Interaction between STAT-3 and HNF-3 leads to the activation of liver-specific hepatitis B virus enhancer 1 function

Direct and biologically significant interactions of human herpesvirus 8 interferon regulatory factor 1 with STAT3 and Janus kinase TYK2

Human herpesvirus 8 (HHV-8) encodes four viral interferon regulatory factors (vIRFs) that target cellular IRFs and/or other innate-immune and stress signaling regulators and suppress the cellular response to viral infection and replication. For vIRF-1, cellular protein targets include IRFs, p53, p53-activating ATM kinase, BH3-only proteins, and antiviral signaling effectors MAVS and STING; vIRF-1 inhibits each, with demonstrated or likely promotion of HHV-8 de novo infection and productive replication. Here, we identify direct interactions of vIRF-1 with STAT3 and STAT-activating Janus kinase TYK2 (the latter reported previously by us to be inhibited by vIRF-1) and suppression by vIRF-1 of cytokine-induced STAT3 activation. Suppression of active, phosphorylated STAT3 (pSTAT3) by vIRF-1 was evident in transfected cells and vIRF-1 ablation in lytically-reactivated recombinant-HHV-8-infected cells led to increased levels of pSTAT3. Using a panel of vIRF-1 deletion variants, regions of vIRF-1 required for interactions with STAT3 and TYK2 were identified, which enabled correlation of STAT3 signaling inhibition by vIRF-1 with TYK2 binding, independently of STAT3 interaction. A viral mutant expressing vIRF-1 deletion-variant Δ198-222 refractory for TYK2 interaction and pSTAT3 suppression was severely compromised for productive replication. Conversely, expression of phosphatase-resistant, protractedly-active STAT3 led to impaired HHV-8 replication. Cells infected with HHV-8 mutants expressing STAT3-refractory vIRF-1 deletion variants or depleted of STAT3 displayed reduced vIRF-1 expression, while custom-peptide-promoted STAT3 interaction could effect increased vIRF-1 expression and enhanced virus replication. Taken together, our data identify vIRF-1 targeting and inhibition of TYK2 as a mechanism of STAT3-signaling suppression and critical for HHV-8 productive replication, the importance of specific pSTAT3 levels for replication, positive roles of STAT3 and vIRF-1-STAT3 interaction in vIRF-1 expression, and significant contributions to lytic replication of STAT3 targeting by vIRF-1.

Cabozantinib inhibits HBV-RNA transcription by decreasing STAT3 binding to the enhancer region of cccDNA

BACKGROUND

Precision medicine and customized therapeutics based on the features of each patient are important for maximizing therapeutic effects. Because most cases of HCC occur in the damaged liver through various etiologies, such as hepatitis virus infection, steatohepatitis, and autoimmune hepatitis, there should be a rationale for the choice of therapeutic options based on these etiologies. Although cabozantinib, an oral multikinase inhibitor, has demonstrated clinical effectiveness in advanced HCC, subgroup analyses showed a lower HR for death in HBV-related HCC. This study aimed to determine the therapeutic effects of cabozantinib in HBV-related HCC.

METHODS

Using HBV infection models and gene knockout cells, we determined the crucial signaling axis responsible for the effects of cabozantinib on HBV. A chromatin immunoprecipitation assay was performed to determine the interaction between the signaling molecules and HBV DNA. Agonists and inhibitors were used for confirmation.

RESULTS

Cabozantinib inhibited HBV replication through the HGF-mesenchymal-epithelial transition factor-signal transducer and activator of transcription 3 (MET-STAT3) signaling axis. The importance of STAT3 in viral replication has been confirmed using gene-edited STAT3 knockout cells. The chromatin immunoprecipitation assay revealed that the binding levels of phosphorylated STAT3 to enhancer region 1 of HBV covalently closed circular DNA were significantly increased by HGF stimulation.

CONCLUSIONS

Cabozantinib has favorable therapeutic effects on HBV-related HCC because it inhibits HCC not only directly but also indirectly by means of inhibitory effects on HBV.

Hypoxia-inducible factor affects hepatitis B virus transcripts and genome levels as well as the expression and subcellular location of the hepatitis B virus core protein

Globally, a chronic-hepatitis B virus (HBV) infection is the leading cause of hepatocellular carcinoma (HCC). The transcription factor hypoxia-inducible factor 1 (HIF1) is often elevated in HCC, including HBV-associated HCC. Previous studies have suggested that the expression of the HIF1 subunit, HIF1α, is elevated in HBV-infected hepatocytes; however, whether HIF1 activity affects the HBV lifecycle has not been fully explored. We used a liver-derived cell line and ex vivo cultured primary hepatocytes as models to determine how HIF1 affects the HBV lifecycle. We observed that HIF1 elevates HBV RNA transcript levels, core protein levels, core protein localization to the cytoplasm, and HBV genome replication. Attenuating the transcription activity of HIF1 blocked HIF1-mediated effects on the HBV lifecycle. Our studies show that HIF1 regulates various stages of the HBV lifecycle in hepatocytes and could be a therapeutic target for blocking HBV replication and the development of HBV-associated diseases.

Cellular Factors Involved in the Hepatitis D Virus Life Cycle

Hepatitis D virus (HDV) is a defective RNA virus with a negative-strand RNA genome encompassing less than 1700 nucleotides. The HDV genome encodes only for one protein, the hepatitis delta antigen (HDAg), which exists in two forms acting as nucleoproteins. HDV depends on the envelope proteins of the hepatitis B virus as a helper virus for packaging its ribonucleoprotein complex (RNP). HDV is considered the causative agent for the most severe form of viral hepatitis leading to liver fibrosis/cirrhosis and hepatocellular carcinoma. Many steps of the life cycle of HDV are still enigmatic. This review gives an overview of the complete life cycle of HDV and identifies gaps in knowledge. The focus is on the description of cellular factors being involved in the life cycle of HDV and the deregulation of cellular pathways by HDV with respect to their relevance for viral replication, morphogenesis and HDV-associated pathogenesis. Moreover, recent progress in antiviral strategies targeting cellular structures is summarized in this article.

STAT3 regulates antiviral immunity by suppressing excessive interferon signaling

This study identifies interleukin-6 (IL-6)-independent phosphorylation of STAT3 Y705 at the early stage of infection with several viruses, including influenza A virus (IAV). Such activation of STAT3 is dependent on the retinoic acid-induced gene I/mitochondrial antiviral-signaling protein/spleen tyrosine kinase (RIG-I/MAVS/Syk) axis and critical for antiviral immunity. We generate STAT3^Y705F/+ knockin mice that display a remarkably suppressed antiviral response to IAV infection, as evidenced by impaired expression of several antiviral genes, severe lung tissue injury, and poor survival compared with wild-type animals. Mechanistically, STAT3 Y705 phosphorylation restrains IAV pathogenesis by repressing excessive production of interferons (IFNs). Blocking phosphorylation significantly augments the expression of type I and III IFNs, potentiating the virulence of IAV in mice. Importantly, knockout of IFNAR1 or IFNLR1 in STAT3^Y705F/+ mice protects the animals from lung injury and reduces viral load. The results indicate that activation of STAT3 by Y705 phosphorylation is vital for establishment of effective antiviral immunity by suppressing excessive IFN signaling induced by viral infection.

Liver organoids: an in vitro 3D model for liver cancer study

Primary liver cancer (PLC) is the second leading cause of cancer mortality worldwide, and its morbidity unceasingly increases these years. Hepatitis B virus (HBV) infection accounted for approximately 50% of hepatocellular carcinoma (HCC) cases globally in 2015. Due to the lack of an effective model to study HBV-associated liver carcinogenesis, research has made slow progress. Organoid, an in vitro 3D model which maintains self-organization, has recently emerged as a powerful tool to investigate human diseases. In this review, we first summarize the categories and development of liver organoids. Then, we mainly focus on the functions of culture medium components and applications of organoids for HBV infection and HBV-associated liver cancer studies. Finally, we provide insights into a potential patient-derived organoid model from those infected with HBV based on our study, as well as the limitations and future applications of organoids in liver cancer research.

