhanced the activity of HBV core promoter by targeting transcription factor AP-1. The c-Jun subunit of AP-1 was bound to the HBV core promoter region, as demonstrated by using a chromatin immunoprecipitation assay. Mutation of AP-1 binding site or knockdown of AP-1 abolished the effect of SIRT1 on HBV replication. Finally, SIRT1 inhibitor sirtinol also suppressed the HBV DNA replicative intermediate, as well as 3.5-kb mRNA. Our study identified a novel host factor, SIRT1, which may facilitate HBV replication in hepatocytes. These data suggest a rationale for the use of SIRT1 inhibitor in the treatment of HBV infection.

SIRT6 Overexpression Potentiates Apoptosis Evasion in Hepatocellular Carcinoma via BCL2-Associated X Protein-Dependent Apoptotic Pathway.

Purpose: To characterize the functional role of SIRT6 in hepatocellular carcinoma (HCC). Experimental Design: The expression of SIRT6 in 60 paired paraffin-embedded HCC tissues and adjacent nontumoral liver tissues was examined by immunohistochemistry. The expression of SIRT6 in 101 paired frozen HCC tissues and adjacent nontumoral liver tissues was analyzed by Western blotting analysis and qPCR. The biologic consequences of overexpression and knockdown of SIRT6 in HCC cell lines were studied in vitro and in vivo. Results: SIRT6 expression was frequently upregulated in clinical HCC samples, and its expression was highly associated with tumor grade (P = 0.02), tumor size (P = 0.02), vascular invasion (P = 0.004), and shorter survival (P = 0.024). Depletion of SIRT6 from multiple liver cancer cell lines inhibited their growth and induced apoptosis in vitro. At the molecular level, we observed that the activation of the BCL2-associated X protein (Bax) signaling pathway, a major pathway that determines cancer cell apoptosis, is regulated by SIRT6 via its deacetylase activity. SIRT6 was recruited to the promoter of Bax, where it deacetylated histone 3 lysine 9 and suppressed its promoter activity. Binding of transcription factors (p53 and E2F-1) to Bax promoter was also generally increased in SIRT6-depleted cells. In mouse xenografts, SIRT6 suppression inhibited tumor growth and induced apoptosis. Finally, there is a negative correlation between SIRT6 and Bax mRNA expressions in human HCC samples. Conclusions: SIRT6 is an important protumorigenic factor in liver carcinogenesis. Thus, the therapeutic targeting of SIRT6 may offer options for HCC treatment. Clin Cancer Res; 22(13); 3372–82. ©2016 AACR.

Protective Role of Sirtuin3 (SIRT3) in Oxidative Stress Mediated by Hepatitis B Virus X Protein Expression

Background/Aim The hepatitis B virus (HBV) infection is accompanied by the induction of oxidative stress, especially mediated by HBV X protein (HBx). Oxidative stress has been implicated in a series of pathological states, such as DNA damage, cell survival and apoptosis. However, the host factor by which cells protect themselves under this oxidative stress is poorly understood. Methodology/Principal Findings In this study, we first confirmed that HBV infection significantly induced oxidative stress. Moreover, viral protein HBx plays a major role in the oxidative stress induced by HBV. Importantly, we found that mitochondrial protein SIRT3 overexpression could decrease reactive oxygen species (ROS) induced by HBx while SIRT3 knockdown increased HBx-induced ROS. Importantly, SIRT3 overexpression abolished oxidative damage of HBx-expressing cells as evidenced by γH2AX and AP sites measurements. In contrast, SIRT3 knockdown promoted HBx-induced oxidative damage. In addition, we also observed that oxidant H2O2 markedly promoted HBV replication while the antioxidant N-acetyl-L-cysteine (NAC) inhibited HBV replication. Significantly, SIRT3 overexpression inhibited HBV replication by reducing cellular ROS level. Conclusions/Significance Collectively, these data suggest HBx expression induces oxidative stress, which promotes cellular oxidative damage and viral replication during HBV pathogenesis. Mitochondrial protein SIRT3 protected HBx expressing-cells from oxidative damage and inhibited HBV replication possibly by decreased cellular ROS level. These studies shed new light on the physiological significance of SIRT3 on HBx-induced oxidative stress, which can contribute to the liver pathogenesis.

