The hepatitis B virus X protein modulates hepatocyte proliferation pathways to stimulate viral replication. J Virol. 2010;84:2675-2686. [PMID: 20053744 DOI: 10.1128/jvi.02196-09]

HBx protein as a therapeutic target for functional cure of hepatitis B virus infection

Hepatitis B virus (HBV) is a major cause of acute and chronic liver disease and represents a major public health problem worldwide. Current antiviral therapies with nucleos(t)ide analogues can effectively suppressing viremia but are not curative, and have little or no impact upon the HBV cccDNA minichromosome or the portions of integrated HBV DNA. Several alternative therapeutic strategies targeted at viral components and life cycle are under intense investigation. This article highlights the reasons for considering HBx as a therapeutic target as this may allow targeting of both virus and disease. Recent studies focused at HBx have led to the identification of several new pharmacological agents and development of some novel therapeutic approaches that now deserve to be taken to the next level for better management of hepatitis B. Besides, new therapies could be combined with other established therapies, to provide a functional cure from hepatitis B infection.

HBV-Induced Carcinogenesis: Mechanisms, Correlation With Viral Suppression, and Implications for Treatment

BACKGROUND

Chronic hepatitis B virus (HBV) infection is a common but underdiagnosed and undertreated health condition and is the leading cause of hepatocellular carcinoma (HCC) worldwide. HBV (rated a Grade 1 carcinogen by the International Agency for Research on Cancer) drives the transformation of hepatocytes in multiple ways by inducing viral DNA integrations, genetic dysregulation, chromosomal translocations, chronic inflammation, and oncogenic pathways facilitated by some HBV proteins. Importantly, these mechanisms are active throughout all phases of HBV infection. Nevertheless, most clinical guidelines for antiviral therapy recommend treatment based on a complex combination of HBV DNA levels, transaminasemia, liver histology, and demographic factors, rather than prompt treatment for all people with infection.

AIMS

To determine if current frameworks for antiviral treatment address the impacts of chronic HBV infection particularly preventing cancer development.

MATERIALS AND METHODS

We reviewed the recent data demonstrating pro-oncogenic factors acting throughout a chronic HBV infection can be inhibited by antiviral therapy.

RESULTS

We extensively reviewed Hepatitis B virology data and correlating clinical outcome data. From thi, we suggest that new findings support simplifying and expanding treatment initiation to reduce the incidence ofnew infections, progressive liver disease, and risk of hepatocellular carcinoma. We also consider lessons learned from other blood-borne pathogens, including the benefits of antiviral treatment in preventing transmission, reducing stigma, and reframing treatment as cancer prevention.

CONCLUSION

Incorporating these practice changes into treatment is likely to reduce the overall burden of chronic HBV infections and HCC. Through this, we may better achieve the World Health Organization's goal of eliminating viral hepatitis as a public health threat and minimise its impact on people's lives.

Repurposing of CDK Inhibitors as Host Targeting Antivirals: A Mini- Review

Most of the antiviral drugs in the market are designed to target viral proteins directly. They are generally considered safe for human use. However, they also suffer from several inherent limitations, in particular, narrow-spectrum antiviral profiles and liability to drug resistance. The other strategy for antiviral drug development is targeting host factors, which are highly involved at different stages in the viral life cycle. In contrast to direct-acting antiviral agents, host-targeting antiviral ones normally exhibit broad-spectrum antiviral properties along with a much higher genetic barrier to drug resistance. Cyclin-dependent kinases (CDKs) represent one such host factor. In this review, we summarized a number of CDK inhibitors (CDKIs) of varied chemical scaffolds with demonstrated antiviral activity. Challenges and issues associated with the repurposing of CDKIs as antiviral agents were also discussed.

UBR7 E3 Ligase Suppresses Interferon-β Mediated Immune Signaling by Targeting Sp110 in Hepatitis B Virus-Induced Hepatocellular Carcinoma

A newly discovered E3 ubiquitin ligase, UBR7, plays a crucial role in histone H2BK120 monoubiquitination. Here, we report a novel function of UBR7 in promoting hepatitis B virus (HBV) pathogenesis, which further leads to HBV-induced hepatocellular carcinoma (HCC). Transcriptomics analysis from HCC patients revealed the deregulation of UBR7 in cancer. Remarkably, targeting UBR7, particularly its catalytic function, led to a significant decrease in viral copy numbers. We also identified the speckled family protein Sp110 as an important substrate of UBR7. Notably, Sp110 has been previously shown to be a resident of promyelocytic leukemia nuclear bodies (PML-NBs), where it remains SUMOylated, and during HBV infection, it undergoes deSUMOylation and exits the PML body. We observed that UBR7 ubiquitinates Sp110 at critical residues within its SAND domain. Sp110 ubiquitination downregulates genes in the type I interferon response pathway. Comparative analysis of RNA-Seq from the UBR7/Sp110 knockdown data set confirmed that the IFN-β signaling pathway gets deregulated in HCC cells in the presence of HBV. Single-cell RNA-Seq analysis of patient samples further confirmed the inverse correlation between the expression of Sp110/UBR7 and the inflammation score. Notably, silencing of UBR7 induces IRF7 phosphorylation, thereby augmenting interferon (IFN)-β and the downstream interferon-stimulated genes (ISGs). Further, wild-type but not the ubiquitination-defective mutant of Sp110 could be recruited to the type I interferon response pathway genes. Our study establishes a new function of UBR7 in non-histone protein ubiquitination, promoting viral persistence, and has important implications for the development of therapeutic strategies targeting HBV-induced HCC.

Antioxidants and Calcium Modulators Preclude in Vitro Hepatitis B Virus-Induced Mitochondrial Damage

BACKGROUND/AIMS

Hepatitis B virus induces mitochondrial damage via the production of reactive oxygen species and concomitant with deregulation of calcium homeostasis. The current study evaluates the potential of antioxidant and calcium modulators for inhibition of hepatitis B virus-induced mitochondrial damage using in vitro cell culture models.

MATERIALS AND METHODS

Hepatitis B virus-induced mitochondrial fragmentation was observed by immunofluorescence confocal micros- copy in hepatitis B virus-infected cell lines (HepG2 and HepAD38). Differential protein expression of mitochondrial fragmentation mark- ers, dynamin-related protein 1 and phospho-dynamin-related protein 1, were evaluated both pre- and posttreatment with antioxidant N-acetyl-l-cysteine and calcium modulators like 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakisacetoxymethyl ester, ethylene-bis (oxyethylenenitrilo) tetraacetic acid glycol ether diamine tetraacetic acid-acetoxymethyl ester, and ruthenium amine complex by western blot analysis.

RESULTS

A slight reduction in mitochondrial fragmentation in both cell lines was observed post-antioxidant treatment with a partial prevention observed with calcium modulators. The expression of phospho-dynamin-related protein 1 was significantly upregulated (P = .0007, P = .003) in both hepatitis B virus-infected cell lines compared to uninfected cells. In line with these observations, the expres- sion of dynamin-related protein 1 and phospho-dynamin-related protein 1 was found to be significantly downregulated with N-acetyl- l-cysteine treatment in both cell lines (P = .003, P = .002), respectively. A nonsignificant trend was observed in the case of calcium modulators treatment.