Mechanism of selenomethionine inhibiting of PDCoV replication in LLC-PK1 cells based on STAT3/miR-125b-5p-1/HK2 signaling

There are no licensed therapeutics or vaccines available against porcine delta coronavirus (PDCoV) to eliminate its potential for congenital disease. In the absence of effective treatments, it has led to significant economic losses in the swine industry worldwide. Similar to the current coronavirus disease 2019 (COVID-19) pandemic, PDCoV is trans-species transmissible and there is still a large desert for scientific exploration. We have reported that selenomethionine (SeMet) has potent antiviral activity against PDCoV. Here, we systematically investigated the endogenous immune mechanism of SeMet and found that STAT3/miR-125b-5p-1/HK2 signalling is essential for the exertion of SeMet anti-PDCoV replication function. Meanwhile, HK2, a key rate-limiting enzyme of the glycolytic pathway, was able to control PDCoV replication in LLC-PK1 cells, suggesting a strategy for viruses to evade innate immunity using glucose metabolism pathways. Overall, based on the ability of selenomethionine to control PDCoV infection and transmission, we provide a molecular basis for the development of new therapeutic approaches.

Signal transducer and activator of transcription 3 cooperates with androgen receptor/cell cycle-related kinase signalling pathway in the progression of hepatitis B virus infection and gender differences

The study aimed to investigate the role of androgen receptor (AR)/cell cycle-related kinase (CCRK) signalling pathway in chronic hepatitis B virus (HBV) infection and gender differences, and the contribution of AR regulatory factor signal transducer and activator of transcription 3 (STAT3) in it. AR, CCRK, and phosphorylated STAT3 expressions in liver tissues of chronic HBV-infected patients and non-HBV controls were determined by western blot and compared between genders. The relationships of expression levels with serum HBV DNA levels, liver inflammation activity, and fibrosis score were analysed in chronic HBV-infected patients. The relationships between expression levels of three proteins were also analysed. HBV-infected patients had significantly higher expression levels of AR, CCRK, and p-STAT3^Tyr705 compared with controls (p < .01). The expression levels of AR, CCRK, and p-STAT3^Tyr705 in chronic HBV-infected patients with severe inflammation were significantly higher than those with mild inflammation (p < .05). Expression levels in patients with heavier fibrosis (stage F4) were higher than in those with less fibrosis (stages F0-3) (p < .01). No gender differences were observed in AR, CCRK, and p-STAT3^Tyr705 levels in non-HBV controls; higher levels were observed in HBV-infected males than in HBV-infected females (p < .05). AR, CCRK, and p-STAT3^Tyr705 levels in liver tissues positively correlated with each other (p < .0001) and with serum HBV DNA levels (p < .0001). In conclusion, in this study, we first found concordant over-expression of AR, CCRK, and STAT3 in liver tissues of chronic HBV-infected patients who have not yet developed HCC, significantly correlated with the severity of the disease and showed gender differences. STAT3 may be a potential therapeutic co-target for chronic HBV infection.

Identification of STAU1 as a regulator of HBV replication by TurboID-based proximity labeling

The core promoter (CP) of hepatitis B virus (HBV) is critical for HBV replication by controlling the transcription of pregenomic RNA (pgRNA). Host factors regulating the activity of the CP can be identified by different methods. Biotin-based proximity labeling, a powerful method with the capability to capture weak or dynamic interactions, has not yet been used to map proteins interacting with the CP. Here, we established a strategy, based on the newly evolved promiscuous enzyme TurboID, for interrogating host factors regulating the activity of HBV CP. Using this strategy, we identified STAU1 as an important factor involved in the regulation of HBV CP. Mechanistically, STAU1 indirectly binds to CP mediated by TARDBP, and recruits the SAGA transcription coactivator complex to the CP to upregulate its activity. Moreover, STAU1 binds to HBx and enhances the level of HBx by stabilizing it in a ubiquitin-independent manner.

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HBV core promoter binding factors were interrogated by a proximity labeling method

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STAU1 enhances HBV transcription and replication

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STAU1 indirectly binds to core promoter via TARDBP and recruits SAGA complex

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STAU1 binds to HBx and increases its stability

Pathogenicity and virulence of Hepatitis B virus

Hepatitis B virus (HBV) is a hepatotropic virus and an important human pathogen. There are an estimated 296 million people in the world that are chronically infected by this virus, and many of them will develop severe liver diseases including hepatitis, cirrhosis and hepatocellular carcinoma (HCC). HBV is a small DNA virus that replicates via the reverse transcription pathway. In this review, we summarize the molecular pathways that govern the replication of HBV and its interactions with host cells. We also discuss viral and non-viral factors that are associated with HBV-induced carcinogenesis and pathogenesis, as well as the role of host immune responses in HBV persistence and liver pathogenesis.

STAT3: A key regulator in liver fibrosis

Janus protein tyrosine kinase (JAK) has the ability to activate signal transducer and activator of transcription (STAT). STAT3 is a valued member of the JAK/STAT signaling pathway. In recent years, several studies have documented that STAT3 is closely related to the occurrence and development of liver fibrosis caused by various factors. Activation of STAT3 can play anti- or pro-inflammatory roles in the pathogenesis of liver fibrosis. This article reviewed the recent studies on STAT3 in the development of various liver fibrosis to find a more effective method to relieve and cure liver diseases, such as hepatitis B virus (HBV), non-alcoholic fatty liver disease (NAFLD), schistosomiasis, and chemical liver injury.

Does Interleukin-6 Bridge SARS-CoV-2 With Virus-Associated Cancers?

To date SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), a member of the Coronaviridae family, has infected more than 40 million people worldwide. A second wave of SARS-CoV-2 infection is aggressively surging. The clinical worsening of SARS-CoV-2 infection appears to be strictly associated with comorbidities, which can be used to establish an intrinsic patient network whose molecular profile is pivotal for identifying and successfully treating populations at risk. Herein, we focus on the direct interaction between SARS-CoV-2 and virus-associated cancers, exploring the critical role of interleukin-6 (IL-6) as a mediator of this complex cross talk. IL-6 production is enhanced in diverse viral infections ranging from human papilloma virus (HPV) to hepatitis B virus (HBV), human immunodeficiency virus (HIV), and SARS-CoV-2 infection. High systemic levels of IL-6 are associated with viral persistence and poor clinical outcomes in SARS-CoV-2-infected patients. Blockade of IL-6/IL-6R, using specific molecules, is under investigation in active clinical trials for the treatment of patients with SARS-CoV-2. Although the data are as yet inconclusive, they pave the way for selective targeting of crucial cytokine-activated aberrant signaling in SARS-CoV-2 infection.

Signal transducer and activator of transcription 3 (STAT3) acts as a proviral factor for dengue virus propagation

Dengue fever is a significant mosquito-borne viral disease that affects millions of people every year. As a co-existing mechanism, DENV has evolved to evade elimination by the host antiviral immune system. DENV is reported to modulate host interferon response either by attenuating the factors that mediate interferon response like STAT1 and STAT2 or inhibiting the activation of STAT1 or by STAT2 degradation. Through this study we aim to understand how DENV modulates STAT3 mediated interferon response to its own advantage. We employed various techniques like Western blot, Confocal microscopy, RT-PCR to show that STAT3 acts as a pro-viral factor for DV-2 propagation. As per result of the present study STAT3 is upregulated as well as activated by phosphorylation in DV-2 infected A549 cells. Additionally, STAT3 knockdown led to a significant decrease in expression of viral proteins as well as viral replication. We show that DV-2 strategically tweaks STAT3 which is a negative regulator of Type I IFN signaling, in order to evade host Type I and Type III interferon response by upregulating its expression and activation. Our results demonstrate the proviral role of STAT3 for DV-2 propagation which is correlated to activation by tyrosine phosphorylation. Furthermore, since STAT3 is critical factor for DV-2 propagation, its modulation can facilitate targeted development of antivirals against Dengue.

