Aberrant cyclin A expression and centrosome overduplication induced by hepatitis B virus pre-S2 mutants and its implication in hepatocarcinogenesis

HBV-related HCC development in mice is STAT3 dependent and indicates an oncogenic effect of HBx

Background & Aims

Although most hepatocellular carcinoma (HCC) cases are driven by hepatitis and cirrhosis, a subset of patients with chronic hepatitis B develop HCC in the absence of advanced liver disease, indicating the oncogenic potential of hepatitis B virus (HBV). We investigated the role of HBV transcripts and proteins on HCC development in the absence of inflammation in HBV-transgenic mice.

Methods

HBV-transgenic mice replicating HBV and expressing all HBV proteins from a single integrated 1.3-fold HBV genome in the presence or absence of wild-type HBx (HBV1.3/HBVxfs) were analyzed. Flow cytometry, molecular, histological and in vitro analyses using human cell lines were performed. Hepatocyte-specific Stat3- and Socs3-knockout was analyzed in HBV1.3 mice.

Results

Approximately 38% of HBV1.3 mice developed liver tumors. Protein expression patterns, histology, and mutational landscape analyses indicated that tumors resembled human HCC. HBV1.3 mice showed no signs of active hepatitis, except STAT3 activation, up to the time point of HCC development. HBV-RNAs covering HBx sequence, 3.5-kb HBV RNA and HBx-protein were detected in HCC tissue. Interestingly, HBVxfs mice expressing all HBV proteins except a C-terminally truncated HBx (without the ability to bind DNA damage binding protein 1) showed reduced signs of DNA damage response and had a significantly reduced HCC incidence. Importantly, intercrossing HBV1.3 mice with a hepatocyte-specific STAT3-knockout abrogated HCC development.

Conclusions

Expression of HBV-proteins is sufficient to cause HCC in the absence of detectable inflammation. This indicates the oncogenic potential of HBV and in particular HBx. In our model, HBV-driven HCC was STAT3 dependent. Our study highlights the immediate oncogenic potential of HBV, challenging the idea of a benign highly replicative phase of HBV infection and indicating the necessity for an HBV 'cure'.

Impact and implications

Although most HCC cases in patients with chronic HBV infection occur after a sequence of liver damage and fibrosis, a subset of patients develops HCC without any signs of advanced liver damage. We demonstrate that the expression of all viral transcripts in HBV-transgenic mice suffices to induce HCC development independent of inflammation and fibrosis. These data indicate the direct oncogenic effects of HBV and emphasize the idea of early antiviral treatment in the 'immune-tolerant' phase (HBeAg-positive chronic HBV infection).

Bibliometric analysis of endoplasmic reticulum stress in hepatocellular carcinoma: trends and future directions

BACKGROUND

Over the past three decades, endoplasmic reticulum (ER) stress has gained considerable attention in the field of hepatocellular carcinoma (HCC) with an increasing number of publications. It is crucial to reveal the global status, research hotspots and future research trends of ER stress in HCC. The aim of this study is to analyze the publications related to ER stress in HCC through bibliometric analysis in order to better understand the current status of ER stress research in HCC and to identify potential new research directions.

METHODS

In this study, articles and reviews on ER stress in HCC up to December 31, 2023 were searched and downloaded from the Science Citation Index-Expanded (SCIE) of the Web of Science Core Collection (WoSCC), Pubmed, Scopus and Embase databases. Using CiteSpace 6.2.R6, VOSviewer 1.6.19, Scimago Graphica and Microsoft Office Excel 2019, the knowledge networks of a variety of countries, regions, authors, references, keywords and journals were analyzed.

RESULTS

A total of 1239 publications were retrieved, including 843 articles and 396 review articles. The number of global publications is increasing every year, with the majority of publications coming from China and the USA. Ih-Jen Su, Wenya Huang and Wei Wei are the top 3 prolific authors. "Progression", "inflammation", "cell cycle arrest", "metabolism", "snsignaling pathways", "pathogenesis" and "non-alcoholic fatty liver disease" have emerged as research hotspots in recent years. The journal with the greatest co-citation is Hepatology.

CONCLUSIONS

Based on current global trends, the total number of publications on ER stress in HCC research will continue to increase, but there is a need for more cooperation between authors and countries/regions. ER stress in HCC will continue to be a research priority.

CONCLUSIONS

Based on current global trends, the total number of publications on ER stress in HCC research will continue to increase, but there is a need for more cooperation between authors and countries/regions. ER stress in HCC will continue to be a research priority.

Overview of hepatocellular carcinoma: from molecular aspects to future therapeutic options

Hepatocellular carcinoma (HCC) is the seventh most highly prevalent malignant tumor globally and the second most common cause of mortality. HCC develops with complex pathways that occur through multistage biological processes. Non-alcoholic fatty liver disease, metabolic-associated fatty liver disease, alcoholic liver disease, autoimmune hepatitis, hepatitis B, and hepatitis C are the causative etiologies of HCC. HCC develops as a result of epigenetic changes, protein-coding gene mutations, and altered signaling pathways. Biomarkers and potential therapeutic targets for HCC open up new possibilities for treating the disease. Immune checkpoint inhibitors are included in the treatment options in combination with molecular targeted therapy.

The role of hepatitis B virus genome variations in HBV-related HCC: effects on host signaling pathways

Hepatocellular carcinoma (HCC) is a significant global health issue, with a high prevalence in many regions. There are variations in the etiology of HCC in different regions, but most cases are due to long-term infection with viral hepatitis. Hepatitis B virus (HBV) is responsible for more than 50% of virus-related HCC, which highlights the importance of HBV in pathogenesis of the disease. The development and progression of HBV-related HCC is a complex multistep process that can involve host, viral, and environmental factors. Several studies have suggested that some HBV genome mutations as well as HBV proteins can dysregulate cell signaling pathways involved in the development of HCC. Furthermore, it seems that the pathogenicity, progression of liver diseases, response to treatment and also viral replication are different among HBV mutants. Understanding the relationship between HBV genome variations and host signaling pathway alteration will improve our understanding of the molecular pathogenesis of HBV-related HCC. Furthermore, investigating commonly dysregulated pathways in HBV-related HCC is necessary to discover more specific therapeutic targets and develop more effective strategies for HCC treatment. The objective of this review is to address the role of HBV in the HCC progression and primarily focus on the impacts of HBV genome variations on HCC-related signaling pathways.

The HBV web: An insight into molecular interactomes between the hepatitis B virus and its host en route to hepatocellular carcinoma

Hepatitis B virus (HBV) is a major aetiology associated with the development and progression of hepatocellular carcinoma (HCC), the most common primary liver malignancy. Over the past few decades, direct and indirect mechanisms have been identified in the pathogenesis of HBV-associated HCC which include altered signaling pathways, genome integration, mutation-induced genomic instability, chromosomal deletions and rearrangements. Intertwining of the HBV counterparts with the host cellular factors, though well established, needs to be systemized to understand the dynamics of host-HBV crosstalk and its consequences on HCC progression. Existence of a vast array of protein-protein and protein-nucleic acid interaction databases has led to the uncoiling of the compendia of genes/gene products associated with these interactions. This review covers the existing knowledge about the HBV-host interplay and brings it down under one canopy emphasizing on the HBV-host interactomics; and thereby highlights new strategies for therapeutic advancements against HBV-induced HCC.