CONCLUSIONS

Current study indicates that the mitochondrial fragmentation induced by hepatitis B virus infection can be reduced after antioxidant treatment pointing toward exploring better drug targets for the prevention of hepatitis B virus-induced mitochondrial frag- mentation and associated liver damage.

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.

The role of regulatory T cells and follicular T helper cells in HBV infection

Hepatitis B has become one of the major global health threats, especially in developing countries and regions. Hepatitis B virus infection greatly increases the risk for liver diseases such as cirrhosis and cancer. However, treatment for hepatitis B is limited when considering the huge base of infected people. The immune response against hepatitis B is mediated mainly by CD8+ T cells, which are key to fighting invading viruses, while regulatory T cells prevent overreaction of the immune response process. Additionally, follicular T helper cells play a key role in B-cell activation, proliferation, differentiation, and formation of germinal centers. The pathogenic process of hepatitis B virus is generally the result of a disorder or dysfunction of the immune system. Therefore, we present in this review the critical functions and related biological processes of regulatory T cells and follicular T helper cells during HBV infection.

Relevance of HBx for Hepatitis B Virus-Associated Pathogenesis

The hepatitis B virus (HBV) counts as a major global health problem, as it presents a significant causative factor for liver-related morbidity and mortality. The development of hepatocellular carcinomas (HCC) as a characteristic of a persistent, chronic infection could be caused, among others, by the pleiotropic function of the viral regulatory protein HBx. The latter is known to modulate an onset of cellular and viral signaling processes with emerging influence in liver pathogenesis. However, the flexible and multifunctional nature of HBx impedes the fundamental understanding of related mechanisms and the development of associated diseases, and has even led to partial controversial results in the past. Based on the cellular distribution of HBx-nuclear-, cytoplasmic- or mitochondria-associated-this review encompasses the current knowledge and previous investigations of HBx in context of cellular signaling pathways and HBV-associated pathogenesis. In addition, particular focus is set on the clinical relevance and potential novel therapeutic applications in the context of HBx.

Mechanism of cell cycle regulation and cell proliferation during human viral infection

Over the history of the coevolution of Host viral interaction, viruses have customized the host cellular machinery into their use for viral genome replication, causing effective infection and ultimately aiming for survival. They do so by inducing subversions to the host cellular pathways like cell cycle via dysregulation of important cell cycle checkpoints by viral encoded proteins, arresting the cell cycle machinery, blocking cytokinesis as well as targeting subnuclear bodies, thus ultimately disorienting the cell proliferation. Both DNA and RNA viruses have been active participants in such manipulation resulting in serious outcomes of cancer. They achieve this by employing different mechanisms-Protein-protein interaction, protein-phosphorylation, degradation, redistribution, viral homolog, and viral regulation of APC at different stages of cell cycle events. Several DNA viruses cause the quiescent staged cells to undergo cell cycle which increases nucleotide pools logistically significantly persuading viral replication whereas few other viruses arrest a particular stage of cell cycle. This allows the latter group to sustain the infection which allows them to escape host immune response and support viral multiplication. Mechanical study of signaling such viral mediated pathways could give insight into understanding the etiology of tumorigenesis and progression. Overall this chapter highlights the possible strategies employed by DNA/RNA viral families which impact the normal cell cycle but facilitate viral infected cell replication. Such information could contribute to comprehending viral infection-associated disorders to further depth.

HIV-1-Mediated Acceleration of Oncovirus-Related Non-AIDS-Defining Cancers

With the advent of combination antiretroviral therapy (cART), overall survival has been improved, and the incidence of acquired immunodeficiency syndrome (AIDS)-defining cancers has also been remarkably reduced. However, non-AIDS-defining cancers among human immunodeficiency virus-1 (HIV-1)-associated malignancies have increased significantly so that cancer is the leading cause of death in people living with HIV in certain highly developed countries, such as France. However, it is currently unknown how HIV-1 infection raises oncogenic virus-mediated cancer risks in the HIV-1 and oncogenic virus co-infected patients, and thus elucidation of the molecular mechanisms for how HIV-1 expedites the oncogenic viruses-triggered tumorigenesis in the co-infected hosts is imperative for developing therapeutics to cure or impede the carcinogenesis. Hence, this review is focused on HIV-1 and oncogenic virus co-infection-mediated molecular processes in the acceleration of non-AIDS-defining cancers.

Interaction between the Hepatitis B Virus and Cellular FLIP Variants in Viral Replication and the Innate Immune System

During viral evolution and adaptation, many viruses have utilized host cellular factors and machinery as their partners. HBx, as a multifunctional viral protein encoded by the hepatitis B virus (HBV), promotes HBV replication and greatly contributes to the development of HBV-associated hepatocellular carcinoma (HCC). HBx interacts with several host factors in order to regulate HBV replication and evolve carcinogenesis. The cellular FADD-like IL-1β-converting enzyme (FLICE)-like inhibitory protein (c-FLIP) is a major factor that functions in a variety of cellular pathways and specifically in apoptosis. It has been shown that the interaction between HBx and c-FLIP determines HBV fate. In this review, we provide a comprehensive and detailed overview of the interplay between c-FLIP and HBV in various environmental circumstances. We describe strategies adapted by HBV to establish its chronic infection. We also summarize the conventional roles of c-FLIP and highlight the functional outcome of the interaction between c-FLIP and HBV or other viruses in viral replication and the innate immune system.

Kinases as Potential Therapeutic Targets for Anti-coronaviral Therapy

The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.

C-terminal-truncated hepatitis B virus X protein promotes hepatocarcinogenesis by activating the MAPK pathway

PURPOSE

C-terminally truncated hepatitis B virus X (ctHBx) is frequently detected in hepatocellular carcinoma (HCC) patients with hepatitis B virus (HBV) integrated into their genomes, but the molecular mechanisms of ctHBx-related oncogenic signaling remain unclear. In this study, the effects of ctHBx on HepG2 cells were investigated by measuring ctHBx-induced changes in the cell cycle-related target proteins cell division cycle 25C (cdc25C) and p53 downstream of the mitogen-activated protein kinase (MAPK) pathway.

MATERIALS AND METHODS

ctHBx lentiviruses were constructed and transfected into HepG2 cells. Then, we investigated HepG2 cell line function by conducting the Cell Counting Kit-8 (CCK8) assay, clone formation assay, scratch wound testing, Transwell assays and flow cytometry to examine cell cycle and apoptosis. Western blotting (WB) was performed to detect proteins related to and downstream of the extracellular signal-regulated kinase(ERK)/c-Jun N-terminal kinase(JNK)/p38 MAPK pathway, including cdc25C and p53.

RESULTS

ctHBx significantly enhanced the proliferation, migration, invasion and colony-forming capability of HepG2 cells. In addition, ctHBx activated the ERK/JNK/p38 MAPK signaling pathway to regulate cell viability by affecting the expression of cyclin-related proteins, including cdc25C and p53.

CONCLUSION

The present study demonstrates that ctHBx promote the formation and development of HCC via regulating MAPK/cdc25C and p53 axis. ctHBx should be the driving factor of HBV-induced hepatocarcinogenesis.