The Functional and Antiviral Activity of Interferon Alpha-Inducible IFI6 Against Hepatitis B Virus Replication and Gene Expression

Hepatitis B virus is an enveloped DNA virus, that infects more than three hundred and sixty million people worldwide and leads to severe chronic liver diseases. Interferon-alpha inducible protein 6 (IFI6) is an IFN-stimulated gene (ISG) whose expression is highly regulated by the stimulation of type I IFN-alpha that restricts various kinds of virus infections by targeting different stages of the viral life cycle. This study aims to investigate the antiviral activity of IFI6 against HBV replication and gene expression. The IFI6 was highly induced by the stimulation of IFN-α in hepatoma cells. The overexpression of IFI6 inhibited while knockdown of IFI6 elevated replication and gene expression of HBV in HepG2 cells. Further study determined that IFI6 inhibited HBV replication by reducing EnhII/Cp of the HBV without affecting liver enriched transcription factors that have significant importance in regulating HBV enhancer activity. Furthermore, deletion mutation of EnhII/Cp and CHIP analysis revealed 100 bps (1715-1815 nt) putative sites involved in IFI6 mediated inhibition of HBV. Detailed analysis with EMSA demonstrated that 1715-1770 nt of EnhII/Cp was specifically involved in binding with IFI6 and restricted EnhII/Cp promoter activity. Moreover, IFI6 was localized mainly inside the nucleus to involve in the anti-HBV activity of IFI6. In vivo analysis based on the hydrodynamic injection of IFI6 expression plasmid along with HBV revealed significant inhibition of HBV DNA replication and gene expression. Overall, our results suggested a novel mechanism of IFI6 mediated HBV regulation that could develop potential therapeutics for efficient HBV infection treatment.

The Dynamic Interface of Viruses with STATs

Viruses commonly antagonize the antiviral type I interferon response by targeting signal transducer and activator of transcription 1 (STAT1) and STAT2, key mediators of interferon signaling. Other STAT family members mediate signaling by diverse cytokines important to infection, but their relationship with viruses is more complex. Importantly, virus-STAT interaction can be antagonistic or stimulatory depending on diverse viral and cellular factors. While STAT antagonism can suppress immune pathways, many viruses promote activation of specific STATs to support viral gene expression and/or produce cellular conditions conducive to infection. It is also becoming increasingly clear that viruses can hijack noncanonical STAT functions to benefit infection. For a number of viruses, STAT function is dynamically modulated through infection as requirements for replication change. Given the critical role of STATs in infection by diverse viruses, the virus-STAT interface is an attractive target for the development of antivirals and live-attenuated viral vaccines. Here, we review current understanding of the complex and dynamic virus-STAT interface and discuss how this relationship might be harnessed for medical applications.

EGF receptor inhibitors comprehensively suppress hepatitis B virus by downregulation of STAT3 phosphorylation

Current antiviral therapy can not cure chronic hepatitis B virus (HBV) infection or eliminate the risk of hepatocellular carcinoma. The licensed epidermal growth factor receptor (EGFR) inhibitors have found to inhibit hepatitis C virus replication via downregulation of signal transducers and activators of transcription 3 (STAT3) phosphorylation. Since STAT3 is also involved in HBV replication, we further studied the anti-HBV efficacy of the EGFR inhibitors in this study. HBV-transfected HepG2.2.15 cells and HBV-infected HepG2-NTCP cells were used as cell models, and HBV replication, the syntheses of viral antigens and the magnitude of the covalently closed circular DNA (cccDNA) reservoir were used as indictors to test the anti-HBV effects of EGFR inhibitors erlotinib and gefitinib. Erlotinib inhibited HBV replication with a half-maximal inhibitory concentration of 1.05 μM. It also reduced the syntheses of viral antigens at concentrations of 2.5 μM or higher. The underlying mechanism was possibly correlated with its inhibition on STAT3 phosphorylation via up-regulation of suppressor of cytokine signaling 3. Gefitinib also inhibited HBV replication and antigen syntheses. Compared with the commonest antiviral drug entecavir, these EGFR inhibitors additionally reduced hepatitis B e antigen and erlotinib also marginally affected the cccDNA reservoir in HBV-infected HepG2-NTCP cells. Interestingly, these promising anti-HBV effects were significantly enhanced by extension of treatment duration. In conclusion, EGFR inhibitors demonstrated a comprehensive anti-HBV potential, highlighting a new strategy to cure HBV infection and suggesting animal model-related studies or clinical try in the future.

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We test the anti-HBV potential of EGFR inhibitors erlotinib and gefitinib in vitro.

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Erlotinib inhibits HBV replication in clinically safe concentrations.

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EGFR inhibitors suppress HBV by downregulation of STAT3 phosphorylation.

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EGFR inhibitors show a comprehensive anti-HBV potential including the cccDNA.

Host Transcription Factors in Hepatitis B Virus RNA Synthesis

The hepatitis B virus (HBV) chronically infects over 250 million people worldwide and is one of the leading causes of liver cancer and hepatocellular carcinoma. HBV persistence is due in part to the highly stable HBV minichromosome or HBV covalently closed circular DNA (cccDNA) that resides in the nucleus. As HBV replication requires the help of host transcription factors to replicate, focusing on host protein–HBV genome interactions may reveal insights into new drug targets against cccDNA. The structural details on such complexes, however, remain poorly defined. In this review, the current literature regarding host transcription factors’ interactions with HBV cccDNA is discussed.

Association of STAT3 and STAT4 polymorphisms with susceptibility to chronic hepatitis B virus infection and risk of hepatocellular carcinoma: a meta-analysis

Background: It has been reported that polymorphisms of signal transducer and activator of transcription (STAT) 3 and STAT4 might be associated with susceptibility to hepatitis B virus (HBV) infection and risk of chronic hepatocellular carcinoma (HCC). Owing to limitation of sample size and inconclusive results, we conducted a meta-analysis to clarify the association. Methods: We identified relevant studies by a systematic search of Medline/PubMed, Embase, Web of Science and the Cochrane Library up to 20 February 2019. The strength of the association measured by odds ratios (OR) with 95% confidence intervals (CIs) was studied. All the statistical analyses were conducted based on Review Manager 5.3 software. Results: A total of 5242 cases and 2717 controls from five studies were included for the STAT3 polymorphism, 5902 cases and 7867 controls from nine studies for the STAT4 polymorphism. Our results suggested that STAT3 rs1053004 polymorphism was a significant risk factor of chronic HBV infection (C vs. T: OR = 1.17, 95% CI: 1.07–1.29, P_A=0.0007; CC + CT vs. TT: OR = 1.38, 95% CI: 1.09–1.76, P_A=0.008). Validation with all the genetic models revealed that rs7574865 polymorphism of STAT4 gene was closely associated with chronic HBV infection (P_A<0.01) and chronic hepatitis B (CHB)-related HCC (P_A<0.05). Meanwhile, the authenticity of the above meta-analysis results was confirmed by trial sequential analysis (TSA). Conclusions: The meta-analysis showed that STAT3 rs1053004 polymorphism may be the risk for developing chronic HBV infection but not associated with HCC. The present study also indicates that STAT4 rs7574865 polymorphism increased the risk of chronic HBV infection and HCC.

