Hypermethylation of the glutathione peroxidase 4 gene promoter is associated with the occurrence of immune tolerance phase in chronic hepatitis B.

BACKGROUND: Hepatitis B virus (HBV) infection is a public health problem that seriously threatens human health. This study aimed to investigate the clinical significance of glutathione peroxidase 4(GPX4) in the occurrence and development of chronic hepatitis B (CHB). METHODS: A total of 169 participants including 137 patients with CHB and 32 healthy controls (HCs) were recruited. We detected the expression of GPX4 and stimulator of interferon genes (STING) in peripheral blood mononuclear cells (PBMCs) by real-time quantitative polymerase chain reaction (RT-qPCR). The methylation level of GPX4 gene promoter in PBMCs was detected by TaqMan probe-based quantitative methylation-specific PCR (MethyLight). Enzyme-linked immunosorbent assay (ELISA) was performed to detect the serum levels of GPX4, IFN-ß, oxidative stress (OS) related molecules, and pro-inflammatory cytokines. RESULTS: The expression levels of GPX4 in PBMCs and serum of CHB patients were lower than those of HCs, but the methylation levels of GPX4 promoter were higher than those of HCs, especially in patients at the immune tolerance phase. STING mRNA expression levels in PBMCs and serum IFN-ß levels of patients at the immune activation phase and reactivation phase of CHB were higher than those at other clinical phases of CHB and HCs. GPX4 mRNA expression level and methylation level in PBMCs from patients with CHB had a certain correlation with STING and IFN-ß expression levels. In addition, the methylation level of the GPX4 promoter in PBMCs from patients with CHB was correlated with molecules associated with OS and inflammation. CONCLUSIONS: GPX4 may play an important role in the pathogenesis and immune tolerance of CHB, which may provide new ideas for the functional cure of CHB.

Class A capsid assembly modulator apoptotic elimination of hepatocytes with high HBV core antigen level in vivo is dependent on de novo core protein translation.

Capsid assembly is critical in the hepatitis B virus (HBV) life cycle, mediated by the viral core protein. Capsid assembly is the target for new anti-viral therapeutics known as capsid assembly modulators (CAMs) of which the CAM-aberrant (CAM-A) class induces aberrant shaped core protein structures and leads to hepatocyte cell death. This study aimed to identify the mechanism of action of CAM-A modulators leading to HBV-infected hepatocyte elimination where CAM-A-mediated hepatitis B surface antigen (HBsAg) reduction was evaluated in a stable HBV replicating cell line and in AAV-HBV-transduced C57BL/6, C57BL/6 SCID, and HBV-infected chimeric mice with humanized livers. Results showed that in vivo treatment with CAM-A modulators induced pronounced reductions in hepatitis B e antigen (HBeAg) and HBsAg, associated with a transient alanine amino transferase (ALT) increase. Both HBsAg and HBeAg reductions and ALT increase were delayed in C57BL/6 SCID and chimeric mice, suggesting that adaptive immune responses may indirectly contribute. However, CD8+ T cell depletion in transduced wild-type mice did not impact antigen reduction, indicating that CD8+ T cell responses are not essential. Transient ALT elevation in AAV-HBV-transduced mice coincided with a transient increase in endoplasmic reticulum stress and apoptosis markers, followed by detection of a proliferation marker. Microarray data revealed antigen presentation pathway (major histocompatibility complex class I molecules) upregulation, overlapping with the apoptosis. Combination treatment with HBV-specific siRNA demonstrated that CAM-A-mediated HBsAg reduction is dependent on de novo core protein translation. To conclude, CAM-A treatment eradicates HBV-infected hepatocytes with high core protein levels through the induction of apoptosis, which can be a promising approach as part of a regimen to achieve functional cure. IMPORTANCE: Treatment with hepatitis B virus (HBV) capsid assembly modulators that induce the formation of aberrant HBV core protein structures (CAM-A) leads to programmed cell death, apoptosis, of HBV-infected hepatocytes and subsequent reduction of HBV antigens, which differentiates CAM-A from other CAMs. The effect is dependent on the de novo synthesis and high levels of core protein.