Sirtuin 3 enhanced drug sensitivity of human hepatoma cells through glutathione S-transferase pi 1/JNK signaling pathway

SIRT3, a class III histone deacetylase, has been implicated in various cancers as a novel therapeutic target. In hepatocellular carcinoma (HCC), we previously reported that SIRT3 induced cell apoptosis by regulating GSK-3β/Bax signaling pathway. Downregulation of SIRT3 in HCC cells facilitates tumor cell survival. In this study, we found that chemotherapeutic agents (doxorubicin, cisplatin and epirubicin) and sorafenib treatment downregulated SIRT3 mRNA and protein levels in three HCC cell lines. MTS assay found that SIRT3 overexpression sensitized liver cancer cells to chemotherapeutic agents and sorafenib in SMMC-7721, Huh-7 and PLC/PRF/5 cell lines. Moreover, SIRT3 overexpression promoted chemotherapeutic agents-induced or sorafenib-induced apoptosis as evidenced by flow cytometry, enhanced PARP cleavage and enhanced Caspase-9 cleavage in three HCC cells. In contrast, SIRT3 silencing increased drug resistance of HCC cells to chemotherapeutic agents. Mechanistic study found that SIRT3 downregulated the mRNA and protein levels of glutathione S-transferase pi 1 (GSTP1), which is a member of phase II detoxification enzymes families involved in metabolizing for chemotherapeutic agents. Moreover, SIRT3 decreased the amount of GSTP1 that was associated with JNK, which finally contributed the activation of JNK activity and activation of downstream target c-Jun and Bim. Importantly, GSTP1 overexpression or JNK inhibitor abolished SIRT3-induced apoptosis in HCC cells exposed to chemotherapeutic agents. Finally, there was a negative correlation between SIRT3 expression and GSTP1 expression in human HCC tissues. Together, our findings revealed SIRT3 could enhance the drug sensitivity of HCC cells to an array of chemotherapeutic agents. SIRT3 may serve as a potential target for improving the chemosensitivity of HCC patients.

Cyclin D2 plays a regulatory role in HBV replication.

Hepatitis B virus (HBV) infection is the leading cause of liver diseases. However, the molecular mechanisms of HBV infection and carcinogenesis have not been fully elucidated. In this study, we found that cyclin D2 was upregualted in HBV-expressing cells and liver tissues of HBV-transgenic mice. Gene silencing of cyclin D2 inhibited HBV DNA replicative intermediates, 3.5 kb mRNA, core protein level, as well as the secretions of HBsAg and HBeAg. On the contrary, overexpression of cyclin D2 promoted HBV replication. Furthermore, cyclin D2 regulated HBV replication by enhancing the activity of HBV core and Sp1 promoters by targeting transcription factor CREB2. Silencing of CREB2 abolished enhancement of HBV replication induced by cyclin D2. Together, our study has uncovered a positive role of cyclin D2 in HBV replication. It is conceivable that therapeutic application of cyclin D2 inhibitor in HBV infection therapy.

Interleukin-34 inhibits hepatitis B virus replication in vitro and in vivo

Background The hepatitis B virus (HBV) infection could activate the immune system and induce extensive inflammatory response. As the most important inflammatory factor, interleukins are critical for anti-viral immunity. Here we investigated whether interleukin-34 (IL-34) play a role in HBV infection. Methodology/Principal findings In this study, we first found that both serum IL-34 and IL-34 mRNA in PBMCs in chronic HBV patients was significantly decreased compared to the healthy controls. Furthermore, both IL-34 protein and mRNA levels were declined hepatoma cells expressing HBV. In addition, the clinical parameters analysis found that serum IL-34 was significantly associated with HBV DNA (P = 0.0066), ALT (P = 0.0327), AST (P = 0.0435), TB (P = 0.0406), DB (P = 0.0368) and AFP (P = 0.0225). Correlation analysis also found that serum IL-34 negatively correlated with HBV DNA copies, ALT and AST. In vitro studies found that IL-34 treatment in HepAD38 and HepG2.2.15 cells markedly inhibited HBV DNA, total RNA, 3.5kb mRNA and HBc protein. In vivo studies further demonstrated IL-34 treatment in HBV transgenic mice exhibited greater inhibition on HBV DNA, total RNA, 3.5kb mRNA and HBc protein, suggesting the effect to IL-34 on HBV is likely due to host innate or adaptive immune response. Conclusions/Significance Our study identified a novel interleukin, IL-34, which has anti-viral activity in HBV replication in hepatocytes in vitro and in vivo. These data suggest a rationale for the use of IL-34 in the HBV treatment.