HoxA10 Facilitates SHP-1-Catalyzed Dephosphorylation of p38 MAPK/STAT3 To Repress Hepatitis B Virus Replication by a Feedback Regulatory Mechanism

Hepatitis B virus (HBV) infection is the leading cause of chronic hepatitis B (CHB), liver cirrhosis (LC), and hepatocellular carcinoma (HCC). This study reveals a distinct mechanism underlying the regulation of HBV replication. HBV activates homeobox A10 (HoxA10) in human hepatocytes, leukocytes, peripheral blood mononuclear cells (PBMCs), HepG2-NTCP cells, leukocytes isolated from CHB patients, and HBV-associated HCC tissues. HoxA10 in turn represses HBV replication in human hepatocytes, HepG2-NTCP cells, and BALB/c mice. Interestingly, we show that during early HBV infection, p38 mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3) were activated to facilitate HBV replication; however, during late HBV infection, HoxA10 was induced to attenuate HBV replication. Detailed studies reveal that HoxA10 binds to p38 MAPK, recruits SH2-containing protein tyrosine phosphatase 1 (SHP-1) to facilitate SHP-1 in catalyzing dephosphorylation of p38 MAPK/STAT3, and thereby attenuates p38 MAPK/STAT3 activation and HBV replication. Furthermore, HoxA10 binds to the HBV enhancer element I (EnhI)/X promoter, competes with STAT3 for binding of the promoter, and thereby represses HBV transcription. Taken together, these results show that HoxA10 attenuates HBV replication through repressing the p38 MAPK/STAT3 pathway by two approaches: HoxA10 interacts with p38 MAPK and recruits SHP-1 to repress HBV replication, and HoxA10 binds to the EnhI/X promoter and competes with STAT3 to attenuate HBV transcription. Thus, the function of HoxA10 is similar to the action of interferon (IFN) in terms of inhibition of HBV infection; however, the mechanism of HoxA10-mediated repression of HBV replication is different from the mechanism underlying IFN-induced inhibition of HBV infection.IMPORTANCE Two billion people have been infected with HBV worldwide; about 240 million infected patients developed chronic hepatitis B (CHB), and 650,000 die each year from liver cirrhosis (LC) or hepatocellular carcinoma (HCC). This work elucidates a mechanism underlying the control of HBV replication. HBV infection activates HoxA10, a regulator of cell differentiation and cancer progression, in human cells and patients with CHB and HCC. HoxA10 subsequently inhibits HBV replication in human tissue culture cells and mice. Additionally, HoxA10 interacts with p38 MAPK to repress the activation of p38 MAPK and STAT3 and recruits and facilitates SHP-1 to catalyze the dephosphorylation of p38 MAPK and STAT3. Moreover, HoxA10 competes with STAT3 for binding of the HBV X promoter to repress HBV transcription. Thus, this work reveals a negative regulatory mechanism underlying the control of HBV replication and provides new insights into the development of potential agents to control HBV infection.

Targeting STATs in neuroinflammation: The road less traveled!

JAK/STAT transduction pathway is a highly conserved pathway implicated in regulating cellular proliferation, differentiation, survival and apoptosis. Dysregulation of this pathway is involved in the onset of autoimmune, haematological, oncological, metabolic and neurological diseases. Over the last few years, the research of anti-neuroinflammatory agents has gained considerable attention. The ability to diminish the STAT-induced transcription of inflammatory genes is documented for both natural compounds (such as polyphenols) and chemical drugs. Among polyphenols, quercetin and curcumin directly inhibit STAT, while Berberis vulgaris L. and Sophora alopecuroides L extracts act indirectly. Also, the Food and Drug Administration has approved several JAK/STAT inhibitors (direct or indirect) for treating inflammatory diseases, indicating STAT can be considered as a therapeutic target for neuroinflammatory pathologies. Considering the encouraging data obtained so far, clinical trials are warranted to demonstrate the effectiveness and potential use in the clinical practice of STAT inhibitors to treat inflammation-associated neurodegenerative pathologies.

STAT3 roles in viral infection: antiviral or proviral?

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor which can be activated by cytokines, growth factor receptors, and nonreceptor-like tyrosine kinase. An activated STAT3 translocates into the nucleus and combines with DNA to regulate the expression of target genes involved in cell proliferation, differentiation, apoptosis and metastasis. Recent studies have shown that STAT3 plays important roles in viral infection and pathogenesis. STAT3 exhibits a proviral function in several viral infections, including those of HBV, HCV, HSV-1, varicella zoster virus, human CMV and measles virus. However, in some circumstances, STAT3 has an antiviral function in other viral infections, such as enterovirus 71, severe acute respiratory syndrome coronavirus and human metapneumovirus. This review summarizes the roles of STAT3 in viral infection and pathogenesis, and briefly discusses the molecular mechanisms involved in these processes.

CRISPR/Cas9-mediated knockout of HBsAg inhibits proliferation and tumorigenicity of HBV-positive hepatocellular carcinoma cells

Chronic hepatitis B virus (HBV) infection remains the most common risk factor for hepatocellular carcinoma (HCC). High HBV surface antigen (HBsAg) levels are highly correlated with hepatocarcinogenesis and HBV‐associated HCC development. However, the role and detailed mechanisms associated with HBsAg in HCC development remain elusive. In this study, we designed specific single guide RNAs (sgRNAs) targeting the open reading frames, preS1/preS2/S, of the HBV genome and established HBsAg knockout HCC cell lines using the CRISPR/Cas9 system. We showed that knockout of HBsAg in HCC cell lines decreased HBsAg expression and significantly attenuated HCC proliferation in vitro, as well as tumorigenicity in vivo. We also found that overexpression of HBsAg, including the large (LHBs), middle (MHBs), and small (SHBs) surface proteins promoted proliferation and tumor formation in HCC cells. Moreover, we demonstrated that knockout of HBsAg in HCC cells decreased interleukin (IL)‐6 production and inhibited signal transducer and activator of transcription 3 (STAT3) signaling, while overexpression of HBsAg induced a substantial accumulation of pY‐STAT3. Collectively, these results highlighted the tumorigenic role of HBsAg and implied that the IL‐6‐STAT3 pathway may be implicated in the HBsAg‐mediated malignant potential of HBV‐associated HCC.

Association of polymorphism rs1053005 in STAT3 with chronic hepatitis B virus infection in Han Chinese population

Background

Signal transducer and activator of transcription 3 (STAT3) is involved in hepatitis B virus (HBV) infection and HBV-related hepatocellular carcinoma (HCC). The association between polymorphism rs1053005 and haplotypes formed by rs1053004 and rs1053005 in the 3′UTR of STAT3 and chronic HBV infection has yet to be investigated.

Methods

This study included 567 patients with chronic HBV infection (239 chronic hepatitis, 141 liver cirrhosis and 187 HCC), 98 HBV infection resolvers, and 169 healthy controls. STAT3 rs1053004 and rs1053005 polymorphisms were genotyped by TaqMan SNP Genotyping Assays.

Results

The rs1053004 genotype CC [P value by Bonferroni correction (P_c) = 0.002] and allele C (P_c = 0.019) were more frequent in patients with chronic HBV infection than in healthy controls. The rs1053005 genotype GG was also more frequent in patients with chronic HBV infection than in healthy controls (P_c = 0.046). The rs1053004-rs1053005 haplotype T-G was less frequent in patients with chronic HBV infection than in healthy controls (P_c < 0.001). Haplotype C-A was more frequent in patients with liver cirrhosis than in patients with HCC (P_c = 0.042). The rs1053004 genotype TC, rs1053005 genotype AG and rs1053004-rs1053005 haplotype T-A were associated with higher HBV DNA levels.

Conclusions

STAT3 rs1053004 and rs1053005 polymorphisms and haplotypes formed by rs1053004 and rs1053005 are associated with chronic HBV infection and the haplotypes appear to be also associated with the development of liver disease. Studies in large sample sizes of patients and control populations are required to verify and extend these findings.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0569-x) contains supplementary material, which is available to authorized users.

Viral manipulation of STAT3: Evade, exploit, and injure

Signal transducer and activator of transcription 3 (STAT3) is a key regulator of numerous physiological functions, including the immune response. As pathogens elicit an acute phase response with concerted activation of STAT3, they are confronted with two evolutionary options: either curtail it or employ it. This has important consequences for the host, since abnormal STAT3 function is associated with cancer development and other diseases. This review provides a comprehensive outline of how human viruses cope with STAT3-mediated inflammation and how this affects the host. Finally, we discuss STAT3 as a potential target for antiviral therapy.