Calcium signaling in hepatitis B virus infection and its potential as a therapeutic target

As a ubiquitous second messenger, calcium (Ca2+) can interact with numerous cellular proteins to regulate multiple physiological processes and participate in a variety of diseases, including hepatitis B virus (HBV) infection, which is a major cause of hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. In recent years, several studies have demonstrated that depends on the distinct Ca2+ channels on the plasma membrane, endoplasmic reticulum, as well as mitochondria, HBV can elevate cytosolic Ca2+ levels. Moreover, within HBV-infected cells, the activation of intracellular Ca2+ signaling contributes to viral replication via multiple molecular mechanisms. Besides, the available evidence indicates that targeting Ca2+ signaling by suitable pharmaceuticals is a potent approach for the treatment of HBV infection. In the present review, we summarized the molecular mechanisms related to the elevation of Ca2+ signaling induced by HBV to modulate viral propagation and the recent advances in Ca2+ signaling as a potential therapeutic target for HBV infection. Video Abstract.

Mitochondrial dysfunction and liver disease: role, relevance, and potential for therapeutic modulation

Mitochondria are key organelles involved in energy production as well as numerous metabolic processes. There is a growing interest in the role of mitochondrial dysfunction in the pathogenesis of common chronic diseases as well as in cancer development. This review will examine the role mitochondria play in the pathophysiology of common liver diseases, including alcohol-related liver disease, non-alcoholic fatty liver disease, chronic hepatitis B and hepatocellular carcinoma. Mitochondrial dysfunction is described widely in the literature in studies examining patient tissue and in disease models. Despite significant differences in pathophysiology between chronic liver diseases, common mitochondrial defects are described, including increased mitochondrial reactive oxygen species production and impaired oxidative phosphorylation. We review the current literature on mitochondrial-targeted therapies, which have the potential to open new therapeutic avenues in the management of patients with chronic liver disease.

Modeling reveals no direct role of the extent of HBV DNA integrations on the outcome of infection

Hepatitis B virus (HBV) with its high prevalence and death toll is one of the most important infectious diseases to study. Yet, there is very little progress in the development of within-host models for HBV, which has subsequently hindered our understanding of this virus. The uncertainty around the proliferation of infected hepatocytes has been studied but never in association with other important biological continuous events such as integrations and superinfections. This is despite the fact that these processes affect the diversity and composition of infected cell population in the liver and an improved understanding of the cellular composition will undoubtedly assist in strategizing against this viral infection. Here, we developed novel mathematical models that incorporate these key biological processes and analyzed them both analytically and numerically. Unaffected by the extent of integrated DNA (IDNA), the outcome of HBV infection was primarily dictated by the balance between processes generating and killing infected hepatocytes containing covalent closed circular DNA (cccDNA). The superinfection was found to be a key process in the spread of HBV infection as its exclusion could not reproduce experimentally observed composition of infected hepatocytes at peak of acute HBV infection, a stage where our model predicts that infected hepatocytes most likely carry both cccDNA and IDNA. Our analysis further suggested the existence of some form of selective advantage of infected hepatocytes containing only IDNA to explain the viral dynamics observed during antiviral treatment and the transition from peak to acute infection. Finally, the fine line between liver destruction and resolution of acute HBV infection was found to be highly influenced by the fate of cccDNA during cellular proliferation.

Transaminase Elevations during Treatment of Chronic Hepatitis B Infection: Safety Considerations and Role in Achieving Functional Cure

While current therapies for chronic HBV infection work well to control viremia and stop the progression of liver disease, the preferred outcome of therapy is the restoration of immune control of HBV infection, allowing therapy to be removed while maintaining effective suppression of infection and reversal of liver damage. This “functional cure” of chronic HBV infection is characterized by the absence of detectable viremia (HBV DNA) and antigenemia (HBsAg) and normal liver function and is the goal of new therapies in development. Functional cure requires removal of the ability of infected cells in the liver to produce the hepatitis B surface antigen. The increased observation of transaminase elevations with new therapies makes understanding the safety and therapeutic impact of these flares an increasingly important issue. This review examines the factors driving the appearance of transaminase elevations during therapy of chronic HBV infection and the interplay of these factors in assessing the safety and beneficial nature of these flares.

An in vitro Study on the Role of Hepatitis B Virus X Protein C-Terminal Truncation in Liver Disease Development

Hepatitis B virus X protein C-terminal 127 amino acid truncation is often found expressed in hepatocellular carcinoma (HCC) tissue samples. The present in vitro study tried to determine the role of this truncation mutant in the hepatitis B-related liver diseases such as fibrosis, cirrhosis, HCC, and metastasis. HBx gene and its 127 amino acid truncation mutant were cloned in mammalian expression vectors and transfected in human hepatoma cell line. Changes in cell growth/proliferation, cell cycle phase distribution, expression of cell cycle regulatory genes, mitochondrial depolarization, and intracellular reactive oxygen species (ROS) level were analyzed. Green fluorescent protein (GFP)-tagged version of HBx and the truncation mutant were also created and the effects of truncation on HBx intracellular expression pattern and localization were studied. Effect of time lapse on protein expression pattern was also analyzed. The truncation mutant of HBx is more efficient in inducing cell proliferation, and causes more ROS production and less mitochondrial depolarization as compared with wild type (wt) HBx. In addition, gene expression is altered in favor of carcinogenesis in the presence of the truncation mutant. Furthermore, mitochondrial perinuclear aggregation is achieved earlier in the presence of the truncation mutant. Therefore, HBx C-terminal 127 amino acid truncation might be playing important roles in the development of hepatitis B-related liver diseases by inducing cell proliferation, altering gene expression, altering mitochondrial potential, inducing mitochondrial clustering and oxidative stress, and changing HBx expression pattern.

The Role of IGF/IGF-1R Signaling in Hepatocellular Carcinomas: Stemness-Related Properties and Drug Resistance

Insulin-like Growth Factor (IGF)/IGF-1 Receptor (IGF-1R) signaling is known to regulate stem cell pluripotency and differentiation to trigger cell proliferation, organ development, and tissue regeneration during embryonic development. Unbalanced IGF/IGF-1R signaling can promote cancer cell proliferation and activate cancer reprogramming in tumor tissues, especially in the liver. Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death, with a high incidence and mortality rate in Asia. Most patients with advanced HCC develop tyrosine kinase inhibitor (TKI)-refractoriness after receiving TKI treatment. Dysregulation of IGF/IGF-1R signaling in HCC may activate expression of cancer stemness that leads to TKI refractoriness and tumor recurrence. In this review, we summarize the evidence for dysregulated IGF/IGF-1R signaling especially in hepatitis B virus (HBV)-associated HCC. The regulation of cancer stemness expression and drug resistance will be highlighted. Current clinical treatments and potential therapies targeting IGF/IGF-1R signaling for the treatment of HCC will be discussed.