MHBSt167 induced autophagy promote cell proliferation and EMT by activating the immune response in L02 cells

Background

Hepatitis B virus can induce hepatocellular carcinoma (HCC) by inducing a host immune response against infected hepatocytes. C-terminally truncated middle surface protein (MHBSt) has been reported to contribute to HCC through transcriptional activation in epidemiology studies, while the underlying mechanism of MHBSt-induced HCC is unknown.

Methods

In this study, a premature stop at codon 167 in MHBS (MHBSt¹⁶⁷) was investigated into eukaryotic expression plasmid pcDNA3.1(-). MHBSt¹⁶⁷ expressed plasmid was transfected into the L02 cell line, cell proliferation was analyzed by CCK-8 and high-content screening assays, the cell cycle was analyzed by flow cytometry, and epithelial-to-mesenchymal transition and autophagy were analyzed by immunoblotting and immunofluorescence. NF-κB activation and the MHBSt¹⁶⁷-induced immune response were analyzed by immunoblotting and immunofluorescence. IFN-α, IFN-β and IL-1α expression were analyzed by qPCR. Autophagy inhibitors were used to analyze the relationship between the immune response and autophagy.

Results

The results showed that MHBSt¹⁶⁷ promoted L02 cell proliferation, accelerated cell cycle progression from the S to G2 phase and promoted epithelial-to-mesenchymal transition through ER-stress, leading to autophagy and NF-κB activation and increased immune-related factor expression. The MHBSt¹⁶⁷-induced acceleration of cell proliferation and the cell cycle was abolished by autophagy or NF-κB inhibitors.

Conclusion

In summary, MHBSt¹⁶⁷ could promote cell proliferation, accelerate cell cycle progression, induce EMT and activate autophagy through ER-stress to induce the host immune response, supporting a potential role of MHBSt¹⁶⁷ in contributing to carcinogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01840-z.

Association of Increased Programmed Death Ligand 1 Expression and Regulatory T Cells Infiltration with Higher Hepatocellular Carcinoma Recurrence in Patients with Hepatitis B Virus Pre-S2 Mutant after Curative Surgical Resection

Although surgical resection is available as a potentially curative therapy for hepatocellular carcinoma (HCC), high recurrence of HCC after surgery remains a serious obstacle for long-term patient survival. Therefore, the discovery of valuable prognostic biomarkers for HCC recurrence is urgently needed. Pre-S2 mutant is a mutant form of hepatitis B virus (HBV) large surface protein which is expressed from the HBV surface gene harboring deletion mutations spanning the pre-S2 gene segment. Pre-S2 mutant-positive HCC patients have been regarded as a high-risk population of HCC recurrence after resection surgery and display increased immune checkpoint programmed death ligand 1 (PD-L1) expression and pro-tumor regulatory T cells (Tregs) infiltration in tumor tissues. In this study, the association of higher levels of PD-L1 expression and Tregs infiltration in tumor tissues with post-operative HCC recurrence in pre-S2 mutant-positive HCC patients was evaluated. We found that patients with pre-S2 mutant in combination with higher levels of PD-L1 expression and Tregs infiltration in tumor tissues were independently associated with a higher risk of HCC recurrence (hazard ratio, 4.109; p value = 0.0011) and poorer recurrence-free survival (median, 8.2 versus 18.0 months; p value = 0.0004) than those of patients with either one or two of these three biomarkers. Furthermore, a combination of pre-S2 mutant, intra-tumoral PD-L1 expression, and tumor-infiltrating Tregs exhibited superior performance in identifying patients at a higher risk of HCC recurrence (area under the receiver operating characteristic curve, 0.8400). Collectively, this study suggests that higher levels of PD-L1 expression and Tregs infiltration in tumor tissues predicted a higher risk of HCC recurrence in pre-S2 mutant-positive HCC patients after curative surgical resection.

Viral hepatitis and hepatocellular carcinoma: From molecular pathways to the role of clinical surveillance and antiviral treatment

Hepatocellular carcinoma (HCC) is a global health challenge. Due to the high prevalence in low-income countries, hepatitis B virus (HBV) and hepatitis C virus infections remain the main risk factors for HCC occurrence, despite the increasing frequencies of non-viral etiologies. In addition, hepatitis D virus coinfection increases the oncogenic risk in patients with HBV infection. The molecular processes underlying HCC development are complex and various, either independent from liver disease etiology or etiology-related. The reciprocal interlinkage among non-viral and viral risk factors, the damaged cellular microenvironment, the dysregulation of the immune system and the alteration of gut-liver-axis are known to participate in liver cancer induction and progression. Oncogenic mechanisms and pathways change throughout the natural history of viral hepatitis with the worsening of liver fibrosis. The high risk of cancer incidence in chronic viral hepatitis infected patients compared to other liver disease etiologies makes it necessary to implement a proper surveillance, both through clinical-biochemical scores and periodic ultrasound assessment. This review aims to outline viral and microenvironmental factors contributing to HCC occurrence in patients with chronic viral hepatitis and to point out the importance of surveillance programs recommended by international guidelines to promote early diagnosis of HCC.

Surveillance for hepatocellular carcinoma: current status and future perspectives for improvement

INTRODUCTION

Hepatocellular carcinoma (HCC) is a globally relevant medical problem. Fortunately, risk factors for this tumor have been identified, and surveillance protocols developed. Patients with liver cirrhosis have the highest risk of developing HCC and have historically been included in surveillance programs. Special categories have also emerged in recent years, especially patients with eradicated HCV infection or nonalcoholic fatty liver disease. Novel serum biomarkers and magnetic resonance imaging protocols are currently being proposed to refine existing surveillance protocols.

AREAS COVERED

We discuss the rationale of surveillance programs for HCC and report the most recent recommendations from international guidelines about this topic. Gray areas, such as nonalcoholic fatty liver disease and the role of intrahepatic cholangiocellular carcinoma, are also discussed.

EXPERT OPINION

Surveillance is recognized as a tool to favor early diagnosis of HCC, access to curative treatment, and increase survival, even if the supporting evidence is mainly based on observational studies. As new randomized clinical trials are difficult to propose, future challenges will include optimizing implementation in the primary care setting and a more personalized approach, balancing the opportunities and risks of overdiagnosis of novel techniques and biomarkers.

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.

Anti-rheumatic drug-induced hepatitis B virus reactivation and preventive strategies for hepatocellular carcinoma

To date, an estimated 3 million people worldwide have been infected with chronic hepatitis B virus (HBV). Although anti-HBV therapies have improved the long-term survival profile of chronic carriers, viral reactivation still poses a significant challenge for preventing HBV-related hepatitis, hepatocellular carcinoma (HCC), and death. Immuno-modulating drugs, which are widely applied in managing rheumatic conditions, are commonly associated with HBV reactivation (HBVr) as a result of drug-induced immune suppression. However, there are few reports on the risk of HBVr and the medication management plan for HBV carriers, especially rheumatic patients. In this review, we summarize immuno-modulating drug-induced HBVr during rheumatoid therapy and its preventive strategies for HBVr-induced liver diseases, especially cirrhosis and HCC. These findings will assist with developing treatments for rheumatic patients, and prevent HBV-related cirrhosis and HCC.