MERS-CoV infection in humans is associated with a pro-inflammatory Th1 and Th17 cytokine profile

The Middle East respiratory syndrome coronavirus (MERS-CoV) has been recognized as a highly pathogenic virus to humans that infects the respiratory tract and is associated with high morbidity and mortality. Studies in animal models suggest that MERS-CoV infection induces a strong inflammatory response, which may be related to the severity of disease. Data showing the cytokine profiles in humans during the acute phase of MERS-CoV infection are limited. In this study, we have analyzed the profile of cytokine responses in plasma samples from patients with confirmed MERS-CoV infections (n = 7) compared to healthy controls (n = 13). The cytokine profiles, including T helper (Th) 1, Th2 and Th17 responses, were analyzed using cytometric bead array (CBA). A prominent pro-inflammatory Th1 and Th17 response was clearly seen in patients with MERS-CoV infection, with markedly increased concentrations of IFN-γ, TNF-α, IL-15 and IL-17 compared to controls. IL-12 expression levels showed no difference between patients with MERS-CoV infection and the healthy controls despite the significantly increased levels of IFN-α2 and IFN-γ (P < .01). No changes were observed in the levels of IL-2, IL-4, IL-5, IL-13, and TGF-α (P > .05). Our results demonstrate a marked pro-inflammatory cytokine response during the acute phase of MERS-CoV infection in humans.

Targeting blockage of STAT3 inhibits hepatitis B virus-related hepatocellular carcinoma

Hepatitis B virus (HBV) infection is a significant cause of liver disease pathogenesis, which results in the development of hepatic dysfunction, cirrhosis and hepatocellular carcinoma (HCC). Our previous studies showed that oncogene STAT3 might be an ideal target for HCC therapy. Here, we investigated whether targeting blockage of STAT3 signaling is efficient for HBV-related HCC. Based on the refractory of HCC and the persistence of HBV, in this study, we designed shRNAs targeting STAT3. The results showed that blocking STAT3 signaling by shRNAs could promote HBV positive HCC cell apoptosis and induce cell cycle arrest, resulting in HCC cell growth inhibition in vitro. Importantly, STAT3-shRNAs efficiently suppressed HBV replication, which would reduce HBV-derived stimulation to STAT3 signaling and augment STAT3-shRNAs-mediated anti-HCC effect. Finally, STAT3-shRNAs-mediated anti-HBV positive HCC effect was confirmed in xenograft nude mice. This study suggested that targeting STAT3 therapies such as STAT3-shRNAs may be an efficacious strategy for HBV-related HCC.

Inhibitory effects of metachromin A on hepatitis B virus production via impairment of the viral promoter activity

The currently available antiviral agents for chronic infection with hepatitis B virus (HBV) are pegylated interferon-α and nucleoside/nucleotide analogues, although it has been difficult to completely eliminate covalently closed circular DNA (cccDNA) from patients. To identify an antiviral compound targeting HBV core promoter, 15 terpenes originating from marine organisms were screened using a cell line expressing firefly luciferase under the control of the HBV core promoter. Metachromin A, which is a merosesquiterpene isolated from the marine sponge Dactylospongia metachromia, inhibited the viral promoter activity at the highest level among the tested compounds, and suppressed HBV production with an EC₅₀ value of 0.8 μM regardless of interferon signaling and cytotoxicity. The analysis on the structure-activity relationship revealed that the hydroquinone moiety, and the double bonds at carbon numbers-5 and -9 in metachromin A are crucial for anti-HBV activity. Furthermore, metachromin A reduced the protein level but not the RNA level of hepatic nuclear factor 4α, which mainly upregulates the activities of enhancer I/X promoter and enhancer II/core promoter. These results suggest that metachromin A can inhibit HBV production via impairment of the viral promoter activity. Antiviral agents targeting the viral promoter may ameliorate HBV-related disorders regardless of remaining cccDNA.

Hepatitis B Virus Activates Signal Transducer and Activator of Transcription 3 Supporting Hepatocyte Survival and Virus Replication

BACKGROUND & AIMS

The human hepatitis B virus (HBV) is a major cause of chronic hepatitis and hepatocellular carcinoma, but molecular mechanisms driving liver disease and carcinogenesis are largely unknown. We therefore studied cellular pathways altered by HBV infection.

METHODS

We performed gene expression profiling of primary human hepatocytes infected with HBV and proved the results in HBV-replicating cell lines and human liver tissue using real-time polymerase chain reaction and Western blotting. Activation of signal transducer and activator of transcription (STAT3) was examined in HBV-replicating human hepatocytes, HBV-replicating mice, and liver tissue from HBV-infected individuals using Western blotting, STAT3-luciferase reporter assay, and immunohistochemistry. The consequences of STAT3 activation on HBV infection and cell survival were studied by chemical inhibition of STAT3 phosphorylation and small interfering RNA-mediated knockdown of STAT3.

RESULTS

Gene expression profiling of HBV-infected primary human hepatocytes detected no interferon response, while genes encoding for acute phase and antiapoptotic proteins were up-regulated. This gene regulation was confirmed in liver tissue samples of patients with chronic HBV infection and in HBV-related hepatocellular carcinoma. Pathway analysis revealed activation of STAT3 to be the major regulator. Interleukin-6-dependent and -independent activation of STAT3 was detected in HBV-replicating hepatocytes in cell culture and in vivo. Prevention of STAT3 activation by inhibition of Janus tyrosine kinases as well as small interfering RNA-mediated knockdown of STAT3-induced apoptosis and reduced HBV replication and gene expression.

CONCLUSIONS

HBV activates STAT3 signaling in hepatocytes to foster its own replication but also to prevent apoptosis of infected cells. This very likely supports HBV-related carcinogenesis.

High Hepsin expression predicts poor prognosis in Gastric Cancer

Hepsin, a membrane-associated serine protease, is frequently upregulated in epithelial cancers and involved in cancer progression. Our study aims to describe the expression pattern and evaluate the clinical implication of hepsin in gastric cancer patients. The mRNA expression of hepsin was analyzed in 50 gastric cancer and matched non-tumor tissues, which was downregulated in 78% (39/50) of gastric cancer. By searching and analyzing four independent datasets from Oncomine, we obtained the similar results. Furthermore, we evaluated the hepsin expression by IHC in tissue microarray (TMA) containing 220 Gastric Cancer specimens. More importantly, Kaplan-Meier survival and Cox regression analyses were taken to access the prognosis of gastric cancer and predicted that hepsin protein expression was one of the significant and independent prognostic factors for overall survival of Gastric Cancer.

MicroRNA miR-204 and miR-1236 inhibit hepatitis B virus replication via two different mechanisms

Hepatitis B virus (HBV) is a major human pathogen. In this study, we found that miR-204 and miR-1236 were down-regulated in HBV-producing cells, and each could suppress HBV replication. Using a bioinformatic approach and a reporter assay, we identified miR-1236, which can reduce HBV replication and protein production by directly targeting at HBV specific mRNA. In contrast, miR-204 was identified by a microarray approach, and had no effect on HBV RNA and protein production. Surprisingly, miR-204 could inhibit HBV pregenomic RNA encapsidation and capsid assembly. We further demonstrated that HBV suppressed miR-204 expression via activating a host transcription factor STAT3. We established a positive feed-forward loop between HBV, miR-204 and STAT3. Interestingly, miR-204 has been considered as a tumor suppressor in some literature. Since the risk for hepatocellular carcinoma (HCC) is significantly increased in chronic HBV patients, it is possible that chronic suppression of miR-204 by HBV contributes to HCC incidence. Both miR-204 and miR-1236 might be useful for developing new therapeutics against HBV.