Synergistic Effect of MC-LR and C-Terminal Truncated HBx on HepG2 Cells and Their Effects on PP2A Mediated Downstream Target of MAPK Signaling Pathway

C-terminally truncated hepatitis B virus (HBV) X (ctHBx) infection and exposure to microcystins-LR (MC-LR) can lead to human hepatitis and liver cancer, but the mechanism associated with their synergistically effects not been fully elucidated. The ctHBx (HBxΔ4 and HBxΔ32) lentivirus were constructed and transfected into the HepG2 cells. Then we investigated the function of MC-LR and ctHBx using the molecular biology approaches, including enzyme-linked immunosorbent assay, clone formation assay, scratch wound testing, transwell assays, carried out flow cytometry respectively to examine cell cycle and apoptosis in each group, and detected the related proteins of HBx, MEK/ERK/JNK/p38 in mitogen-activated protein kinase (MAPK) pathway and the downstream proteins such as cdc2, cdc25C, and p53 by western blotting. We found that the protein phosphorylase 2A (PP2A) enzyme activity in MC-LR and HBxΔ32/HBxΔ4 groups decreased more than in MC-LR and HBx group at the same time point and MC-LR concentration (P < 0.05). Meanwhile the proliferation, migration, invasion and colony formation capability of HepG2 cells were significantly enhanced in MC-LR and ctHBx groups (P < 0.05). In addition the proportion of S stage cells in the MC-LR-treated HBxΔ32/HBxΔ4 groups was significantly greater than that in the untreated groups (P < 0.05). Furthermore, the protein expression of MAPK signaling pathway including phospho-MEK1/2, ERKl/2, p38, and JNK were up-regulated by MC-LR and HBxΔ32, and the expression of cyclin-related proteins, including p53, cdc25C, and cdc2 were also activated (P < 0.05). Taken together, our findings revealed the essential significance of the MC-LR and ctHBx on the PP2A/MAPK/p53, cdc25C and cdc2 axis in the formation and development of HCC and identified MC-LR and ctHBx as potential causal cofactors of hepatocarcinogenesis.

An updated literature review: how HBV X protein regulates the propagation of the HBV

Chronic HBV infection constitutes a burden on human beings and is closely associated with hepatocellular carcinoma. The propagation of the HBV is determined by many factors, and the HBV X protein (HBx) could have a significant influence on this. HBx is a regulatory protein that can directly or indirectly interact with many cellular proteins to affect both the propagation of the HBV and the activity of the host cells. In this review, we summarized the possible mechanisms by which HBx regulates HBV replication at transcriptional and post-transcriptional levels in various experimental systems.

The Multiple Roles of Hepatitis B Virus X Protein (HBx) Dysregulated MicroRNA in Hepatitis B Virus-Associated Hepatocellular Carcinoma (HBV-HCC) and Immune Pathways

Currently, the treatment of hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) [HBV-HCC] relies on blunt tools that are unable to offer effective therapy for later stage pathogenesis. The potential of miRNA to treat HBV-HCC offer a more targeted approach to managing this lethal carcinoma; however, the complexity of miRNA as an ancillary regulator of the immune system remains poorly understood. This review examines the overlapping roles of HBx-dysregulated miRNA in HBV-HCC and immune pathways and seeks to demonstrate that specific miRNA response in immune cells is not independent of their expression in hepatocytes. This interplay between the two pathways may provide us with the possibility of using candidate miRNA to manipulate this interaction as a potential therapeutic option.

Hepatitis B virus X protein boosts hepatocellular carcinoma progression by downregulating microRNA-137

BACKGROUND

Hepatocellular carcinoma (HCC) is a frequent diagnosed malignancy. microRNAs (miRs) are involved in various cellular processes during cancer development. This study attempted to probe the miR-based mechanism in hepatitis B virus X protein (HBx) small interfering RNA (siRNA)-treated HCC cells.

METHODS

HBx expression in hepatocyte and HCC cells was detected, and cells with highest HBx expression were screened out and transfected with HBx-siRNAs. Then the effect of HBx on HCC cell proliferation was detected. miRs differentially expressed in HBx-siRNA-transfected MHCC97H cells were analyzed and verified. miR-137 methylation was analyzed by bioinformatics, and miR-137 restoration was detected after Aza treatment. Furthermore, miR-137 methylation in MHCC97H cells with HBx knockdown or HBx overexpression was detected by methylation specific PCR. The targeting relationship between miR-137 and Notch1 was verified. Then the gain-and-loss functions of miR-137 or/and Notch1 were performed to estimate their roles in HCC cell proliferation. The effects of HBx-siRNA and overexpressed miR-137 in vivo were observed by tumor xenograft in nude mice and immunohistochemistry.

RESULTS

HBx-siRNA weakened MHCC97H cell proliferation and tumor growth. miR-137 was highly expressed in HBx-siRNA-treated HCC cells and targeted Notch1. HBx knockdown decreased miR-137 methylation and restored miR-137 expression. miR-137 overexpression prevented HCC cell proliferation and tumor growth, while miR-137 downregulation reversed the repressing effects of HBx-siRNA on HCC cell proliferation. Inhibition of Notch1 reversed HCC cell proliferation induced by miR-137 downregulation.

CONCLUSION

Overexpression of miR-137 blocks HCC cell proliferation in HBx-siRNA-treated MHCC97H cells by targeting Notch1. This study may offer novel target for HCC treatment.

SAMHD1 Functions and Human Diseases

Deoxynucleoside triphosphate (dNTP) molecules are essential for the replication and maintenance of genomic information in both cells and a variety of viral pathogens. While the process of dNTP biosynthesis by cellular enzymes, such as ribonucleotide reductase (RNR) and thymidine kinase (TK), has been extensively investigated, a negative regulatory mechanism of dNTP pools was recently found to involve sterile alpha motif (SAM) domain and histidine-aspartate (HD) domain-containing protein 1, SAMHD1. When active, dNTP triphosphohydrolase activity of SAMHD1 degrades dNTPs into their 2'-deoxynucleoside (dN) and triphosphate subparts, steadily depleting intercellular dNTP pools. The differential expression levels and activation states of SAMHD1 in various cell types contributes to unique dNTP pools that either aid (i.e., dividing T cells) or restrict (i.e., nondividing macrophages) viral replication that consumes cellular dNTPs. Genetic mutations in SAMHD1 induce a rare inflammatory encephalopathy called Aicardi-Goutières syndrome (AGS), which phenotypically resembles viral infection. Recent publications have identified diverse roles for SAMHD1 in double-stranded break repair, genome stability, and the replication stress response through interferon signaling. Finally, a series of SAMHD1 mutations were also reported in various cancer cell types while why SAMHD1 is mutated in these cancer cells remains to investigated. Here, we reviewed a series of studies that have begun illuminating the highly diverse roles of SAMHD1 in virology, immunology, and cancer biology.

Anti-Hepatitis B Virus Activity of Esculetin from Microsorium fortunei In Vitro and In Vivo

Coumarins are widely present in a variety of plants and have a variety of pharmacological activities. In this study, we isolated a coumarin compound from Microsorium fortunei (Moore) Ching; the compound was identified as esculetin by hydrogen and carbon spectroscopy. Its anti-hepatitis B virus (HBV) activity was investigated in vitro and in vivo. In the human hepatocellular liver carcinoma 2.2.15 cell line (HepG2.2.15) transfected with HBV, esculetin effecting inhibited the expression of the HBV antigens and HBV DNA in vitro. Esculetin inhibited the expression of Hepatitis B virus X (HBx) protein in a dose-dependent manner. In the ducklings infected with duck hepatitis B virus (DHBV), the levels of DHBV DNA, duck hepatitis B surface antigen (DHBsAg), duck hepatitis B e-antigen (DHBeAg), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) decreased significantly after esculetin treatment. Summing up the above, the results suggest that esculetin efficiently inhibits HBV replication both in vitro and in vivo, which provides an opportunity for further development of esculetin as antiviral drug.