Nucleotide variants in hepatitis B virus preS region predict the recurrence of hepatocellular carcinoma

Background: Hepatitis B virus (HBV) variants in the preS region have been associated with hepatocellular carcinoma (HCC). However, the effect of the preS variants on HCC prognosis remains largely unknown. We aimed to identify the preS variants that reliably predict postoperative prognosis in HCC.

Methods: RNA-seq data of 203 HCC patients retrieved from public database were screened for the preS variants related to HCC prognosis. The variants in the sera and tumors were then validated in our prospective cohort enrolling 103 HBV-associated HCC patients.

Results: By analyzing prognosis-related gene sets in the RNA-seq data, 12 HBV preS variants were associated with HCC recurrence. Of those, G40C and C147T in the sera predicted an unfavorable recurrence-free survival in our cohort (hazard ratio [HR]=2.18, 95% confidence interval [CI]=1.37-3.47, p=0.001 for G40C; HR=1.84, 95% CI=1.15-2.92, p=0.012 for C147T). G40C and C147T were significantly associated with microscopic vascular invasion, larger tumor size, and abnormal liver function. Multivariate Cox regression analysis showed that G40C significantly increased the risk of HCC recurrence in patients with postoperative antiviral treatment. The HCC prognosis-prediction model consisting of α-fetoprotein and G40C in the sera achieved the best performance (sensitivity=0.80, specificity=0.70, and area under the curve=0.79). Functional analysis indicated that these two variants were associated with cell proliferation, chromosome instability, carcinogenesis, metastasis, and anticancer drug resistance.

Conclusions: G40C and C147T are serological biomarkers for HCC prognosis and the prognostic model consisting of serological α-fetoprotein and G40C achieved the best performance in predicting postoperative prognosis.

Unique Features of Hepatitis B Virus-Related Hepatocellular Carcinoma in Pathogenesis and Clinical Significance

Simple Summary

Hepatitis B virus (HBV) infection is the major risk factor for hepatocellular carcinoma (HCC). Understanding the unique features for HBV-induced HCC can shed new light on the unmet needs in its early diagnosis and effective therapy. During decades of chronic hepatitis B, hepatocytes undergoing repeated damage and regeneration accumulate genetic changes predisposing to HCC development. In addition to traditional mutations in viral and cellular oncogenes, HBV integration into the cell chromosomes is an alternative genetic change contributing to hepatocarcinogenesis. A striking male dominance in HBV-related HCC further highlights an interaction between androgen sex hormone and viral factors, which contributes to the gender difference via stimulating viral replication and activation of oncogenes preferentially in male patients. Meanwhile, a novel circulating tumor biomarker generated by HBV integration shows great potential for the early diagnosis of HCC. These unique HBV-induced hepatocarcinogenic mechanisms provide new insights for the future development of superior diagnosis and treatment strategies.

Abstract

Hepatitis B virus (HBV) infection is one of the important risk factors for hepatocellular carcinoma (HCC) worldwide, accounting for around 50% of cases. Chronic hepatitis B infection generates an inflammatory microenvironment, in which hepatocytes undergoing repeated cycles of damage and regeneration accumulate genetic mutations predisposing them to cancer. A striking male dominance in HBV-related HCC highlights the influence of sex hormones which interact with viral factors to influence carcinogenesis. HBV is also considered an oncogenic virus since its X and surface mutant proteins showed tumorigenic activity in mouse models. The other unique mechanism is the insertional mutagenesis by integration of HBV genome into hepatocyte chromosomes to activate oncogenes. HCC survival largely depends on tumor stages at diagnosis and effective treatment. However, early diagnosis by the conventional protein biomarkers achieves limited success. A new biomarker, the circulating virus–host chimera DNA from HBV integration sites in HCC, provides a liquid biopsy approach for monitoring the tumor load in the majority of HBV–HCC patients. To maximize the efficacy of new immunotherapies or molecular target therapies, it requires better classification of HCC based on the tumor microenvironment and specific carcinogenic pathways. An in-depth study may benefit both the diagnosis and treatment of HBV-related HCC.

Centrosome amplification in cancer and cancer-associated human diseases

Accumulated evidence from genetically modified cell and animal models indicates that centrosome amplification (CA) can initiate tumorigenesis with metastatic potential and enhance cell invasion. Multiple human diseases are associated with CA and carcinogenesis as well as metastasis, including infection with oncogenic viruses, type 2 diabetes, toxicosis by environmental pollution and inflammatory disease. In this review, we summarize (1) the evidence for the roles of CA in tumorigenesis and tumor cell invasion; (2) the association between diseases and carcinogenesis as well as metastasis; (3) the current knowledge of CA in the diseases; and (4) the signaling pathways of CA. We then give our own thinking and discuss perspectives relevant to CA in carcinogenesis and cancer metastasis in human diseases. In conclusion, investigations in this area might not only identify CA as a biological link between these diseases and the development of cancer but also prove the causal role of CA in cancer and progression under pathophysiological conditions, potentially taking cancer research into a new era.

Hepatitis B Virus Pre-S Gene Deletions and Pre-S Deleted Proteins: Clinical and Molecular Implications in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent and fatal human cancers worldwide and its development and prognosis are intimately associated with chronic infection with hepatitis B virus (HBV). The identification of genetic mutations and molecular mechanisms that mediate HBV-induced tumorigenesis therefore holds promise for the development of potential biomarkers and targets for HCC prevention and therapy. The presence of HBV pre-S gene deletions in the blood and the expression of pre-S deleted proteins in the liver tissues of patients with chronic hepatitis B and HBV-related HCC have emerged as valuable biomarkers for higher incidence rates of HCC development and a higher risk of HCC recurrence after curative surgical resection, respectively. Moreover, pre-S deleted proteins are regarded as important oncoproteins that activate multiple signaling pathways to induce DNA damage and promote growth and proliferation in hepatocytes, leading to HCC development. The signaling molecules dysregulated by pre-S deleted proteins have also been validated as potential targets for the prevention of HCC development. In this review, we summarize the clinical and molecular implications of HBV pre-S gene deletions and pre-S deleted proteins in HCC development and recurrence and highlight their potential applications in HCC prevention and therapy.

Tertiary Prevention of HCC in Chronic Hepatitis B or C Infected Patients

Simple Summary

Hepatocellular carcinoma (HCC) recurrence is the major obstacle concerning patients’ survival. Tertiary prevention by antiviral therapies could reduce HCC recurrence rate in both chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infected patients. In chronic hepatitis B (CHB) patients, nucleos(t)ide analogues (Nuc) provide a more effective HCC tertiary prevention effect than an interferon (IFN)-based regimen. In chronic hepatitis C (CHC) patients, the tertiary prevention effect by direct acting antiviral agents (DAAs) was reported non-inferior to that by IFN-based therapy. Chronic hepatitis C patients left untreated had the worst survival benefit as well as shorted recurrence-free interval than those treated by either type of antiviral regimen. Although the risk of HCC recurrence could only be decreased but not diminished by antiviral therapies due to host and microenvironmental factors beyond virus infection, antiviral therapy helps to preserve and improve liver function which makes multi-modality anticancer treatment feasible to improve survival.