Single Nucleotide Polymorphisms in STAT3 and STAT4 and Risk of Hepatocellular Carcinoma in Thai Patients with Chronic Hepatitis B

Hepatitis B virus (HBV) infection is the leading cause of hepatocellular carcinoma (HCC) development. Recent studies demonstrated that single nucleotide polymorphisms (SNPs) rs2293152 in signal transducer and activator of transcription 3 (STAT3) and rs7574865 in signal transducer and activator of transcription 4 (STAT4) are associated with chronic hepatitis B (CHB)-related HCC in the Chinese population. We hypothesized that these polymorphisms might be related to HCC susceptibility in Thai population as well. Study subjects were divided into 3 groups consisting of CHB-related HCC (n=192), CHB without HCC (n=200) and healthy controls (n=190). The studied SNPs were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results showed that the distribution of different genotypes for both polymorphisms were in Hardy-Weinberg equilibrium (P>0.05). Our data demonstrated positive association of rs7574865 with HCC risk when compared to healthy controls under an additive model (GG versus TT: odds ratio (OR) =2.07, 95% confidence interval (CI)=1.06-4.03, P=0.033). This correlation remained significant under allelic and recessive models (OR=1.46, 95% CI=1.09-1.96, P=0.012 and OR=1.71, 95% CI=1.13-2.59, P=0.011, respectively). However, no significant association between rs2293152 and HCC development was observed. These data suggest that SNP rs7574865 in STAT4 might contribute to progression to HCC in the Thai population.

Roles of hepatocyte nuclear factors in hepatitis B virus infection

Approximately 350 million people are estimated to be persistently infected with hepatitis B virus (HBV) worldwide. HBV maintains persistent infection by employing covalently closed circular DNA (cccDNA), a template for all HBV RNAs. Chronic hepatitis B (CHB) patients are currently treated with nucleos(t)ide analogs such as lamivudine, adefovir, entecavir, and tenofovir. However, these treatments rarely cure CHB because they are unable to inhibit cccDNA transcription and inhibit only a late stage in the HBV life cycle (the reverse transcription step in the nucleocapsid). Therefore, an understanding of the factors regulating cccDNA transcription is required to stop this process. Among numerous factors, hepatocyte nuclear factors (HNFs) play the most important roles in cccDNA transcription, especially in the generation of viral genomic RNA, a template for HBV replication. Therefore, proper control of HNF function could lead to the inhibition of HBV replication. In this review, we summarize and discuss the current understanding of the roles of HNFs in the HBV life cycle and the upstream factors that regulate HNFs. This knowledge will enable the identification of new therapeutic targets to cure CHB.

Hepatitis B Virus Middle Protein Enhances IL-6 Production via p38 MAPK/NF-κB Pathways in an ER Stress-Dependent Manner

During hepatitis B virus (HBV) infection, three viral envelope proteins of HBV are overexpressed in the endoplasmic reticulum (ER). The large S protein (LHBs) and truncated middle S protein (MHBs^t) have been documented to play roles in regulating host gene expression and contribute to hepatic disease development. As a predominant protein at the ultrastructural level in biopsy samples taken from viremic patients, the role of the middle S protein (MHBs) remains to be understood despite its high immunogenicity. When we transfected hepatocytes with an enhanced green fluorescent protein (EGFP)-tagged MHBs expressing plasmid, the results showed that expression of MHBs cause an upregulation of IL-6 at the message RNA and protein levels through activating the p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappa B (NF-κB) pathways. The use of specific inhibitors of the signaling pathways can diminish this upregulation. The use of BAPTA-AM attenuated the stimulation caused by MHBs. We further found that MHBs accumulated in the endoplasmic reticulum and increased the amount of glucose regulated protein 78 (GRP78/BiP). Our results provide a possibility that MHBs could be involved in liver disease progression.

Hepatitis B virus molecular biology and pathogenesis

As obligate intracellular parasites, viruses need a host cell to provide a milieu favorable to viral replication. Consequently, viruses often adopt mechanisms to subvert host cellular signaling processes. While beneficial for the viral replication cycle, virus-induced deregulation of host cellular signaling processes can be detrimental to host cell physiology and can lead to virus-associated pathogenesis, including, for oncogenic viruses, cell transformation and cancer progression. Included among these oncogenic viruses is the hepatitis B virus (HBV). Despite the availability of an HBV vaccine, 350-500 million people worldwide are chronically infected with HBV, and a significant number of these chronically infected individuals will develop hepatocellular carcinoma (HCC). Epidemiological studies indicate that chronic infection with HBV is the leading risk factor for the development of HCC. Globally, HCC is the second highest cause of cancer-associated deaths, underscoring the need for understanding mechanisms that regulate HBV replication and the development of HBV-associated HCC. HBV is the prototype member of the Hepadnaviridae family; members of this family of viruses have a narrow host range and predominately infect hepatocytes in their respective hosts. The extremely small and compact hepadnaviral genome, the unique arrangement of open reading frames, and a replication strategy utilizing reverse transcription of an RNA intermediate to generate the DNA genome are distinguishing features of the Hepadnaviridae. In this review, we provide a comprehensive description of HBV biology, summarize the model systems used for studying HBV infections, and highlight potential mechanisms that link a chronic HBV-infection to the development of HCC. For example, the HBV X protein (HBx), a key regulatory HBV protein that is important for HBV replication, is thought to play a cofactor role in the development of HBV-induced HCC, and we highlight the functions of HBx that may contribute to the development of HBV-associated HCC.

Association of Single Nucleotide Polymorphism rs1053004 in Signal Transducer and Activator of Transcription 3 (STAT3) with Susceptibility to Hepatocellular Carcinoma in Thai Patients with Chronic Hepatitis B

The single nucleotide polymorphism (SNP) rs1053004 in Signal transducer and activator of transcription 3 (STAT3) was recently reported to be associated with chronic hepatitis B (CHB)-related hepatocellular carcinoma (HCC) in a Chinese cohort. This study was aimed at investigating whether the SNP might also contribute to HCC susceptibility in the Thai population. Study subjects were enrolled and divided into 3 groups including CHB-related HCC (n=211), CHB without HCC (n=233) and healthy controls (n=206). The SNP was genotyped using allelic discrimination assays based on TaqMan real-time PCR. Data analysis revealed that the distribution of different genotypes was in Hardy-Weinberg equilibrium (P>0.05). The frequencies of allele T (major allele) in HCC patients, CHB patients and healthy controls were 51.4%, 58.6% and 61.4%, respectively, whereas the frequencies of C allele (minor allele) were 48.6%, 41.4% and 38.6%. The C allele frequency was higher in HCC when compared with CHB patients (odds ratio (OR)=1.34, 95% confidence interval (CI)=1.02-1.74, P=0.032). The genotype of SNP rs1053004 (CC versus TT+TC) was significantly associated with an increased risk when compared with CHB patients (OR=1.83, 95% CI=1.13-2.99, P=0.015). In addition, we observed a similar trend of association when comparing HCC patients with healthy controls (OR=1.77, 95% CI=1.07-2.93, P=0.025) and all controls (OR=1.81, 95% CI=1.19-2.74, P=0.005). These findings suggest that the SNP rs1053004 in STAT3 might contribute to HCC susceptibility and could be used as a genetic marker for HCC in the Thai population.

Differential association of STAT3 and HK-II expression in hepatitis B virus- and hepatitis C virus-related hepatocellular carcinoma

STAT3 and hexokinase II (HK-II) are involved in viral infection and carcinogenesis of various cancers including hepatocellular carcinoma (HCC). The roles of STAT3 and HK-II in hepatitis B virus (HBV)- and hepatitis C virus (HCV)-related HCC remain largely unclear. This study examined STAT3 and HK-II expression in HBV- and HCV-related HCC, HBV-related liver fibrosis, and normal control liver by using tissue microarray and immunohistochemical method. Results showed that STAT3 expression in HBV-related HCC, HCV-related HCC, and HBV-related liver fibrosis was significantly higher than in control liver (P < 0.001, P = 0.016, and P = 0.005, respectively) and had no significant differences between these three diseased liver tissues. The HK-II expression in HBV-related HCC was significantly higher than that in HCV-related HCC, HBV-related liver fibrosis, and control liver (P = 0.007, P = 0.029, and P = 0.008, respectively) but had no significant elevation in and no significant differences between HCV-related HCC, HBV-related liver fibrosis, and control liver. The HK-II expression was significantly correlated to STAT3 expression in HBV-related HCC (P = 0.022), but no correlation was observed in HCV-related HCC, HBV-related liver fibrosis, and control liver. In conclusion, STAT3 expression is upregulated in both HBV- and HCV-related HCC, while HK-II is predominantly upregulated and correlated to STAT3 in HBV-related HCC. These differential expression and association may suggest the distinct roles of STAT3 and HK-II in hepatocarcinogenesis of HBV and HCV infection. Studies are needed to confirm the relationship of STAT3 and HK-II and to examine the underlying mechanisms. J. Med. Virol. 88:1552-1559, 2016. © 2016 Wiley Periodicals, Inc.