Oxygen-dependent histone lysine demethylase 4 restricts hepatitis B virus replication.

Mammalian cells have evolved strategies to regulate gene expression when oxygen is limited. Hypoxia-inducible factors (HIF) are the major transcriptional regulators of host gene expression. We previously reported that HIFs bind and activate hepatitis B virus (HBV) DNA transcription under low oxygen conditions; however, the global cellular response to low oxygen is mediated by a family of oxygenases that work in concert with HIFs. Recent studies have identified a role for chromatin modifiers in sensing cellular oxygen and orchestrating transcriptional responses, but their role in the HBV life cycle is as yet undefined. We demonstrated that histone lysine demethylase 4 (KDM4) can restrict HBV, and pharmacological or oxygen-mediated inhibition of the demethylase increases viral RNAs derived from both episomal and integrated copies of the viral genome. Sequencing studies demonstrated that KDM4 is a major regulator of the hepatic transcriptome, which defines hepatocellular permissivity to HBV infection. We propose a model where HBV exploits cellular oxygen sensors to replicate and persist in the liver. Understanding oxygen-dependent pathways that regulate HBV infection will facilitate the development of physiologically relevant cell-based models that support efficient HBV replication.

Hepatitis B virus RNAs co-opt ELAVL1 for stabilization and CRM1-dependent nuclear export.

Hepatitis B virus (HBV) chronically infects 296 million people worldwide, posing a major global health threat. Export of HBV RNAs from the nucleus to the cytoplasm is indispensable for viral protein translation and genome replication, however the mechanisms regulating this critical process remain largely elusive. Here, we identify a key host factor embryonic lethal, abnormal vision, Drosophila-like 1 (ELAVL1) that binds HBV RNAs and controls their nuclear export. Using an unbiased quantitative proteomics screen, we demonstrate direct binding of ELAVL1 to the HBV pregenomic RNA (pgRNA). ELAVL1 knockdown inhibits HBV RNAs posttranscriptional regulation and suppresses viral replication. Further mechanistic studies reveal ELAVL1 recruits the nuclear export receptor CRM1 through ANP32A and ANP32B to transport HBV RNAs to the cytoplasm via specific AU-rich elements, which can be targeted by a compound CMLD-2. Moreover, ELAVL1 protects HBV RNAs from DIS3+RRP6+ RNA exosome mediated nuclear RNA degradation. Notably, we find HBV core protein is dispensable for HBV RNA-CRM1 interaction and nuclear export. Our results unveil ELAVL1 as a crucial host factor that regulates HBV RNAs stability and trafficking. By orchestrating viral RNA nuclear export, ELAVL1 is indispensable for the HBV life cycle. Our study highlights a virus-host interaction that may be exploited as a new therapeutic target against chronic hepatitis B.

Structural Insights into the Interaction between the C-Terminal-Deleted BH3-like Motif Peptide of Hepatitis B Virus X Protein and Bcl-xL.

Hepatitis B virus X protein (HBx) plays a crucial role in the development of hepatocellular carcinoma (HCC) associated with hepatitis B virus (HBV) infection. The full-length HBx protein interacts with Bcl-xL and is involved in the HBV replication and cell death processes. The three hydrophobic residues Trp120, Leu123, and Ile127 of the HBx BH3-like motif are essential for the Bcl-xL-binding. On the other hand, various lengths of C-terminal-truncated HBx mutants are frequently detected in HCC tissues, and these mutants, rather than the full-length HBx, appear to be responsible for HCC development. Notably, the region spanning residues 1-120 of HBx [HBx(1 and 120)] has been strongly associated with an increased risk of HCC development. However, the mode of interaction between HBx(1-120) and Bcl-xL remains unclear. HBx(1-120) possesses only Trp120 among the three hydrophobic residues essential for the Bcl-xL-binding. To elucidate this interaction mode, we employed a C-terminal-deleted HBx BH3-like motif peptide composed of residues 101-120. Here, we present the NMR complex structure of Bcl-xL and HBx(101-120). Our results demonstrate that HBx(101-120) binds to Bcl-xL in a weaker manner. Considering the high expression of Bcl-xL in HCC cells, this weak interaction, in conjunction with the overexpression of Bcl-xL in HCC cells, may potentially contribute to HCC development through the interaction between C-terminal-truncated HBx and Bcl-xL.