Abstract

Hepatocellular carcinoma (HCC) ranks as a leading cause of common cancer and cancer-related death. The major etiology of HCC is due to chronic hepatitis virus including HBV and HCV infections. Scheduled HCC surveillance in high risk populations improves the early detection rate and the feasibility of curative treatment. However, high HCC recurrence rate still accounts for the poor prognosis of HCC patients. In this article, we critically review the pathogenesis of viral hepatitis-related hepatocellular carcinoma and the evidence of tertiary prevention efficacy by current available antiviral treatment, and discuss the knowledge gap in viral hepatitis-related HCC tertiary prevention.

Hyperactivation of cyclin A-CDK induces centrosome overduplication and chromosome tetraploidization in mouse cells

Mammalian cyclin A-CDK (cyclin-dependent kinase) activity during mitotic exit is regulated by two redundant pathways, cyclin degradation and CDK inhibitors (CKIs). Ectopic expression of a destruction box-truncated (thereby stabilized) mutant of cyclin A in the mouse embryonic fibroblasts nullizygous for three CKIs (p21, p27, and p107) results in constitutive activation ("hyperactivation") of cyclin A-CDK and induces rapid tetraploidization, suggesting loss of the two redundant pathways causes genomic instability. To elucidate the mechanism underlying teraploidization by hyperactive cyclin A-CDK, we first examined if the induction of tetraploidization depends on specific cell cycle stage(s). Arresting the cell cycle at either S phase or M phase blocked the induction of tetraploidization, which was restored by subsequent release from the arrest. These results suggest that both S- and M-phase progressions are necessary for the tetraploidization by hyperactive cyclin A-CDK and that the tetraploidization is not caused by chromosome endoreduplication but by mitotic failure. We also observed that the induction of tetraploidization is associated with excessive duplication of centrosomes, which was suppressed by S-phase but not M-phase block, suggesting that hyperactive cyclin A-CDK promotes centrosome overduplication during S phase. Time-lapse microscopy revealed that hyperactive cyclin A-CDK can lead cells to bypass cell division and enter pseudo-G1 state. These observations implicate that hyperactive cyclin A-CDK causes centrosome overduplication, which leads to mitotic slippage and subsequent tetraploidization.

HBV preS deletion mapping using deep sequencing demonstrates a unique association with viral markers

Aim

Deletions are observed frequently in the preS1/S2 region of hepatitis B virus (HBV) genome, in association with liver disease advancement. However, the most significant preS1/S2 region and its influences on viral markers are unclear.

Methods

The preS1/S2 HBV regions of 90 patients without antiviral therapy were subjected to deep sequencing and deleted regions influencing viral markers were investigated.

Results

From the deletion frequency analysis in each patient, deletions were observed most frequently in the preS2 codon 132–141 region. When the patients were divided into three groups (0–0.1%: n = 27, 0.1%-10%: n = 34, 10–100%: n = 29), based on the deletion frequency, FIB-4 (p < 0.01), HBV DNA (p < 0.01), HBcrAg (p < 0.01) and preS1/S2 start codon mutations (p < 0.01, both) were significantly associated with the deletion. When clinical and viral markers were investigated by multivariate analysis for their association with the deletion, FIB-4 (p < 0.05), HBcrAg (p < 0.05), and preS1 start codon mutation (p < 0.01) were extracted as independent variables. When the influence of the preS codon 132-141deletions on HBsAg and HBcrAg, relative to HBV DNA, was investigated, the HBsAg/HBV DNA ratio was lower (0–10% vs. 10%-100%, p<0.05), while the HBcrAg/HBV DNA rati o was higher (0–0.1% vs. 10%-100%, p<0.05) in the presence of the preS codon 132-141deletions.

Conclusion

The preS codon.132-141 deletions have a significant influence on the clinical characteristics and viral markers, even when present as a minor population. Importantly, the preS codon 132–141 deletions have a clear influence on the viral life cycle and pathogenesis.

Hepatitis B Virus Deregulates the Cell Cycle To Promote Viral Replication and a Premalignant Phenotype

Hepatitis B virus (HBV) infection is a major health problem worldwide, and chronically infected individuals are at high risk of developing cirrhosis and hepatocellular carcinoma (HCC). The molecular mechanisms whereby HBV causes HCC are largely unknown. Using a biologically relevant system of HBV infection of primary human hepatocytes (PHHs), we studied how HBV perturbs gene expression and signaling pathways of infected hepatocytes and whether these effects are relevant to productive HBV infection and HBV-associated HCC. Using a human growth factor antibody array, we first showed that HBV infection induced a distinct profile of growth factor production by PHHs, marked particularly by significantly lower levels of the transforming growth factor β (TGF-β) family of proteins in the supernatant. Transcriptome profiling next revealed multiple changes in cell proliferation and cell cycle control pathways in response to HBV infection. A human cell cycle PCR array validated deregulation of more than 20 genes associated with the cell cycle in HBV-infected PHHs. Cell cycle analysis demonstrated that HBV-infected PHHs are enriched in the G₂/M phase compared to the predominantly G₀/G₁ phase of cultured PHHs. HBV proviral host factors, such as PPARA, RXRA, and CEBPB, were upregulated upon HBV infection and particularly enriched in cells in the G₂/M phase. Together, these results support the notion that HBV deregulates cell cycle control to render a cellular environment that is favorable for productive HBV infection. By perturbing cell cycle regulation of infected cells, HBV may coincidently induce a premalignant phenotype that predisposes infected hepatocytes to subsequent malignant transformation.IMPORTANCE Hepatitis B virus (HBV) infection is a major health problem with high risk of developing hepatocellular carcinoma (HCC). By using a biologically relevant system of HBV infection of primary human hepatocytes (PHHs), we studied how HBV perturbs gene expression and whether these effects are relevant to HBV-associated HCC. HBV induced a distinct profile of growth factor production, marked particularly by significantly lower levels of the transforming growth factor β (TGF-β) family of proteins. Transcriptome profiling revealed multiple changes in cell proliferation and cell cycle control pathways. Cell cycle analysis demonstrated that HBV-infected PHHs are enriched in the G₂/M phase. HBV proviral host factors were upregulated upon infection and particularly enriched in cells in the G₂/M phase. Together, these results support the notion that HBV deregulates cell cycle control to render a cellular environment that is favorable for productive infection. This may coincidently induce a premalignant phenotype that predisposes infected hepatocytes to subsequent malignant transformation.