IL-6 Plays a Crucial Role in HBV Infection

Interleukin-6 (IL-6), a cytokine mainly produced by activated monocytes, has broad pleiotropic actions that affect the functions of a variety of lymphoid cells. The roles of IL-6 in regulating immunity to infections are currently being defined. Remarkably, IL-6-mediated cellular and humoral immune responses play a crucial role in determining the outcome of viral infection. This article reviews the current knowledge on the critical role of IL-6 in hepatitis B virus (HBV) infection. As a competent intermediary, IL-6 derived from activated monocytes plays an important role in promoting lymphocytes responses that are essential for effective viral control. However, as a mediator of inflammation, IL-6 is also involved in the development of HBV-induced liver cirrhosis and exacerbating liver injury. Overall, the current data point to IL-6 as an immunoregulatory cytokine in HBV infection. Immunotherapeutic strategies aimed at optimizing the beneficial effects of IL-6 in HBV infection may prove to be an ordeal in the future, as they should foster the strengths of IL-6 while circumventing potential drawbacks.

IL6 Inhibits HBV Transcription by Targeting the Epigenetic Control of the Nuclear cccDNA Minichromosome

The HBV covalently closed circular DNA (cccDNA) is organized as a mini-chromosome in the nuclei of infected hepatocytes by histone and non-histone proteins. Transcription from the cccDNA of the RNA replicative intermediate termed pre-genome (pgRNA), is the critical step for genome amplification and ultimately determines the rate of HBV replication. Multiple evidences suggest that cccDNA epigenetic modifications, such as histone modifications and DNA methylation, participate in regulating the transcriptional activity of the HBV cccDNA. Inflammatory cytokines (TNFα, LTβ) and the pleiotropic cytokine interleukin-6 (IL6) inhibit hepatitis B virus (HBV) replication and transcription. Here we show, in HepG2 cells transfected with linear HBV monomers and HBV-infected NTCP-HepG2 cells, that IL6 treatment leads to a reduction of cccDNA-bound histone acetylation paralleled by a rapid decrease in 3.5kb/pgRNA and subgenomic HBV RNAs transcription without affecting cccDNA chromatinization or cccDNA levels. IL6 repressive effect on HBV replication is mediated by a loss of HNF1α and HNF4α binding to the cccDNA and a redistribution of STAT3 binding from the cccDNA to IL6 cellular target genes.

The Complex Role of STAT3 in Viral Infections

Signal transducer and activators of transcription-3 (STAT3) regulates diverse biological functions including cell growth, differentiation, and apoptosis. In addition, STAT3 plays a key role in regulating host immune and inflammatory responses and in the pathogenesis of many cancers. Several studies reported differential regulation of STAT3 in a range of viral infections. Interestingly, STAT3 appears to direct seemingly contradictory responses and both pro- and antiviral roles of STAT3 have been described. This review summarized the currently known functions of STAT3 in the regulation of viral replication and pathogenesis of viral infections. Some of the key unanswered questions and the gap in our current understanding of the role of STAT3 in viral pathogenesis are discussed.

Possible role of tocopherols in the modulation of host microRNA with potential antiviral activity in patients with hepatitis B virus-related persistent infection: a systematic review

Hepatitis B virus (HBV) infection represents a serious global health problem and persistent HBV infection is associated with an increased risk of cirrhosis, hepatocellular carcinoma and liver failure. Recently, the study of the role of microRNA (miRNA) in the pathogenesis of HBV has gained considerable interest as well as new treatments against this pathogen have been approved. A few studies have investigated the antiviral activity of vitamin E (VE) in chronic HBV carriers. Herein, we review the possible role of tocopherols in the modulation of host miRNA with potential anti-HBV activity. A systematic research of the scientific literature was performed by searching the MEDLINE, Cochrane Library and EMBASE databases. The keywords used were 'HBV therapy', 'HBV treatment', 'VE antiviral effects', 'tocopherol antiviral activity', 'miRNA antiviral activity' and 'VE microRNA'. Reports describing the role of miRNA in the regulation of HBV life cycle, in vitro and in vivo available studies reporting the effects of VE on miRNA expression profiles and epigenetic networks, and clinical trials reporting the use of VE in patients with HBV-related chronic hepatitis were identified and examined. Based on the clinical results obtained in VE-treated chronic HBV carriers, we provide a reliable hypothesis for the possible role of this vitamin in the modulation of host miRNA profiles perturbed by this viral pathogen and in the regulation of some cellular miRNA with a suggested potential anti-HBV activity. This approach may contribute to the improvement of our understanding of pathogenetic mechanisms involved in HBV infection and increase the possibility of its management and treatment.

Interaction of signal transducer and activator of transcription 3 polymorphisms with hepatitis B virus mutations in hepatocellular carcinoma

Hepatitis B virus (HBV) mutations and signal transducer and activator of transcription 3 (STAT3) activation are closely associated with hepatocellular carcinoma (HCC). However, single nucleotide polymorphisms (SNPs) of STAT3 have not been implicated in HCC susceptibility. This study was designed to evaluate the effect of STAT3 SNPs and their interactions with HBV mutations on HCC risk. A total of 2,011 HBV-infected subjects (including 1,021 HCC patients) and 1,012 healthy controls were involved in this study. SNPs rs4796793 (-1697, C>G), rs2293152 (intron 11, C>G), and rs1053004 (3' untranslated region, T>C) were genotyped using quantitative polymerase chain reaction. HBV mutations were determined via direct sequencing. It was found that rs2293152 (GG versus CC) was significantly associated with HCC risk compared with the subjects without HCC, adjusting for age and sex (adjusted odds ratio [AOR], 1.30; 95% confidence interval [CI], 1.04-1.62). The impact of rs2293152 was greater in women compared with men. Compared with HCC-free HBV-infected subjects, rs2293152 GG was solely associated with HCC in women (AOR, 2.04; 95% CI, 1.15-3.61). rs2293152 GG was significantly associated with high viral load (≥1 × 10(4) copies/mL) (AOR, 1.37; 95%, CI 1.01-1.88) and increased frequencies of T1674C/G (AOR, 1.61; 95% CI, 1.06-2.46) and A1762T/G1764A (AOR, 1.64; 95% CI, 1.14-2.35). In multivariate regression analyses, multiplicative interaction of rs1053004 with T1674C/G significantly increased HCC risk, whereas rs2293152 and A1726C interaction reduced it, adjusting for covariates including HBV mutations in the enhancer II/basal core promoter/precore region; the interaction of rs4796793 with preS2 start codon mutation significantly increased HCC risk, adjusting for covariates including HBV mutations in the preS region.

CONCLUSION

STAT3 SNPs appear to predispose the host with HBV mutations to hepatocarcinogenesis, and this effect may differ in men versus women. STAT3 SNPs may have applicability in future HCC surveillance algorithms. (Hepatology 2013;57:2369-2377).

Genetic polymorphisms of epidermal growth factor in relation to risk of hepatocellular carcinoma: two case-control studies

BACKGROUND

Earlier, we reported a highly statistically significant association between T-helper 1 (Th1) and Th2 cytokine genotypes and hepatocellular carcinoma (HCC) risk among natives of southern Guangxi, China, a hyperendemic region for HCC. Epidermal growth factor (EGF) plays a critical role in malignant transformation of hepatocytes and tumor progression. A polymorphism in the EGF gene (61A > G) results in elevation of EGF in liver tissues and blood. Epidemiological data are sparse on the possible association between EGF genetic polymorphism and HCC risk.