SRPK2 Mediates HBV Core Protein Phosphorylation and Capsid Assembly via Docking Interaction.

Members of the serine-arginine protein kinase (SRPK) family, SRPK1 and SRPK2, phosphorylate the hepatitis B core protein (Cp) and are crucial for pregenomic RNA encapsidation during viral nucleocapsid assembly. Among them, SRPK2 exhibits higher kinase activity toward Cp. In this study, we identified Cp sites that are phosphorylated by SRPK2 and demonstrated that the kinase utilizes an SRPK-specific docking groove to interact with and regulate the phosphorylation of the C-terminal arginine rich domain of Cp. We determined that direct interaction between the docking groove of SRPK2 and unphosphorylated Cp inhibited premature viral capsid assembly in vitro, whereas the phosphorylation of the viral protein reactivated the process. Pull-down assays together with the new cryo-electron microscopy structure of the HBV capsid in complex with SRPK2 revealed that the kinases decorate the surface of the viral capsid by interacting with the C-terminal domain of Cp, underscoring the importance of the docking interaction in regulating capsid assembly and pregenome packaging. Moreover, SRPK2-knockout in HepG2 cells suppressed Cp phosphorylation, indicating that SRPK2 is an important cellular kinase for HBV life cycle.

Ten-eleven translocation (Tet) methylcytosine dioxygenase-dependent viral DNA demethylation mediates in vivo hepatitis B virus (HBV) biosynthesis.

Liver-specific ten-eleven translocation (Tet) methylcytosine dioxygenases 2 and 3 (Tet2 plus Tet3)-deficient hepatitis B virus (HBV) transgenic mice fail to support viral biosynthesis. The levels of viral transcription and replication intermediates are dramatically reduced. Hepatitis B core antigen is only observed in a very limited number of pericentral hepatocytes in a pattern that is similar to glutamate-ammonia ligase (Glul), a ß-catenin target gene. HBV transcript abundance in adult Tet-deficient mice resembles that observed in wild-type neonatal mice. Furthermore, the RNA levels of several ß-catenin target genes including Glul, Lhpp, Notun, Oat, Slc1a2, and Tbx3 in Tet-deficient mice were also similar to that observed in wild-type neonatal mice. As HBV transcription is regulated by ß-catenin, these findings support the suggestion that neonatal Tet deficiency might limit ß-catenin target gene expression, limiting viral biosynthesis. Additionally, HBV transgene DNA displays increased 5-methylcytosine (5mC) frequency at CpG sequences consistent with neonatal Tet deficiency being responsible for decreased developmental viral DNA demethylation mediated by 5mC oxidation to 5-hydroxymethylcytosine, a process that might be responsible for the reduction in cellular ß-catenin target gene expression and viral transcription and replication.IMPORTANCEChronic hepatitis B virus (HBV) infection causes significant worldwide morbidity and mortality. There are no curative therapies available to resolve chronic HBV infections, and the small viral genome limits molecular targets for drug development. An alternative approach to drug development is to target cellular genes essential for HBV biosynthesis. In the liver, ten-eleven translocation (Tet) genes encode cellular enzymes that are not essential for postnatal mouse development but represent essential activities for viral DNA demethylation and transcription. Consequently, Tet inhibitors may potentially be developed into therapeutic agents capable of inducing and/or maintaining HBV covalently closed circular DNA methylation, resulting in transcriptional silencing and the resolution of chronic viral infection.