Comprehensive review of Hepatitis B Virus-associated hepatocellular carcinoma research through text mining and big data analytics

PubMed was text mined to glean insights into the role of Hepatitis B virus (HBV) in hepatocellular carcinoma (HCC) from the massive number of publications (9249) available to date. Reports from ∼70 countries identified >1300 human genes associated with either the Core, Surface or X gene in HBV-associated HCC. One hundred and forty-three of these host genes, which can potentially yield 1180 biomolecular interactions, each were reported in at least three different publications to be associated with the same HBV. These 143 genes function in 137 pathways, involved mainly in the cell cycle, apoptosis, inflammation and signalling. Fourteen of these molecules, primarily transcriptional regulators or kinases, play roles in several pathways pertinent to the hallmarks of cancers. 'Chronic' was the most frequent word used across the 9249 abstracts. A key event in chronic HBV infection is the integration of HBV into the host genome. The advent of cost-effective, next-generation sequencing technology facilitated the employment of big-data analytics comprehensively to characterize HBV-host integration within HCC patients. A total of 5331 integration events were reported across seven publications, with most of these integrations observed between the Core/X gene and the introns of genes. Nearly one-quarter of the intergenic integrations are within repeats, especially long interspersed nuclear elements (LINE) repeats. Integrations within 13 genes were each reported by at least three different studies. The human gene with the most HBV integrations observed is the TERT gene where a total of 224 integrations, primarily at its promoter and within the tumour tissue, were reported by six of seven publications. This unique review, which employs state-of-the-art text-mining and data-analytics tools, represents the most complete, systematic and comprehensive review of nearly all the publications associated with HBV-associated HCC research. It provides important resources to either focus future research or develop therapeutic strategies to target key molecules reported to play important roles in key pathways of HCC, through the systematic analyses of the commonly reported molecules associated with the various HBV genes in HCC, including information about the interactions amongst these commonly reported molecules, the pathways in which they reside as well as detailed information regarding the viral and host genes associated with HBV integration in HCC patients. Hence this review, which highlights pathways and key human genes associated with HBV in HCC, may facilitate the deeper elucidation of the role of HBV in hepato-carcinogenesis, potentially leading to timely intervention against this deadly disease.

HuR translocation to the cytoplasm of cancer cells in actin-independent manner

Human antigen R (HuR) is a RNA-binding protein, which binds to the AU-rich element (ARE) in the 3'-untranslated region (3'-UTR) of certain mRNA and is involved in the export and stabilization of ARE-mRNA. HuR constitutively relocates to the cytoplasm in many cancer cells, however the mechanism of intracellular HuR trafficking is poorly understood. To address this question, we examined the functional role of the cytoskeleton in HuR relocalization. We tested the effect of actin depolymerizing macrolide latrunculin A or myosin II ATPase activity inhibitor blebbistatin for HuR relocalization induced by the vasoactive hormone Angiotensin II in cancer and control normal cells. Western blot and confocal imaging data revealed that both inhibitors attenuated the cytoplasmic HuR in normal cells but no such alteration was observed in cancer cells. Concomitant with changes in intracellular HuR localization, both inhibitors markedly decreased the accumulation and half-lives of HuR target ARE-mRNAs in normal cells, whereas no change was observed in cancer cells. Furthermore, co-immunoprecipitation experiments with HuR proteins revealed clear physical interaction with ß-actin only in normal cells. The current study is the first to verify that cancer cells can implicate a microfilament independent HuR transport. We hypothesized that when cytoskeleton structure is impaired, cancer cells can acquire an alternative HuR trafficking strategy.

Hepatitis B virus pre-S/S variants in liver diseases

Chronic hepatitis B is a global health problem. The clinical outcomes of chronic hepatitis B infection include asymptomatic carrier state, chronic hepatitis (CH), liver cirrhosis (LC), and hepatocellular carcinoma (HCC). Because of the spontaneous error rate inherent to viral reverse transcriptase, the hepatitis B virus (HBV) genome evolves during the course of infection under the antiviral pressure of host immunity. The clinical significance of pre-S/S variants has become increasingly recognized in patients with chronic HBV infection. Pre-S/S variants are often identified in hepatitis B carriers with CH, LC, and HCC, which suggests that these naturally occurring pre-S/S variants may contribute to the development of progressive liver damage and hepatocarcinogenesis. This paper reviews the function of the pre-S/S region along with recent findings related to the role of pre-S/S variants in liver diseases. According to the mutation type, five pre-S/S variants have been identified: pre-S deletion, pre-S point mutation, pre-S1 splice variant, C-terminus S point mutation, and pre-S/S nonsense mutation. Their associations with HBV genotype and the possible pathogenesis of pre-S/S variants are discussed. Different pre-S/S variants cause liver diseases through different mechanisms. Most cause the intracellular retention of HBV envelope proteins and induction of endoplasmic reticulum stress, which results in liver diseases. Pre-S/S variants should be routinely determined in HBV carriers to help identify individuals who may be at a high risk of less favorable liver disease progression. Additional investigations are required to explore the molecular mechanisms of the pre-S/S variants involved in the pathogenesis of each stage of liver disease.

Hepatitis B Virus-Associated Hepatocellular Carcinoma

Liver cancer is the fifth most common cancer worldwide in men and the ninth in women. It is also the second most common cause of cancer mortality. Hepatocellular carcinoma (HCC) is the most common type of liver cancer. About 350 million people globally are chronically infected with HBV. Chronic hepatitis B virus (HBV) infection accounts for at least 50% cases of HCC worldwide. Other non-HBV factors may increase HCC risk among persons with chronic HBV infection. Both indirect and direct mechanisms are involved in HCC oncogenesis by HBV. HCC-promoting HBV factors include long-lasting infection, high levels of HBV replication, HBV genotype, HBV integration, specific HBV mutants, and HBV-encoded oncoproteins (e.g., HBx and truncated preS2/S proteins). Recurrent liver inflammation caused by host immune responses during chronic HBV infection can lead to liver fibrosis and cirrhosis and accelerate hepatocyte turnover rate and promote accumulation of mutations. Major breakthroughs have been achieved in the prevention of HBV-associated HCC with HBV vaccines and antiviral therapies.

Pre-S2 Start Codon Mutation of Hepatitis B Virus Subgenotype B3 Effects on NF-κB Expression and Activation in Huh7 Cell Lines

A cross-sectional study on hepatitis B patients in Indonesia showed association of pre-S2 start codon mutation (M120 V) with cirrhosis and hepatocellular carcinoma (HCC), which was dissimilar from studies from other populations where pre-S2 deletion mutation was more prevalent. Different mutation patterns were attributed to different hepatitis B virus (HBV) subgenotypes in each population study. HBV surface proteins are reported to induce the activation of NF-κB, a transcriptional factor known to play an important role in the development of liver disease. This study aimed to see the effects of HBs variants in HBV subgenotype B3 on the expression and activation of NF-κB as one of the mechanisms in inducing advanced liver disease. HBV subgenotypes B3, each carrying wild-type (wt) HBs, M120 V, and pre-S2 deletion mutation were isolated from three HCC patients. HBs genes were amplified and cloned into pcDNA3.1 and were transfected using Lipofectamine into a Huh7 cell line. NF-κB activation was measured through IκB-α expression, which is regulated by NF-κB. RNA expressions for HBs, IκB-α, and NF-κB subunit (p50) were evaluated using real-time PCR. M120 V mutant had a significantly higher mRNA level compared with wt and pre-S2 deletion mutant; however, there were no significant differences in HBs protein expressions. The transcription level of p50 was higher in M120 V mutation compared with HBs wild-type and pre-S2 deletion mutant. NF-κB activation was higher in HBs wild-type compared with the two mutant variants. Pre-S2 mutations had no effect on the increment of NF-κB activation. However, M120 V mutation may utilize a different pathway in liver disease progression that involves high expression of NF-κB subunit, p50.