ZEB2 inhibits HBV transcription and replication by targeting its core promoter

Hepatitis B virus (HBV) infection is a major cause of liver diseases, especially liver cirrhosis and hepatocellular carcinoma. However, the interaction between host and HBV has not been fully elucidated. ZEB2 is a Smad-interacting, multi-zinc finger protein that acts as a transcription factor or repressor for several signaling pathways. This study found that the expression of ZEB2 was decreased in HBV-expressing cells. Overexpression of ZEB2 inhibited HBV DNA replicative intermediates, 3.5kb mRNA, core protein level, and the secretion of HBsAg and HBeAg. In contrast, ZEB2 knockdown promoted HBV replication. Furthermore, ZEB2 could bind to HBV core promoter and inhibit its promoter activity. Mutation at the ZEB2 binding site in HBV core promoter eradicated ZEB2-mediated inhibition of HBV replication. This study identifies ZEB2 as a novel host restriction factor that inhibits HBV replication in hepatocytes. These data may shed light on development of new antiviral strategies.

Deacetylation of Ku70 by SIRT6 attenuates Bax-mediated apoptosis in hepatocellular carcinoma

SIRT6 is a class III histone deacetylase that has been implicated in HCC development. We previously reported that SIRT6 potentiated apoptosis evasion in hepatocellular carcinoma by inhibiting both Bax expression and mitochondrial translocalization. However, the mechanism underlying SIRT6-mediated inhibition of Bax mitochondrial localization remains elusive. In this study, we found that although SIRT6 had no effect on the expression level of Ku70, SIRT6 could interact with Ku70 and deacetylate it. The increased acetylation of Ku70 in SIRT6-depleted cells disrupt its interaction with Bax, which finally resulted in Bax mitochondrial translocalization. Furthermore, lysine K542 on Ku70 was the target for deacetylation by SIRT6. Ku70K542Q mutation abolished suppression of association between Ku70 and Bax and caused redistribution of Bax to the cytosol in SIRT6-depleted cells. Finally, Ku70K542Q mutation could reversed the inhibition of growth and apoptosis promotion mediated by SIRT6 silencing. Together, our findings revealed SIRT6 could block the mitochondrial translocation of Bax and decrease the apoptotic ratio of HCC cells by deacetylation of Ku70. SIRT6 may serve as a promising target for developing targeted therapies for HCC in the future.

Interleukin-35 stimulates hepatitis B virus transcription and replication by targeting transcription factor HNF4α

Hepatitis B virus (HBV) infection is a major health problem worldwide. Interleukin-35 (IL-35) is a definite immunosuppressive cytokine belonging to the IL-12 family. Nevertheless, the role of IL-35 in HBV replication remains elusive. In this study, we found that the level of HBV DNA replicative intermediates detected by qPCR and Southern blotting analysis was significantly increased by rhIL-35 in a dose-dependent manner. Moreover, HBV 3.5 kb mRNA levels were up-regulated by rhIL-35. The HBV core protein level as well as the HBsAg and HBeAg secretion levels were also increased by rhIL-35. Moreover, a mechanistic study demonstrated that IL-35 promoted HBV replication by enhancing the HBV core promoter activity. Importantly, hepatocyte nuclear factor 4α (HNF4α) was probably the target of IL-35. Mutation of the HNF4α-binding site on HBV core promoter or silencing HNF4α abolished the enhancement of HBV replication induced by IL-35. Finally, rhIL-35 was able to increase HBV replication in HBV transgenic mice. Taken together, our findings demonstrated that IL-35 has a novel role in HBV replication.