The N6-methyladenosine demethylase ALKBH5 regulates the hypoxic HBV transcriptome.

Chronic hepatitis B is a global health problem and current treatments only suppress hepatitis B virus (HBV) infection, highlighting the need for new curative treatments. Oxygen levels influence HBV replication and we previously reported that hypoxia inducible factors (HIFs) activate the basal core promoter (BCP). Here we show that the hypoxic-dependent increase in BCP-derived transcripts is dependent on N6-methyladenosine (m6A) modifications in the 5' stem loop that regulate RNA half-life. Application of a probe-enriched long-read sequencing method to accurately map the HBV transcriptome showed an increased abundance of pre-genomic RNA under hypoxic conditions. Mapping the transcription start sites of BCP-RNAs identified a role for hypoxia to regulate pre-genomic RNA splicing that is dependent on m6A modification. Bioinformatic analysis of published single cell RNA-seq of murine liver showed an increased expression of the RNA demethylase ALKBH5 in the peri-central low oxygen region. In vitro studies with a human hepatocyte derived HepG2-NTCP cell line showed increased ALKBH5 gene expression under hypoxic conditions and a concomitant reduction in m6A-modified HBV BCP-RNA and host RNAs. Silencing the demethylase reduced the level of BCP-RNAs and host gene (CA9, NDRG1, VEGFA, BNIP3, FUT11, GAP and P4HA1) transcripts and this was mediated via reduced HIFα expression. In summary, our study highlights a previously unrecognized role for ALKBH5 in orchestrating viral and cellular transcriptional responses to low oxygen.

Genome-wide loss-of-function genetic screen identifies INSIG2 as the vulnerability of hepatitis B virus-integrated hepatoma cells.

There are approximately 250 million people chronically infected with hepatitis B virus (HBV) worldwide. Although HBV is often integrated into the host genome and promotes hepatocarcinogenesis, vulnerability of HBV integration in liver cancer cells has not been clarified. The aim of our study is to identify vulnerability factors for HBV-associated hepatocarcinoma. Loss-of-function screening was undertaken in HepG2 and HBV-integrated HepG2.2.15 cells expressing SpCas9 using a pooled genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) library. Genes whose guide RNA (gRNA) abundance significantly decreased in HepG2.2.15 cells but not in HepG2 cells were extracted using the MAGeCK algorithm. We identified four genes (BCL2L1, VPS37A, INSIG2, and CFLAR) that showed significant reductions of gRNA abundance and thus potentially involved in the vulnerability of HBV-integrated cancer cells. Among them, siRNA-mediated mRNA inhibition or CRISPR-mediated genetic deletion of INSIG2 significantly impaired cell proliferation in HepG2.2.15 cells but not in HepG2 cells. Its inhibitory effect was alleviated by cotransfection of siRNAs targeting HBV. INSIG2 inhibition suppressed the pathways related to cell cycle and DNA replication, downregulated cyclin-dependent kinase 2 (CDK2) levels, and delayed the G1 -to-S transition in HepG2.2.15 cells. CDK2 inhibitor suppressed cell cycle progression in HepG2.2.15 cells and INSIG2 inhibition did not suppress cell proliferation in the presence of CDK2 inhibitor. In conclusion, INSIG2 inhibition induced cell cycle arrest in HBV-integrated hepatoma cells in a CDK2-dependent manner, and thus INSIG2 might be a vulnerability factor for HBV-associated liver cancer.

Hypomethylation of glycine dehydrogenase promoter in peripheral blood mononuclear cells is a new diagnostic marker of hepatitis B virus-associated hepatocellular carcinoma.