Hepatitis B virus PreS2-mutant large surface antigen activates store-operated calcium entry and promotes chromosome instability

Hepatitis B virus (HBV) is a driver of hepatocellular carcinoma, and two viral products, X and large surface antigen (LHBS), are viral oncoproteins. During chronic viral infection, immune-escape mutants on the preS2 region of LHBS (preS2-LHBS) are gain-of-function mutations that are linked to preneoplastic ground glass hepatocytes (GGHs) and early disease onset of hepatocellular carcinoma. Here, we show that preS2-LHBS provoked calcium release from the endoplasmic reticulum (ER) and triggered stored-operated calcium entry (SOCE). The activation of SOCE increased ER and plasma membrane (PM) connections, which was linked by ER- resident stromal interaction molecule-1 (STIM1) protein and PM-resident calcium release- activated calcium modulator 1 (Orai1). Persistent activation of SOCE induced centrosome overduplication, aberrant multipolar division, chromosome aneuploidy, anchorage-independent growth, and xenograft tumorigenesis in hepatocytes expressing preS2- LHBS. Chemical inhibitions of SOCE machinery and silencing of STIM1 significantly reduced centrosome numbers, multipolar division, and xenograft tumorigenesis induced by preS2-LHBS. These results provide the first mechanistic link between calcium homeostasis and chromosome instability in hepatocytes carrying preS2-LHBS. Therefore, persistent activation of SOCE represents a novel pathological mechanism in HBV-mediated hepatocarcinogenesis.

Chronic viral hepatitis and its association with liver cancer

Chronic infection with hepatitis viruses represents the major causative factor for end-stage liver diseases, including liver cirrhosis and primary liver cancer (hepatocellular carcinoma, HCC). In this review, we highlight the current understanding of the molecular mechanisms that drive the hepatocarcinogenesis associated with chronic hepatitis virus infections. While chronic inflammation (associated with a persistent, but impaired anti-viral immune response) plays a major role in HCC initiation and progression, hepatitis viruses can also directly drive liver cancer. The mechanisms by which hepatitis viruses induce HCC include: hepatitis B virus DNA integration into the host cell genome; metabolic reprogramming by virus infection; induction of the cellular stress response pathway by viral gene products; and interference with tumour suppressors. Finally, we summarise the limitations of hepatitis virus-associated HCC model systems and the development of new techniques to circumvent these shortcomings.

Pre- and post-operative HBsAg levels may predict recurrence and survival after curative resection in patients with HBV-associated hepatocellular carcinoma

PURPOSE

To investigate pre- and post-operative levels of HBsAg influence prognosis of patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) after curative resection.

METHODS

Medical records were retrospectively analyzed for 881 patients with HBV-related HCC treated by curative resection. Patients were classified as having high or low serum HBsAg levels (≥200 or <200 ng/mL) pre- or post-operatively.

RESULTS

OS and RFS were better for patients with low pre-operative serum levels of HBsAg than for those with high levels. Similarly, OS was better among patients with low post-operative serum levels of HBsAg than among those with high levels. RFS, in contrast, was similar between these two groups. After generating propensity score-matched pairs of patients, OS was higher in patients with falling post-operative HBsAg levels than in those with rising levels. In contrast, RFS was similar between these two groups. Antiviral nucleoside analog therapy prolonged OS in patients with high pre-operative HBsAg levels.

CONCLUSIONS

Low pre- and post-operative levels of HBsAg may be associated with better long-term survival in patients with HBV-related HCC. Pre-operative serum levels of HBsAg ≥200 ng/mL may identify patients more likely to benefit from antiviral treatment.

HBV DNA Integration: Molecular Mechanisms and Clinical Implications

Chronic infection with the Hepatitis B Virus (HBV) is a major cause of liver-related morbidity and mortality. One peculiar observation in cells infected with HBV (or with closely‑related animal hepadnaviruses) is the presence of viral DNA integration in the host cell genome, despite this form being a replicative dead-end for the virus. The frequent finding of somatic integration of viral DNA suggests an evolutionary benefit for the virus; however, the mechanism of integration, its functions, and the clinical implications remain unknown. Here we review the current body of knowledge of HBV DNA integration, with particular focus on the molecular mechanisms and its clinical implications (including the possible consequences of replication-independent antigen expression and its possible role in hepatocellular carcinoma). HBV DNA integration is likely to influence HBV replication, persistence, and pathogenesis, and so deserves greater attention in future studies.

Pre-S2 Mutant-Induced Mammalian Target of Rapamycin Signal Pathways as Potential Therapeutic Targets for Hepatitis B Virus-Associated Hepatocellular Carcinoma

Chronic hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC). Pre-S2 mutant represents an HBV oncoprotein that is accumulated in the endoplasmic reticulum (ER) and manifests as type II ground glass hepatocytes (GGHs). Pre-S2 mutant can induce ER stress and initiate multiple ER stress-dependent or -independent cellular signal pathways, leading to growth advantage of type II GGH. Importantly, the mammalian target of rapamycin (mTOR) signal pathways are consistently activated throughout the liver tumorigenesis in pre-S2 mutant transgenic mice and in human HCC tissues, leading to hepatocyte proliferation, metabolic disorders, and HCC tumorigenesis. In this review, we summarize the pre-S2 mutant-induced mTOR signal pathways and its implications in HBV-related HCC tumorigenesis. Clinically, the presence of pre-S2 mutant exhibits a high resistance to antiviral treatment and carries a high risk of HCC development in patients with chronic HBV infection. Targeting at pre-S2 mutant-induced mTOR signal pathways may thus provide potential strategies for the prevention or therapy of HBV-associated HCC.

Mutations in hepatitis B virus small S genes predict postoperative survival in hepatocellular carcinoma

Hepatitis B virus (HBV) DNA is prone to mutations due to proofreading deficiencies of HBV polymerase. We have previously identified hepatocellular carcinoma (HCC) survival-associated HBV mutations in the X, precore, and core regions. In the present study, we extended our research to assess HCC survival-associated HBV mutations in the small S gene of HBV genome in 115 HCC patients including 60 patients with HBV B genotype, 52 patients with HBV C genotype, and 3 patients with other genotypes. The overfrequencies of mutations at nucleotides 529 and 735 are 8.5% and 91.5%, respectively, but the distribution frequencies of these mutations are not different between HBV genotypes B and C. Mutational sites 529 (relative risk: 3.611, 95% confidence interval [CI]: 1.414-9.221, P=0.007) and 735 (relative risk: 1.905, 95% CI: 1.101-3.297, P=0.021) were identified as statistically significant independent predictors for HCC survival by multivariate survival analysis using a Cox proportional hazards model. Moreover, the mutated 529A and 735T were associated with both short survival time and high HBV DNA load score in HCC patients. The analysis of DNA mutations in the HBV S gene may help identify HCC subgroups with poor prognosis and may provide reference for therapeutic decisions.