Survivin expression starts before hepatocellular cancer development in the liver of chronic hepatitis B patients: a pilot, cross-sectional study

Introduction

Survivin expression is well known feature of hepatocellular carcinoma (HCC); however, there is no information about survivin expression in chronic hepatitis B (CHB).

Aim

Investigating survivin expression in the liver of CHB patients.

Material and methods

This is a single-centre, cross-sectional study. Seventy-five CHB patients and eight control patients were enrolled into the study between 2008 and 2018. Immunohistochemical study was performed by using anti-survivin antibody to evaluate survivin immunoreactivity.

Results

Survivin immunoreactivity was significantly higher in CHB patients compared to controls (p = 0.008). Also, the degree of survivin immunoreactivity was significantly higher in CHB patients (p = 0.027). Between the anti-survivin-positive and anti-survivin-negative groups, baseline laboratory parameters and initial pathology features were not significantly different.

Conclusions

This is the first study evaluating survivin expression in CHB patients. Understanding the possible relationship between survivin expression and HCC development in this population can promote new studies in terms of new therapies and treatment timing.

It takes a team: a gain-of-function story of p53-R249S

Gain-of-function (GOF), the most malicious oncogenic activity of a cancer-promoting protein, is well illustrated to three hotspot p53 mutations at R248, R175, and R273 with distinct molecular mechanisms. Yet, less is known about another hotspot p53 mutant, R249S (p53-R249S). p53-R249S is the sole hotspot mutation in hepatocellular carcinoma (HCC) that is highly associated with chronic hepatitis B virus (HBV) infection and dietary exposure to aflatoxin B1 (AFB1). Its GOF is suggested by the facts that this mutant is associated with earlier onset of HCC and poorer prognosis of cancer patients and that its overexpression drives HCC proliferation and tumorigenesis. By contrast, simply knocking in this mutant in normal mice did not show apparent GOF activity. Hence, the GOF activity for p53-R249S and its underlying mechanisms have been elusive until recent findings offered some new insights. This review will discuss these findings as well as their clinical significance and implications for the development of a strategy to target multiple molecules as a therapy for p53-R249S-harboring HCC.

Intertwined: SAMHD1 cellular functions, restriction, and viral evasion strategies

SAMHD1 was initially described for its ability to efficiently restrict HIV-1 replication in myeloid cells and resting CD4⁺ T cells. However, a growing body of evidence suggests that SAMHD1-mediated restriction is by far not limited to lentiviruses, but seems to be a general concept that applies to most retroviruses and at least a number of DNA viruses. SAMHD1 anti-viral activity was long believed to be solely due to its ability to deplete cellular dNTPs by enzymatic degradation. However, since its discovery, several new functions have been attributed to SAMHD1. It has been demonstrated to bind nucleic acids, to modulate innate immunity, as well as to participate in the DNA damage response and resolution of stalled replication forks. Consequently, it is likely that SAMHD1-mediated anti-viral activity is not or not exclusively mediated through its dNTPase activity. Therefore, in this review, we summarize current knowledge on SAMHD1 cellular functions and systematically discuss how these functions could contribute to the restriction of a broad range of viruses besides retroviruses: herpesviruses, poxviruses and hepatitis B virus. Furthermore, we aim to highlight different ways how viruses counteract SAMHD1-mediated restriction to bypass the SAMHD1-mediated block to viral infection.

Hepatitis B virus X reduces hepatocyte apoptosis and promotes cell cycle progression through the Akt/mTOR pathway in vivo

Hepatitis B virus X (HBx), a viral onco-protein encoded by HBV, can promote oncogenesis of HCC. However, the mechanism of HBx in hepatocarcinogenesis is still unclear. In this study, we establish a new mouse model with normal immune system to investigate the role of HBx and its functional mechanisms under normal immune function. The animal model was established by injecting HBx-EGFP-14-19 cells into the hepatic portal vein of KM mice. To verify the mouse model, the expression of HBx in the liver tissue of mice was detected by qRT-PCR, western blotting and immunohistochemistry. The apoptosis index was calculated using the terminal deoxynucleotidyl transferase-dUTP nick-end labeling (TUNEL) assay, and the expression levels of apoptosis-related and cell cycle-related factors were measured. Moreover, expression of proteins in the protein kinase B/mammalian target of rapamycin (Akt/mTOR) signaling pathway was detected in HBx-EGFP-14-19 mice with and without use of an Akt inhibitor. The results showed the HBx was successfully overexpressed in liver of KM mice. After overexpressing HBx, the apoptosis index was downregulated in HBx-EGFP-14-19 liver tissue, and the expression levels of caspase-9 and Bad were reduced, but Bcl-xl was increased in HBx-EGFP-14-19 liver tissue. Overexpression of HBx increased the expression of the cyclin-dependent kinase 2 (CDK2), cyclinD1 and cyclinE. Moreover, compared with the low-level HBx group, p-Akt and p-mTOR were increased in the livers of mice with high levels of HBx. However, inactivation of apoptosis by overexpression of HBx was abolished by the treatment with an Akt inhibitor. These results indicate that HBx can induce anti-apoptosis mechanisms in hepatocytes in vivo, which is mediated by the Akt/mTOR signaling pathway.

Phosphatase Cdc25A Negatively Regulates the Antiviral Immune Response by Inhibiting TBK1 Activity

The phosphatase Cdc25A plays an important role in cell cycle regulation by dephosphorylating its substrates, such as cyclin-dependent kinases. In this study, we demonstrate that Cdc25A negatively regulates RIG-I-mediated antiviral signaling. We found that ectopic expression of Cdc25A in 293T cells inhibits the activation of beta interferon (IFN-β) induced by Sendai virus and poly(I·C), while knockdown of Cdc25A enhances the transcription of IFN-β stimulated by RNA virus infection. The inhibitory effect of Cdc25A on the antiviral immune response is mainly dependent on its phosphatase activity. Data from a luciferase assay indicated that Cdc25A can inhibit TBK1-mediated activation of IFN-β. Further analysis indicated that Cdc25A can interact with TBK1 and reduce the phosphorylation of TBK1 at S172, which in turn decreases the phosphorylation of its downstream substrate IRF3. Consistently, knockdown of Cdc25A upregulates the phosphorylation of both TBK1-S172 and IRF3 in Sendai virus-infected or TBK1-transfected 293T cells. In addition, we confirmed that Cdc25A can directly dephosphorylate TBK1-S172-p. These results demonstrate that Cdc25A inhibits the antiviral immune response by reducing the active form of TBK1. Using herpes simplex virus 1 (HSV-1) infection, an IFN-β reporter assay, and reverse transcription-quantitative PCR (RT-qPCR), we demonstrated that Cdc25A can also inhibit DNA virus-induced activation of IFN-β. Using a vesicular stomatitis virus (VSV) infection assay, we confirmed that Cdc25A can repress the RIG-I-like receptor (RLR)-mediated antiviral immune response and influence the antiviral status of cells. In conclusion, we demonstrate that Cdc25A negatively regulates the antiviral immune response by inhibiting TBK1 activity.IMPORTANCE The RLR-mediated antiviral immune response is critical for host defense against RNA virus infection. However, the detailed mechanism for balancing the RLR signaling pathway in host cells is not well understood. We found that the phosphatase Cdc25A negatively regulates the RNA virus-induced innate immune response. Our studies indicate that Cdc25A inhibits the RLR signaling pathway via its phosphatase activity. We demonstrated that Cdc25A reduces TBK1 activity and consequently restrains the activation of IFN-β transcription as well as the antiviral status of nearby cells. We showed that Cdc25A can also inhibit DNA virus-induced activation of IFN-β. Taken together, our findings uncover a novel function and mechanism for Cdc25A in regulating antiviral immune signaling. These findings reveal Cdc25A as an important negative regulator of antiviral immunity and demonstrate its role in maintaining host cell homeostasis following viral infection.