BACKGROUND: Glycine dehydrogenase (GLDC) plays an important role in the initiation and proliferation of several human cancers. In this study, we aimed to detect the methylation status of GLDC promoter and its diagnostic value for hepatitis B virus-associated hepatocellular carcinoma (HBV-HCC). METHODS: We enrolled 197 patients, 111 with HBV-HCC, 51 with chronic hepatitis B (CHB), and 35 healthy controls (HCs). The methylation status of GLDC promoter in peripheral mononuclear cells (PBMCs) was identified by methylation specific polymerase chain reaction (MSP). The mRNA expression was examined using real-time quantitative polymerase chain reaction (qPCR). RESULTS: The methylation frequency of the GLDC promoter was significantly lower in HBV-HCC patients (27.0%) compared to that in CHB patients (68.6%) and HCs (74.3%) (P < 0.001). The methylated group had lower alanine aminotransferase level (P = 0.035) and lower rates of tumor node metastasis (TNM) III/IV (P = 0.043) and T3/T4 (P = 0.026). TNM stage was identified to be an independent factor for GLDC promoter methylation. GLDC mRNA levels in CHB patients and HCs were significantly lower than those in HBV-HCC patients (P = 0.022 and P < 0.001, respectively). GLDC mRNA levels were significantly higher in HBV-HCC patients with unmethylated GLDC promoters than those with methylated GLDC promoters (P = 0.003). The diagnostic accuracy of alpha-fetoprotein (AFP) combined with GLDC promoter methylation for HBV-HCC was improved compared with that of AFP alone (AUC: 0.782 vs. 0.630, P < 0.001). In addition, GLDC promoter methylation was an independent predictor for overall survival of HBV-HCC patients (P = 0.038). CONCLUSIONS: The methylation frequency of GLDC promoter was lower in PBMCs from HBV-HCC patients than that from patients with CHB and HCs. The combination of AFP and GLDC promoter hypomethylation significantly improved the diagnostic accuracy of HBV-HCC.

Engineered extracellular vesicles for delivering functional Cas9/gRNA to eliminate hepatitis B virus cccDNA and integration.

The persistence of HBV covalently closed circular DNA (cccDNA) and HBV integration into the host genome in infected hepatocytes pose significant challenges to the cure of chronic HBV infection. Although CRISPR/Cas9-mediated genome editing shows promise for targeted clearance of viral genomes, a safe and efficient delivery method is currently lacking. Here, we developed a novel approach by combining light-induced heterodimerization and protein acylation to enhance the loading efficiency of Cas9 protein into extracellular vesicles (EVs). Moreover, vesicular stomatitis virus-glycoprotein (VSV-G) was incorporated onto the EVs membrane, significantly facilitating the endosomal escape of Cas9 protein and increasing its gene editing activity in recipient cells. Our results demonstrated that engineered EVs containing Cas9/gRNA and VSV-G can effectively reduce viral antigens and cccDNA levels in the HBV-replicating and infected cell models. Notably, we also confirmed the antiviral activity and high safety of the engineered EVs in the HBV-replicating mouse model generated by hydrodynamic injection and the HBV transgenic mouse model. In conclusion, engineered EVs could successfully mediate functional CRISPR/Cas9 delivery both in vitro and in vivo, leading to the clearance of episomal cccDNA and integrated viral DNA fragments, and providing a novel therapeutic approach for curing chronic HBV infection.

Serum exosomes from hepatitis B virus-infected patients inhibit glycolysis in Sertoli cells via miR-122-5p/ALDOA axis.