Systemic Chromosome Instability Resulted in Colonic Transcriptomic Changes in Metabolic, Proliferation, and Stem Cell Regulators in Sgo1-/+ Mice

Colon cancer is the second most lethal cancer and is predicted to claim 49,700 lives in the United States this year. Chromosome instability (CIN) is observed in 80% to 90% of colon cancers and is thought to contribute to colon cancer progression and recurrence. To investigate the impact of CIN on colon cancer development, we developed shugoshin-1 (Sgo1) haploinsufficient (-/+) mice, an animal model focusing on mitotic error-induced CIN. In this study, we analyzed signature changes in the colonic transcriptome of Sgo1(-/+) mice to examine the molecular events underlying the altered carcinogenesis profiles in Sgo1(-/+) mice. We performed next-generation sequencing of normal-looking colonic mucosal tissue from mice treated with the carcinogen azoxymethane after 24 weeks. Transcriptome profiling revealed 349 hits with a 2-fold expression difference threshold (217 upregulated genes, 132 downregulated genes, P < 0.05). Pathway analyses indicated that the Sgo1-CIN tissues upregulated pathways known to be activated in colon cancer, including lipid metabolism (z score 4.47), Notch signaling (4.47), insulin signaling (3.81), and PPAR pathways (3.75), and downregulated pathways involved in immune responses including allograft rejection (6.69) and graft-versus-host disease (6.54). Notably, stem cell markers were also misregulated. Collectively, our findings demonstrate that systemic CIN results in transcriptomic changes in metabolism, proliferation, cell fate, and immune responses in the colon, which may foster a microenvironment amenable to cancer development. Therefore, therapeutic approaches focusing on these identified pathways may be valuable for colon cancer prevention and treatment.

Mechanisms of HBV-induced hepatocellular carcinoma

Hepatitis B virus (HBV) contributes to hepatocellular carcinoma (HCC) development through direct and indirect mechanisms. HBV DNA integration into the host genome occurs at early steps of clonal tumor expansion and induces both genomic instability and direct insertional mutagenesis of diverse cancer-related genes. Prolonged expression of the viral regulatory protein HBx and/or altered versions of the preS/S envelope proteins dysregulates cell transcription and proliferation control and sensitizes liver cells to carcinogenic factors. Accumulation of preS1 large envelope proteins and/or preS2/S mutant proteins activates the unfold proteins response, that can contribute to hepatocyte transformation. Epigenetic changes targeting the expression of tumor suppressor genes occur early in the development of HCC. A major role is played by the HBV protein, HBx, which is recruited on cellular chromatin and modulates chromatin dynamics at specific gene loci. Compared with tumors associated with other risk factors, HBV-related tumors have a higher rate of chromosomal alterations, p53 inactivation by mutations and overexpression of fetal liver/hepatic progenitor cells genes. The WNT/β-catenin pathway is also often activated but HBV-related tumors display a low rate of activating β-catenin mutations. HBV-related HCCs may arise on non-cirrhotic livers, further supporting the notion that HBV plays a direct role in liver transformation by triggering both common and etiology specific oncogenic pathways in addition to stimulating the host immune response and driving liver chronic necro-inflammation.

Hepatocellular carcinoma and hepatitis B surface protein

The tumorigenesis of hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) has been widely studied. HBV envelope proteins are important for the structure and life cycle of HBV, and these proteins are useful for judging the natural disease course and guiding treatment. Truncated and mutated preS/S are produced by integrated viral sequences that are defective for replication. The preS/S mutants are considered “precursor lesions” of HCC. Different preS/S mutants induce various mechanisms of tumorigenesis, such as transactivation of transcription factors and an immune inflammatory response, thereby contributing to HCC. The preS2 mutants and type II “Ground Glass” hepatocytes represent novel biomarkers of HBV-associated HCC. The preS mutants may induce the unfolded protein response and endoplasmic reticulum stress-dependent and stress-independent pathways. Treatments to inhibit hepatitis B surface antigen (HBsAg) and damage secondary to HBsAg or the preS/S mutants include antivirals and antioxidants, such as silymarin, resveratrol, and glycyrrhizin acid. Methods for the prevention and treatment of HCC should be comprehensive.

Significance of hepatitis virus infection in the oncogenic initiation of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Chronic infection of hepatitis B virus (HBV) and/or hepatitis C virus (HCV) is a major risk factor in the development of the HCC, independently from excessive alcohol abuse and metabolic disease. Since the biology of HBV and HCV is different, their oncogenic effect may go through different mechanisms, direct and/or indirect. Viral hepatitis infection is associated with cellular inflammation, oxidative stress, and DNA damage, that may lead to subsequent hepatic injuries such as chronic hepatitis, fibrosis, cirrhosis, and finally HCC. Direct oncogenic properties of these viruses are related with their genotypic characteristics and the ability of viral proteins to interact with host proteins, thus altering the molecular pathways balance of the cells. In addition, the integration of HBV DNA, especially the gene S and X, in a particular site of the host genome can disrupt chromosomal stability and may activate various oncogenic mechanisms, including those in hematopoietic cells. Recently, several studies also had demonstrated that viral hepatitis could trigger the population of hepatic cancer stem cells. This review summarize available pre-clinical and clinical data in literature regarding oncogenic properties of HBV and HCV in the early initiation of HCC.

Genetic variation of hepatitis B virus and its significance for pathogenesis

Hepatitis B virus (HBV) has a worldwide distribution and is endemic in many populations. Due to its unique life cycle which requires an error-prone reverse transcriptase for replication, it constantly evolves, resulting in tremendous genetic variation in the form of genotypes, sub-genotypes, and mutations. In recent years, there has been considerable research on the relationship between HBV genetic variation and HBV-related pathogenesis, which has profound implications in the natural history of HBV infection, viral detection, immune prevention, drug treatment and prognosis. In this review, we attempted to provide a brief account of the influence of HBV genotype on the pathogenesis of HBV infection and summarize our current knowledge on the effects of HBV mutations in different regions on HBV-associated pathogenesis, with an emphasis on mutations in the preS/S proteins in immune evasion, occult HBV infection and hepatocellular carcinoma (HCC), mutations in polymerase in relation to drug resistance, mutations in HBV core and e antigen in immune evasion, chronicalization of infection and hepatitis B-related acute-on-chronic liver failure, and finally mutations in HBV x proteins in HCC.

CUL4A facilitates hepatocarcinogenesis by promoting cell cycle progression and epithelial-mesenchymal transition

CUL4A, a member of the CULLIN family, functions as a scaffold protein for an E3 ubiquitin ligase. It was reported that the CUL4A gene showed amplification in some human primary hepatocellular carcinomas (HCC). However, the exact role of CUL4A in HCC remains unknown. Here, we aimed to investigate the expression and function of CUL4A in HCC development. Through immunohistochemistry study, we showed increased CUL4A expression in HCC tissues. Statistical analysis disclosed an inverse correlation between CUL4A expression and tumor differentiation grade, and patient survival, but a positive correlation with hepatocyte proliferation as well as lymphatic and venous invasion. CUL4A expression in HCC tissues was associated with HBeAg status in patients and upregulated by HBV in HCC cell lines. Further functional assay showed that CUL4A overexpression significantly promoted growth of H22 tumor homografts in BALB/c mice. Consistently, CUL4A knockdown inhibited the proliferation of established HCC cells, accompanied by S-phase reduction and Cyclin A and Cyclin B1 repression. Furthermore, CUL4A siRNA ameliorated the motility of HCC cell lines with altered expression of epithelial-mesenchymal transition (EMT)-associated molecules. Taken together, our findings indicate that CUL4A plays a pivotal role in HCC progression and may serve as a potential marker for clinical diagnosis and target for therapy.