A Survey of Molecular Heterogeneity in Hepatocellular Carcinoma

Understanding the heterogeneity of dysregulated pathways associated with the development of hepatocellular carcinoma (HCC) may provide prognostic and therapeutic avenues for disease management. As HCC involves a complex process of genetic and epigenetic modifications, we evaluated expression of both polyadenylated transcripts and microRNAs from HCC and liver samples derived from two cohorts of patients undergoing either partial hepatic resection or liver transplantation. Copy number variants were inferred from whole genome low‐pass sequencing data, and a set of 56 cancer‐related genes were screened using an oncology panel assay. HCC was associated with marked transcriptional deregulation of hundreds of protein‐coding genes. In the partially resected livers, diminished transcriptional activity was observed in genes associated with drug catabolism and increased expression in genes related to inflammatory responses and cell proliferation. Moreover, several long noncoding RNAs and microRNAs not previously linked with HCC were found to be deregulated. In liver transplant recipients, down‐regulation of genes involved in energy production and up‐regulation of genes associated with glycolysis were detected. Numerous copy number variants events were observed, with hotspots on chromosomes 1 and 17. Amplifications were more common than deletions and spanned regions containing genes potentially involved in tumorigenesis. Colony stimulating factor 1 receptor (CSF1R), fibroblast growth factor receptor 3 (FGFR3), fms‐like tyrosine kinase 3 (FLT3), nucleolar phosphoprotein B23 (NPM1), platelet‐derived growth factor receptor alpha polypeptide (PDGFRA), phosphatase and tensin homolog (PTEN), G‐protein‐coupled receptors‐like receptor Smoothened (SMO), and tumor protein P53 (TP53) were mutated in all tumors; another 26 cancer‐related genes were mutated with variable penetrance. Conclusion: Our results underscore the marked molecular heterogeneity between HCC tumors and reinforce the notion that precision medicine approaches are needed for management of individual HCC. These data will serve as a resource to generate hypotheses for further research to improve our understanding of HCC biology. (Hepatology Communications 2018; 00:000‐000)

Cyclin E2-CDK2 mediates SAMHD1 phosphorylation to abrogate its restriction of HBV replication in hepatoma cells

SAMHD1 inhibits Hepatitis B virus (HBV) replication by reducing the intracellular dNTP levels. However, how SAMHD1 phosphorylation is regulated to abrogate its restriction of HBV replication in hepatoma cells is poorly understood. Here, we show that HBV replication and SAMHD1 phosphorylation levels are significantly reduced by knocking down cyclin-dependent kinase (CDK) 2 expression or in the presence of a CDK2 inhibitor. SAMHD1 binds to CDK2 in hepatocarcinoma cells, and this interaction does not require the HBV core protein. Furthermore, cyclin E2 participates in regulating viral replication through the CDK2/SAMHD1 phosphorylation pathway in an HBV infection system. Collectively, our results provide evidence that CDK2 has a greater role in regulating SAMHD1 phosphorylation and HBV replication than CDK1 or CDK6.

Hepatitis B Virus X Protein Upregulates Intracellular Calcium Signaling by Binding C-terminal of Orail Protein

Hepatitis B virus X (HBx) protein plays a pivotal role in the development of hepatitis B virus (HBV)-associated hepatocellular carcinoma. Although regulation of cytosolic calcium is essential for HBV replication and is mediated by HBx protein, the mechanism of HBx protein regulating intracellular calcium level remains poorly understood. The present study examined whether HBx protein elevated the intracellular calcium through interacting with storeoperated calcium entry (SOCE) components, Orail and stromal interaction molecule 1, and then identified the targets of HBx protein, with an attempt to understand the mechanism of HBx protein upsetting intracellular calcium homeostasis. By employing co-immunoprecipitation and GST-pull-down assay, we found that Orail protein interacted with HBx protein, and the C-terminus of Orail was implicated in the interaction. Confocal microscopy also revealed that HBx protein could co-localize with full-length Orail protein in HEK293 cells. Moreover, live cell calcium imaging exhibited that HBx protein elevated intracellular calcium, possibly by binding to SOCE components. Our results suggest that HBx protein binds to STIM1-Orail complexes to positively regulate the activity of plasma membrane store-operated calcium channels.

Role of the PI3K‑AKT‑mTOR pathway in hepatitis B virus infection and replication

The replication of hepatitis B virus (HBV) may be modulated by a variety of cell signaling pathways, including the phosphatidylinositol 3‑kinase (PI3K)‑RAC‑α serine/threonine‑protein kinase (AKT)‑serine/threonine‑protein kinase mTOR (mTOR) pathway. The aim of the present study was to determine the regulatory effects of this pathway on the infection and replication of HBV. The results indicated that the HBV entry process may activate the AKT pathway, as demonstrated by AKT phosphorylation in HBV natural infection. However, inhibition of AKT phosphorylation by short‑term treatment with AKT inhibitors was unable to block HBV entry, which suggested that AKT activation induced by HBV infection is not essential for viral entry process. Prolonged treatment with PI3K‑AKT‑mTOR pathway inhibitors markedly promoted HBV replication in HBV replicating and natural infection models. The PI3K‑AKT‑mTOR pathway was therefore identified to be a negative regulator of HBV replication. These inhibitors enhanced the replication and transcription of HBV in an HBx‑dependent way. The results additionally indicated that a PI3K inhibitor, Ly294002, inhibited the secretion of the small surface antigen of HBV in a PI3K‑AKT‑independent manner. The inhibitor Ly294002 may be used as a tool for the drug development of surface antigen secretion inhibitors.

Hepatitis B virus X protein modulates cytosolic Ca2+ signaling in primary human hepatocytes

Worldwide, approximately 240 million people are chronically infected with the hepatitis B virus (HBV); chronic HBV infection is associated with the development of life-threatening liver diseases. The HBV HBx protein alters hepatocyte physiology to promote HBV replication. We previously reported that HBx modulates calcium signaling to stimulate HBV replication in human hepatoblastoma HepG2 cells and primary rat hepatocytes. Whether HBx modulates calcium signaling in a primary human hepatocyte, the natural site of an HBV infection, has not been determined. Here, we report the effect of HBx on calcium signaling in primary human hepatocytes and show that HBx modulates calcium signaling via enhanced calcium entry through store-operated calcium channels and elevated mitochondrial calcium, similar to HBx effects in HepG2 cells and primary rat hepatocytes. In addition to demonstrating that HBV and HBx affect calcium signaling in human hepatocytes, these studies also show that HBV and HBx regulation of calcium signaling is identical in primary human and rat hepatocytes, further validating the use of cultured primary rat hepatocytes for HBV studies.