METHODS

The EGF 61A > G polymorphism, multiple Th1 and Th2 genotypes, and environmental risk factors for HCC were determined on 117 HCC cases and 225 healthy control subjects among non-Asians of Los Angeles County, California, a low-risk population for HCC, and 250 HCC cases and 245 controls of southern Guangxi, China.

RESULTS

Following adjustment for all known or suspected HCC risk factors, non-Asians in Los Angeles who possessed at least one copy of the high activity 61*G allele of the EGF gene showed a statistically non-significant, 78% increased risk of HCC compared with those possessing the EGF A/A genotype. This EGF-HCC risk association significantly strengthened among heavy users of alcohol [odds ratio (OR) = 3.44, 95% confidence interval (CI) = 0.93-12.76, P = 0.065)], and among individuals carrying the high-risk Th1/Th2 genotypes for HCC (OR = 3.34, 95% CI = 1.24-9.03, P = 0.017). No association between EGF genotype and HCC risk was observed among Chinese in southern Guangxi, China.

CONCLUSION

Genetic polymorphism in the EGF gene resulting in elevated level of EGF, may contribute to HCC risk among low-risk non-Asians in Los Angeles.

Large hepatitis delta antigen activates STAT-3 and NF-κB via oxidative stress

Hepatitis delta virus (HDV) coinfection or superinfection in hepatitis B virus (HBV)-infected patients results in a more aggressive liver disease, with more often fulminant forms and more rapid progression to cirrhosis and hepatocellular carcinoma. The mechanism(s) for this pejorative evolution remains unclear. To explore a specific HDV pathogenesis, we used a model of transient transfection of plasmids expressing the small (sHDAg or p24) or the large (LHDAg or p27) delta antigen in hepatocyte cell lines. We found that the production of reactive oxygen species was significantly higher in cells expressing p27. Consequently, p27 activated the signal transducer and activator of transcription-3 (STAT-3) and the nuclear factor kappa B (NF-κB) via the oxidative stress pathway. Moreover in the presence of antioxidants (PDTC, NAC) or calcium inhibitors (TMB-8, BAPTA-AM, Ruthenium Red), p27-induced activation of STAT-3 and NF-κB was dramatically reduced. Similarly, using a mutated form of p27, where the cysteine 211-isoprenylation residue was replaced by a serine, a significant reduction of STAT-3 and NF-κB activation was seen, suggesting the involvement of isoprenylation in this process. Additionally, we show that p27 is able to induce oxidative stress through activation of NADPH oxidase-4. These results provide insight into the mechanisms by which p27 can alter intracellular events relevant to HDV-related liver pathogenesis.

Estrogen receptor α represses transcription of HBV genes via interaction with hepatocyte nuclear factor 4α

BACKGROUND & AIMS

Women with hepatitis B virus (HBV) infection usually have lower viral loads than men, reducing their risk of liver cancer. There are 2 androgen-responsive elements in the HBV enhancer I that contribute to higher viral titers in men. We investigated whether and how estrogen signaling affects progression of HBV infection.

METHODS

Ovariectomy and estrogen supplementation were used to evaluate the effect of estrogen on HBV titers in transgenic mice with replicating HBV in hepatocytes. The effect of estrogen signaling on transcription of HBV genes, and the mechanisms of regulation, were studied in HepG2 cells.

RESULTS

HBV titers increased in female mice after ovariectomy and decreased in male mice supplemented with estrogen. Hepatic expression of estrogen receptor (ER)-α was increased by estrogen exposure. In HepG2 cells, up-regulation of ER-α reduced HBV transcription, which required a specific region within enhancer I. Direct DNA binding of ER-α and histone deacetylase activity were not required for ER-α-mediated repression of HBV genes. Overexpression of hepatocyte nuclear factor (HNF)-4α, which binds to this region, overcame the repressive effect of ER-α. ER-α did not repress transcription of an HBV replicon with a mutant HNF-4α binding site within enhancer I. Coimmunoprecipitation assays showed an interaction between ER-α and HNF-4α; this interaction prevented HNF-4α binding to enhancer I and activation of HBV transcription.

CONCLUSIONS

Estrogen can repress transcription of HBV genes by up-regulating ER-α, which interacts with and alters binding of HNF-4α to the HBV enhancer I. These findings might account for the lower viral load and reduced incidence of liver cancer in HBV-infected women than men.

Effects of interferon-α/β on HBV replication determined by viral load

Interferons α and β (IFN-α/β) are type I interferons produced by the host to control microbial infections. However, the use of IFN-α to treat hepatitis B virus (HBV) patients generated sustained response to only a minority of patients. By using HBV transgenic mice as a model and by using hydrodynamic injection to introduce HBV DNA into the mouse liver, we studied the effect of IFN-α/β on HBV in vivo. Interestingly, our results indicated that IFN-α/β could have opposite effects on HBV: they suppressed HBV replication when viral load was high and enhanced HBV replication when viral load was low. IFN-α/β apparently suppressed HBV replication via transcriptional and post-transcriptional regulations. In contrast, IFN-α/β enhanced viral replication by inducing the transcription factor HNF3γ and activating STAT3, which together stimulated HBV gene expression and replication. Further studies revealed an important role of IFN-α/β in stimulating viral growth and prolonging viremia when viral load is low. This use of an innate immune response to enhance its replication and persistence may represent a novel strategy that HBV uses to enhance its growth and spread in the early stage of viral infection when the viral level is low.

Hepatitis B virus X protein stimulates IL-6 expression in hepatocytes via a MyD88-dependent pathway

BACKGROUND & AIMS

Hepatitis B virus (HBV) X protein (HBx) has been implicated in HBV-associated carcinogenesis by activating signal transduction pathways and influencing gene transcription in liver cells. We aimed to investigate the underlying mechanisms for HBx-induced production of interleukin-6 (IL-6), one of the major inflammatory mediators that stimulate hepatocellular carcinoma development.

METHODS

HBx was overexpressed in hepatic and hepatoma cell lines and IL-6 expression levels were measured by quantitative RT-PCR and ELISA. The activation of IRAK-1, ERKs/p38, and NF-κB was determined by Western blotting using specific anti-phosphoprotein antibodies. The role of MyD88 in these processes was analyzed by MyD88 RNAi and expression of an inactive MyD88 mutant.

RESULTS

Expression of HBx in hepatic and hepatoma cells led to a dramatic enhancement of IL-6 synthesis and secretion. Dysfunction of MyD88 in these cells prevented the HBx-triggered IL-6 production. HBx expression also activated downstream signaling proteins of MyD88 including IRAK-1, ERKs/p38, and NF-κB. Inactivation of these signaling molecules blocked IL-6 synthesis as well. HBx-stimulated the expression of MyD88.

CONCLUSIONS

In hepatocytes and hepatoma cells, HBx stimulates the production of IL-6 in a MyD88-dependent manner, indicating that parenchymal liver cells are an additional source of high levels of IL-6 in the HBV-infected liver microenvironment. HBx could be involved in HBV-mediated liver carcinogenesis, through this mechanism of action.

Advances in understanding the role of STAT3 in the pathogenesis of hepatocellular carcinoma

Signal transducer and activator of transcription 3 (STAT3) is an important nuclear transcription factor that, once activated, can regulate the transcription of target genes. STAT3 is overexpressed in hepatocellular carcinoma (HCC). It has been demonstrated that STAT3 can be activated by HBV, HCV and diverse oncoproteins. The dysregulation of STAT/SOCS signaling also results in constitutive activation of STAT3. Aberrantly activated STAT3 can contribute to the malignant transformation of liver cells and result in the occurrence of HCC by inducing dysregulation of c-Myc, EGFR, TGF, survivin and VEGF. This paper summarizes the critical role of STAT3 in the pathogenesis of HCC and explores the possibility of using STAT3 as a target for HCC therapy.