Hepatitis B virus (HBV) infection is associated with male infertility. The mechanism includes an increase in chromosomal instability in sperm, which has an adverse effect on sperm viability and function. Sertoli cells (SCs) are vital in spermatogenesis because they use glycolysis to provide energy to germ cells and themselves. HBV infection impairs sperm function. However, whether HBV infection disrupts energy metabolism in SCs remains unclear. This study aimed to determine the role of serum exosomes of HBV-infected patients in SC viability and glycolysis. Serum exosomes were obtained from 30 patients with (HBV+_exo) or without (HBV-_exo) HBV infection using high-speed centrifugation and identified by transmission electron microscopy and western blot analysis. Cell viability is determined by CCK-8 assay. Glycolysis is determined by detecting extracellular acidification rate and ATP levels. miR-122-5p expression levels are detected by quantitative RT-PCR, and a dual-luciferase gene reporter assay confirms the downstream target gene of miR-122-5p. Protein expression is determined by western blot analysis. The results show that HBV+ _exo inhibited cell viability, extracellular acidification rate, and ATP production of SCs. miR-122-5p is highly expressed in HBV+ _exo compared with that in HBV-_exo. Furthermore, HBV+ _exo is efficiently taken up by SCs, whereas miR-122-5p is efficiently transported to SCs. miR-122-5p overexpression downregulates ALDOA expression and inhibits SC viability and glycolysis. However, ALDOA overexpression reverses the effects of miR-122-5p and HBV+ _exo on SC viability and glycolysis. HBV+ _exo may deliver miR-122-5p to target ALDOA and inhibit SC viability and glycolysis, thus providing new therapeutic ideas for treating HBV-associated male infertility.

Hepatitis B Virus Modulated Transcriptional Regulatory Map of Hepatic Cellular MicroRNAs.

Hepatitis B virus (HBV) is an enveloped, hepatotropic, noncytopathic virus with a partially double-stranded DNA genome. It infects hepatocytes and is associated with progression to liver fibrosis and cirrhosis, culminating in hepatocellular carcinoma (HCC), accounting for 55% of total HCC cases. MicroRNAs (miRNAs) regulated by HBV play an important role in these pathologies. Mapping the miRNAs responsive to HBV and HBV-specific proteins, including HBV X protein (HBx) that harbor the majority of HBV-human protein interactions, could aid accelerate the diagnostics and therapeutics innovation against the infection and associated diseases. With this in mind, we used a unique annotation strategy whereby we first amassed 362 mature HBV responsive-human Differentially Expressed miRNAs (HBV-hDEmiRs). The core experimentally-validated messenger RNA targets of the HBV-hDEmiRs were mostly associated with viral infections and hepatic inflammation processes. Moreover, our annotation strategy enabled the characterization of HBx-dependent/independent HBV-hDEmiRs as a tool for evaluation of the impact of HBx as a therapeutic target. Bioinformatics analysis of the HBV-human protein-protein interactome revealed new insights into the transcriptional regulatory network of the HBV-hDEmiRs. We performed a comparative analysis of data on miRNAs gathered from HBV infected cell line studies and from tissue studies of fibrosis, cirrhosis, and HCC. Accordingly, we propose hsa-miR-15a-5p that is downregulated by multiple HBV proteins, including HBx, as a potential biomarker of HBV infection, and its progression to HCC. In all, this study underscores (1) the complexity of miRNA regulation in response to HBV infection and its progression into other liver pathologies and (2) provides a regulatory map of HBV-hDEmiRs and the underlying mechanisms modulating their expression through a cross talk between HBV viral proteins and human transcription factors.

Recent Advances in the Development of Sulfamoyl-Based Hepatitis B Virus Nucleocapsid Assembly Modulators.

Hepatitis B virus (HBV) is the primary contributor to severe liver ailments, encompassing conditions such as cirrhosis and hepatocellular carcinoma. Globally, 257 million people are affected by HBV annually and 887,000 deaths are attributed to it, representing a substantial health burden. Regrettably, none of the existing therapies for chronic hepatitis B (CHB) have achieved satisfactory clinical cure rates. This issue stems from the existence of covalently closed circular DNA (cccDNA), which is difficult to eliminate from the nucleus of infected hepatocytes. HBV genetic material is composed of partially double-stranded DNA that forms complexes with viral polymerase inside an icosahedral capsid composed of a dimeric core protein. The HBV core protein, consisting of 183 to 185 amino acids, plays integral roles in multiple essential functions within the HBV replication process. In this review, we describe the effects of sulfamoyl-based carboxamide capsid assembly modulators (CAMs) on capsid assembly, which can suppress HBV replication and disrupt the production of new cccDNA. We present research on classical, first-generation sulfamoyl benzocarboxamide CAMs, elucidating their structural composition and antiviral efficacy. Additionally, we explore newly identified sulfamoyl-based CAMs, including sulfamoyl bicyclic carboxamides, sulfamoyl aromatic heterocyclic carboxamides, sulfamoyl aliphatic heterocyclic carboxamides, cyclic sulfonamides, and non-carboxamide sulfomoyl-based CAMs. We believe that certain molecules derived from sulfamoyl groups have the potential to be developed into essential components of a well-suited combination therapy, ultimately yielding superior clinical efficacy outcomes in the future.