Mutant p53 Gains Its Function via c-Myc Activation upon CDK4 Phosphorylation at Serine 249 and Consequent PIN1 Binding

TP53 missense mutations significantly influence the development and progression of various human cancers via their gain of new functions (GOF) through different mechanisms. Here we report a unique mechanism underlying the GOF of p53-R249S (p53-RS), a p53 mutant frequently detected in human hepatocellular carcinoma (HCC) that is highly related to hepatitis B infection and aflatoxin B1. A CDK inhibitor blocks p53-RS's nuclear translocation in HCC, whereas CDK4 interacts with p53-RS in the G1/S phase of the cells, phosphorylates it, and enhances its nuclear localization. This is coupled with binding of a peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) to p53-RS, but not the p53 form with mutations of four serines/threonines previously shown to be crucial for PIN1 binding. As a result, p53-RS interacts with c-Myc and enhances c-Myc-dependent rDNA transcription key for ribosomal biogenesis. These results unveil a CDK4-PIN1-p53-RS-c-Myc pathway as a novel mechanism for the GOF of p53-RS in HCC.

Repurposing of Kinase Inhibitors as Broad-Spectrum Antiviral Drugs

The high cost of drug development and the narrow spectrum of coverage typically provided by direct-acting antivirals limit the scalability of this antiviral approach. This review summarizes progress and challenges in the repurposing of approved kinase inhibitors as host-targeted broad-spectrum antiviral therapies.

Virus-host interplay in hepatitis B virus infection and epigenetic treatment strategies

Worldwide, chronic hepatitis B virus (HBV) infection is a major health problem and no cure exists. Importantly, hepatocyte intrusion by HBV particles results in a complex deregulation of both viral and host cellular genetic and epigenetic processes. Among the attempts to develop novel therapeutic approaches against HBV infection, several options targeting the epigenomic regulation of HBV replication are gaining attention. These include the experimental treatment with 'epidrugs'. Moreover, as a targeted approach, the principle of 'epigenetic editing' recently is being exploited to control viral replication. Silencing of HBV by specific rewriting of epigenetic marks might diminish viral replication, viremia, and infectivity, eventually controlling the disease and its complications. Additionally, epigenetic editing can be used as an experimental tool to increase our limited understanding regarding the role of epigenetic modifications in viral infections. Aiming for permanent epigenetic reprogramming of the viral genome without unspecific side effects, this breakthrough may pave the roads for an ambitious technological pursuit: to start designing a curative approach utilizing manipulative molecular therapies for viral infections in vivo.

Hepatitis B virus modulates store-operated calcium entry to enhance viral replication in primary hepatocytes

Many viruses modulate calcium (Ca²⁺) signaling to create a cellular environment that is more permissive to viral replication, but for most viruses that regulate Ca²⁺ signaling, the mechanism underlying this regulation is not well understood. The hepatitis B virus (HBV) HBx protein modulates cytosolic Ca²⁺ levels to stimulate HBV replication in some liver cell lines. A chronic HBV infection is associated with life-threatening liver diseases, including hepatocellular carcinoma (HCC), and HBx modulation of cytosolic Ca²⁺ levels could have an important role in HBV pathogenesis. Whether HBx affects cytosolic Ca²⁺ in a normal hepatocyte, the natural site of an HBV infection, has not been addressed. Here, we report that HBx alters cytosolic Ca²⁺ signaling in cultured primary hepatocytes. We used single cell Ca²⁺ imaging of cultured primary rat hepatocytes to demonstrate that HBx elevates the cytosolic Ca²⁺ level in hepatocytes following an IP₃-linked Ca²⁺ response; HBx effects were similar when expressed alone or in the context of replicating HBV. HBx elevation of the cytosolic Ca²⁺ level required extracellular Ca²⁺ influx and store-operated Ca²⁺ (SOC) entry and stimulated HBV replication in hepatocytes. We used both targeted RT-qPCR and transcriptome-wide RNAseq analyses to compare levels of SOC channel components and other Ca²⁺ signaling regulators in HBV-expressing and control hepatocytes and show that the transcript levels of these various proteins are not affected by HBV. We also show that HBx regulation of SOC-regulated Ca²⁺ accumulation is likely the consequence of HBV modulation of a SOC channel regulatory mechanism. In support of this, we link HBx enhancement of SOC-regulated Ca²⁺ accumulation to Ca²⁺ uptake by mitochondria and demonstrate that HBx stimulates mitochondrial Ca²⁺ uptake in primary hepatocytes. The results of our study may provide insights into viral mechanisms that affect Ca²⁺ signaling to regulate viral replication and virus-associated diseases.

Tissue- and Serum-Associated Biomarkers of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), one of the leading causes of cancer deaths in the world, is offering a challenge to human beings, with the current modes of treatment being a palliative approach. Lack of proper curative or preventive treatment methods encouraged extensive research around the world with an aim to detect a vaccine or therapeutic target biomolecule that could lead to development of a drug or vaccine against HCC. Biomarkers or biological disease markers have emerged as a potential tool as drug/vaccine targets, as they can accurately diagnose, predict, and even prevent the diseases. Biomarker expression in tissue, serum, plasma, or urine can detect tumor in very early stages of its development and monitor the cancer progression and also the effect of therapeutic interventions. Biomarker discoveries are driven by advanced techniques, such as proteomics, transcriptomics, whole genome sequencing, micro- and micro-RNA arrays, and translational clinics. In this review, an overview of the potential of tissue- and serum-associated HCC biomarkers as diagnostic, prognostic, and therapeutic targets for drug development is presented. In addition, we highlight recently developed micro-RNA, long noncoding RNA biomarkers, and single-nucleotide changes, which may be used independently or as complementary biomarkers. These active investigations going on around the world aimed at conquering HCC might show a bright light in the near future.

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.

Intrinsic hepatocyte dedifferentiation is accompanied by upregulation of mesenchymal markers, protein sialylation and core alpha 1,6 linked fucosylation

Alterations in N-linked glycosylation have long been associated with cancer but for the most part, the reasons why have remained poorly understood. Here we show that increased core fucosylation is associated with de-differentiation of primary hepatocytes and with the appearance of markers indicative of a transition of cells from an epithelial to a mesenchymal state. This increase in core fucosylation was associated with increased levels of two enzymes involved in α-1,6 linked fucosylation, GDP-mannose 4, 6-dehydratase (Gmds) and to a lesser extent fucosyltransferase 8 (Fut8). In addition, the activation of cancer-associated cellular signaling pathways in primary rat hepatocytes can increase core fucosylation and induce additional glycoform alterations on hepatocyte proteins. Specifically, we show that increased levels of protein sialylation and α-1,6-linked core fucosylation are observed following activation of the β-catenin pathway. Activation of the Akt signaling pathway or induction of hypoxia also results in increased levels of fucosylation and sialylation. We believe that this knowledge will help in the better understanding of the genetic factors associated with altered glycosylation and may allow for the development of more clinically relevant biomarkers.

CYP2C19 Genotype Could be a Predictive Factor for Aggressive Manifestations of Hepatocellular Carcinoma Related with Chronic Hepatitis B Infection in Thailand

BACKGROUND

Chronic hepatitis B virus (HBV) infection related hepatocellular carcinoma (HCC) is a major health problem in the Asia-Pacific region including Thailand. Several factors have been proposed as contributing to hepatocarcinogenesis. This study was aimed to investigate the impact of CYP2C19 genotypic polymorphism in HCC related to chronic HBV infection in Thailand.

MATERIALS AND METHODS

A cross-sectional study was performed between April 2014 and January 2015. Chronic HBV patients with HCC (n=50) and without HCC (n=50) were included. Clinical information and blood samples of all patients were collected. The CYP2C19 genotype was determined by polymerase chain reaction-restriction fragment length polymorphism method, and was classified as rapid metabolizer (RM), intermediate metabolizer (IM) or poor metabolizer (PM).

RESULTS

The CYP2C19 genotype frequencies of RM, IM and PM in HBV patients were found to be 19/50 (38%), 25/50 (50%) and 6/50 (12%), respectively. The CYP2C19 genotype frequencies of RM, IM and PM in HBV with HCC patients were 21/50 (42%), 25/50 (50%) and 4/50 (8%), respectively. The distribution of CYP2C19 genotype was not different between patients with and without HCC. Interestingly, among HBV with HCC patients, the RM genotype of CYP2C19 tended to increase risk of aggressive manifestation (OR=2.89, 95%CI=0.76-11.25, P-value = 0.07), compared with non RM genotype carriers.

CONCLUSIONS

CYP2C19 genotype IM was the most common genotype in Thai patients with chronic HBV infection. In addition, genotype RM could be an associated factor for aggressive presentation in HCC related to chronic HBV infection.

Transcriptome-Wide Analysis of Hepatitis B Virus-Mediated Changes to Normal Hepatocyte Gene Expression

Globally, a chronic hepatitis B virus (HBV) infection remains the leading cause of primary liver cancer. The mechanisms leading to the development of HBV-associated liver cancer remain incompletely understood. In part, this is because studies have been limited by the lack of effective model systems that are both readily available and mimic the cellular environment of a normal hepatocyte. Additionally, many studies have focused on single, specific factors or pathways that may be affected by HBV, without addressing cell physiology as a whole. Here, we apply RNA-seq technology to investigate transcriptome-wide, HBV-mediated changes in gene expression to identify single factors and pathways as well as networks of genes and pathways that are affected in the context of HBV replication. Importantly, these studies were conducted in an ex vivo model of cultured primary hepatocytes, allowing for the transcriptomic characterization of this model system and an investigation of early HBV-mediated effects in a biologically relevant context. We analyzed differential gene expression within the context of time-mediated gene-expression changes and show that in the context of HBV replication a number of genes and cellular pathways are altered, including those associated with metabolism, cell cycle regulation, and lipid biosynthesis. Multiple analysis pipelines, as well as qRT-PCR and an independent, replicate RNA-seq analysis, were used to identify and confirm differentially expressed genes. HBV-mediated alterations to the transcriptome that we identified likely represent early changes to hepatocytes following an HBV infection, suggesting potential targets for early therapeutic intervention. Overall, these studies have produced a valuable resource that can be used to expand our understanding of the complex network of host-virus interactions and the impact of HBV-mediated changes to normal hepatocyte physiology on viral replication.

Hepatitis B Virus X and Regulation of Viral Gene Expression

The efficient replication of hepatitis B virus (HBV) requires the HBV regulatory hepatitis B virus X (HBx) protein. The exact contributions of HBx are not fully understood, in part because of the limitations of the assays used for its study. When HBV replication is driven from a plasmid DNA, the contribution of HBx is modest. However, there is an absolute requirement for HBx in assays that recapitulate the infectious virus life cycle. There is much evidence that HBx can contribute directly to HBV replication by acting on viral promoters embedded within protein coding sequences. In addition, HBx may also contribute indirectly by modulating cellular pathways to benefit virus replication. Understanding the mechanism(s) of HBx action during virus replication may provide insight into novel ways to disrupt chronic HBV replication.

Interstitial Fluid Flow Increases Hepatocellular Carcinoma Cell Invasion through CXCR4/CXCL12 and MEK/ERK Signaling

Hepatocellular carcinoma (HCC) is the most common form of liver cancer (~80%), and it is one of the few cancer types with rising incidence in the United States. This highly invasive cancer is very difficult to detect until its later stages, resulting in limited treatment options and low survival rates. There is a dearth of knowledge regarding the mechanisms associated with the effects of biomechanical forces such as interstitial fluid flow (IFF) on hepatocellular carcinoma invasion. We hypothesized that interstitial fluid flow enhanced hepatocellular carcinoma cell invasion through chemokine-mediated autologous chemotaxis. Utilizing a 3D in vitro invasion assay, we demonstrated that interstitial fluid flow promoted invasion of hepatocellular carcinoma derived cell lines. Furthermore, we showed that autologous chemotaxis influences this interstitial fluid flow-induced invasion of hepatocellular carcinoma derived cell lines via the C-X-C chemokine receptor type 4 (CXCR4)/C-X-C motif chemokine 12 (CXCL12) signaling axis. We also demonstrated that mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling affects interstitial fluid flow-induced invasion; however, this pathway was separate from CXCR4/CXCL12 signaling. This study demonstrates, for the first time, the potential role of interstitial fluid flow in hepatocellular carcinoma invasion. Uncovering the mechanisms that control hepatocellular carcinoma invasion will aid in enhancing current liver cancer therapies and provide better treatment options for patients.

Hepatitis B virus and microRNAs: Complex interactions affecting hepatitis B virus replication and hepatitis B virus-associated diseases

Chronic infection with the hepatitis B virus (HBV) is the leading risk factor for the development of hepatocellular carcinoma (HCC). With nearly 750000 deaths yearly, hepatocellular carcinoma is the second highest cause of cancer-related death in the world. Unfortunately, the molecular mechanisms that contribute to the development of HBV-associated HCC remain incompletely understood. Recently, microRNAs (miRNAs), a family of small non-coding RNAs that play a role primarily in post-transcriptional gene regulation, have been recognized as important regulators of cellular homeostasis, and altered regulation of miRNA expression has been suggested to play a significant role in virus-associated diseases and the development of many cancers. With this in mind, many groups have begun to investigate the relationship between miRNAs and HBV replication and HBV-associated disease. Multiple findings suggest that some miRNAs, such as miR-122, and miR-125 and miR-199 family members, are playing a role in HBV replication and HBV-associated disease, including the development of HBV-associated HCC. In this review, we discuss the current state of our understanding of the relationship between HBV and miRNAs, including how HBV affects cellular miRNAs, how these miRNAs impact HBV replication, and the relationship between HBV-mediated miRNA regulation and HCC development. We also address the impact of challenges in studying HBV, such as the lack of an effective model system for infectivity and a reliance on transformed cell lines, on our understanding of the relationship between HBV and miRNAs, and propose potential applications of miRNA-related techniques that could enhance our understanding of the role miRNAs play in HBV replication and HBV-associated disease, ultimately leading to new therapeutic options and improved patient outcomes.