Gene-Editing and RNA Interference in Treating Hepatitis B: A Review.

The hepatitis B virus (HBV) continues to cause substantial health and economic burdens, and its target of elimination may not be reached in 2030 without further efforts in diagnostics, non-pharmaceutical prevention measures, vaccination, and treatment. Current therapeutic options in chronic HBV, based on interferons and/or nucleos(t)ide analogs, suppress the virus replication but do not eliminate the pathogen and suffer from several constraints. This paper reviews the progress on biotechnological approaches in functional and definitive HBV treatments, including gene-editing tools, i.e., zinc-finger proteins, transcription activator-like effector nucleases, and CRISPR/Cas9, as well as therapeutics based on RNA interference. The advantages and challenges of these approaches are also discussed. Although the safety and efficacy of gene-editing tools in HBV therapies are yet to be demonstrated, they show promise for the revitalization of a much-needed advance in the field and offer viral eradication. Particular hopes are related to CRISPR/Cas9; however, therapeutics employing this system are yet to enter the clinical testing phases. In contrast, a number of candidates based on RNA interference, intending to confer a functional cure, have already been introduced to human studies. However, larger and longer trials are required to assess their efficacy and safety. Considering that prevention is always superior to treatment, it is essential to pursue global efforts in HBV vaccination.

SUV39H1 is a novel biomarker targeting oxidative phosphorylation in hepatitis B virus-associated hepatocellular carcinoma.

BACKGROUND: As a histone methyltransferase, suppressor of variegation 3-9 homolog 1 (SUV39H1) plays an important role in the occurrence and development of cancer. To explore the mechanism and biological function of SUV39H1 in hepatitis B virus-associated hepatocellular carcinoma (HBV-HCC) can gain an insight into the pathogenesis of HBV-HCC. METHODS: The effect of HBV infection on SUV39H1 in hepatoma cells was detected. CCK-8, colony growth assay and wound healing assay were used to assess the proliferation and migration of HBV-positive hepatoma cells. RNA sequencing (RNA-seq) was applied to find differential genes and enriched pathways. The serum SUV39H1 level in HBV-HCC patients was detected and its correlation with clinical indicators was analyzed. RESULTS: SUV39H1 was increased by HBV infection and promoted the proliferation and migration of hepatoma cells. SUV39H1 could upregulate the expression of mitochondrial oxidative phosphorylation (OXPHOS) pathway-related genes. OXPHOS pathway inhibitors could reduce the capacity of proliferation and migration of hepatoma cells after overexpressing SUV39H1. Serum SUV39H1 levels were higher in chronic hepatitis B (CHB) patients than in healthy controls and higher in HBV-HCC patients than in CHB patients. In the diagnosis of HCC, the predictive value of SUV39H1 combined with alpha-fetoprotein (AFP) was better than that of AFP alone. CONCLUSION: SUV39H1 is regulated by HBV infection and promotes the proliferation and migration of hepatoma cells by targeting OXPHOS pathway. It indicates that SUV39H1 may be a new biomarker of the diagnosis of HCC.

Hepatitis B doubly spliced protein (HBDSP) promotes hepatocellular carcinoma cell apoptosis via ETS1/GATA2/YY1-mediated p53 transcription.

IMPORTANCE: Hepatitis B virus (HBV) spliced variants are associated with viral persistence or pathogenicity. Hepatitis B doubly spliced protein (HBDSP), which has been previously reported as a pleiotropic transactivator protein, can potentially serve as an HBV virulence factor. However, the underlying mechanisms of HBDSP in HBV-associated liver diseases remain to be elucidated. In this study, we revealed that HBDSP promotes cellular apoptosis and induces wt-p53-dependent apoptotic signaling pathway in wt-p53 hepatocellular cells by transactivating p53 transcription, and increases the release of HBV progeny. Therefore, HBDSP may promote the HBV particles release through wt-p53-dependent hepatocellular apoptosis. Our findings suggest that blocking HBDSP-induced wt-p53-dependent apoptosis might have therapeutic values for chronic hepatitis B.

Synergism in actions of HBV with aflatoxin in cancer development.

Aflatoxin B1 (AFB1) is a fungal metabolite found in animal feeds and human foods. It is one of the most toxic and carcinogenic of aflatoxins and is classified as a Group 1 carcinogen. Dietary exposure to AFB1 and infection with chronic Hepatitis B Virus (HBV) make up two of the major risk factors for hepatocellular carcinoma (HCC). These two major risk factors raise the probability of synergism between the two agents. This review proposes some collaborative molecular mechanisms underlying the interaction between AFB1 and HBV in accelerating or magnifying the effects of HCC. The HBx viral protein is one of the main viral proteins of HBV and has many carcinogenic qualities that are involved with HCC. AFB1, when metabolized by CYP450, becomes AFB1-exo-8,9-epoxide (AFBO), an extremely toxic compound that can form adducts in DNA sequences and induce mutations. With possible synergisms that exist between HBV and AFB1 in mind, it is best to treat both agents simultaneously to reduce the risk by HCC.

Hepatitis B virus infection disrupts homologous recombination in hepatocellular carcinoma by stabilizing resection inhibitor ADRM1.

Many cancers harbor homologous recombination defects (HRDs). A HRD is a therapeutic target that is being successfully utilized in treatment of breast/ovarian cancer via synthetic lethality. However, canonical HRD caused by BRCAness mutations do not prevail in liver cancer. Here we report a subtype of HRD caused by the perturbation of a proteasome variant (CDW19S) in hepatitis B virus-bearing (HBV-bearing) cells. This amalgamate protein complex contained the 19S proteasome decorated with CRL4WDR70 ubiquitin ligase, and assembled at broken chromatin in a PSMD4Rpn10- and ATM-MDC1-RNF8-dependent manner. CDW19S promoted DNA end processing via segregated modules that promote nuclease activities of MRE11 and EXO1. Contrarily, a proteasomal component, ADRM1Rpn13, inhibited resection and was removed by CRL4WDR70-catalyzed ubiquitination upon commitment of extensive resection. HBx interfered with ADRM1Rpn13 degradation, leading to the imposition of ADRM1Rpn13-dependent resection barrier and consequent viral HRD subtype distinguishable from that caused by BRCA1 defect. Finally, we demonstrated that viral HRD in HBV-associated hepatocellular carcinoma can be exploited to restrict tumor progression. Our work clarifies the underlying mechanism of a virus-induced HRD subtype.

Novel non-HAP class A HBV capsid assembly modulators have distinct in vitro and in vivo profiles.

IMPORTANCE: Chronic hepatitis B is the most important cause of liver cancer worldwide and affects more than 290 million people. Current treatments are mostly suppressive and rarely lead to a cure. Therefore, there is a need for novel and curative drugs that target the host or the causative agent, hepatitis B virus itself. Capsid assembly modulators are an interesting class of antiviral molecules that may one day become part of curative treatment regimens for chronic hepatitis B. Here we explore the characteristics of a particularly interesting subclass of capsid assembly modulators. These so-called non-HAP CAM-As have intriguing properties in cell culture but also clear virus-infected cells from the mouse liver in a gradual and sustained way. We believe they represent a considerable improvement over previously reported molecules and may one day be part of curative treatment combinations for chronic hepatitis B.