USP14 activation promotes tumor progression in hepatocellular carcinoma

To elucidate the molecular mechanisms underlying the pathogenesis and treatment of human primary hepatocellular carcinoma (HCC), it is important to explore novel HCC-associated genes. In the present study, we examined the expression of ubiquitin-specific peptidase 14 (USP14) in patients with HCC using quantitative PCR and immunohistochemical techniques. The expression of USP14 in tumor tissues of patients with HCC was significantly higher than that in adjacent non-cancerous and normal liver tissues. It was also determined whether the expression profile of USP14 was associated with the clinical characteristics of HCC. Increased USP14 expression was associated with some clinicopatho-logical variables, such as advancing tumor stage. A Kaplan-Meier curve analysis demonstrated that patients with HCC having a high USP14 expression had a significantly poorer prognosis after surgery than patients with lower USP14 expression levels. Knockdown of USP14 with the lentiviral vector delivery of shRNA in human hepatocarcinoma SMMC7721 cells suppressed cell proliferation, altered the cell cycle and induced cell apoptosis. Additionally, the Wnt/β-catenin pathway was activated in HCC patients with USP14 overexpression. These findings strongly suggested that USP14 activation plays an oncogenic role in promoting tumor progression in HCC. Thus, our findings suggested that USP14 is involved in the progression of HCC and may be a useful therapeutic target in HCC. These findings likely reflect the key role that USP14 plays in the pathogenesis of HCC. Therefore, the identification of USP14 and USP14-driven genes may promote the investigation of its functional role to develop more effective therapies for HCC, especially advanced HCC.

Clonal expansion of hepatocytes with a selective advantage occurs during all stages of chronic hepatitis B virus infection

Hepatocyte clone size was measured in liver samples of 21 patients in various stages of chronic hepatitis B virus (HBV) infection and from 21 to 76 years of age. Hepatocyte clones containing unique virus-cell DNA junctions formed by the integration of HBV DNA were detected using inverse nested PCR. The maximum hepatocyte clone size tended to increase with age, although there was considerable patient-to-patient variation in each age group. There was an upward trend in maximum clone size with increasing fibrosis, inflammatory activity and with seroconversion from HBV e-antigen (HBeAg)-positive to HBeAg-negative, but these differences did not reach statistical significance. Maximum hepatocyte clone size did not differ between patients with and without a coexisting hepatocellular carcinoma. Thus, large hepatocyte clones containing integrated HBV DNA were detected during all stages of chronic HBV infection. Using laser microdissection, no significant difference in clone size was observed between foci of HBV surface antigen (HBsAg)-positive and HBsAg-negative hepatocytes, suggesting that expression of HBsAg is not a significant factor in clonal expansion. Laser microdissection also revealed that hepatocytes with normal-appearing histology make up a major fraction of the cells undergoing clonal expansion. Thus, preneoplasia does not appear to be a factor in the clonal expansion detected in our assays. Computer simulations suggest that the large hepatocyte clones are not produced by random hepatocyte turnover but have an as-yet-unknown selective advantage that drives increased clonal expansion in the HBV-infected liver.

Hepatitis B virus pre-S2 mutant large surface protein inhibits DNA double-strand break repair and leads to genome instability in hepatocarcinogenesis

Although hepatitis B virus (HBV) has been established to cause hepatocellular carcinoma (HCC), the exact mechanism remains to be clarified. Type II ground glass hepatocytes (GGHs) harbouring the HBV pre-S2 mutant large surface protein (LHBS) have been recognized as a morphologically distinct hallmark of HCC in the advanced stages of chronic HBV infection. Considering its preneoplastic nature, we hypothesized that type II GGH may exhibit high genomic instability, which is important for the carcinogenic process in chronic HBV carriers. In this study we found that pre-S2 mutant LHBS directly interacted with importin α1, the key factor that recognizes cargos undergoing nuclear transportation mediated by the importin α/β-associated nuclear pore complex (NPC). By interacting with importin α1, which inhibits its function as an NPC factor, pre-S2 mutant LHBS blocked nuclear transport of an essential DNA repair and recombination factor, Nijmegen breakage syndrome 1 (NBS1), upon DNA damage, thereby delaying the formation of nuclear foci at the sites of DNA double-strand breaks (DSBs). Pre-S2 mutant LHBS was also found to block NBS1-mediated homologous recombination repair and induce multi-nucleation of cells. In addition, pre-S2 mutant LHBS transgenic mice showed genomic instability, indicated by increased global gene copy number variations (CNVs), which were significantly higher than those in hepatitis B virus X mice, indicating that pre-S2 mutant LHBS is the major viral oncoprotein inducing genomic instability in HBV-infected hepatocytes. Consistently, the human type II GGHs in HCC patients exhibited increased DNA DSBs representing significant genomic instability. In conclusion, type II GGHs harbouring HBV pre-S2 mutant oncoprotein represent a high-risk marker for the loss of genome integrity in chronic HBV carriers and explain the complex chromosome changes in HCCs. Mouse array CGH raw data: GEO Accession No. GSE61378 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE61378).

Tumor-promoting/progressing role of additional chromosome instability in hepatic carcinogenesis in Sgo1 (Shugoshin 1) haploinsufficient mice

A major etiological risk factor for hepatocellular carcinoma (HCC) is infection by Hepatitis viruses, especially hepatitis B virus and hepatitis C virus. Hepatitis B virus and hepatitis C virus do not cause aggressive activation of an oncogenic pathway, but they transactivate a broad array of genes, cause chronic inflammation, and, through interference with mitotic processes, lead to mitotic error-induced chromosome instability (ME-CIN). However, how ME-CIN is involved in the development of HCC remains unclear. Delineating the effect of ME-CIN on HCC development should help in identifying measures to combat HCC. In this study, we used ME-CIN model mice haploinsufficient in Shugoshin 1 (Sgo1(-/+)) to assess the role of ME-CIN in HCC development. Treatment with the carcinogen azoxymethane caused Sgo1(-/+) ME-CIN model mice to develop HCCs within 6 months, whereas control mice developed no HCC (P < 0.003). The HCC development was associated with expression of early HCC markers (glutamine synthetase, glypican 3, heat shock protein 70, and the serum marker alpha fetoprotein), although without fibrosis. ME-CIN preceded the expression of HCC markers, suggesting that ME-CIN is an important early event in HCC development. In 12-month-old untreated Sgo1 mice, persistent DNA damage, altered gene expression, and spontaneous HCCs were observed. Sgo1 protein accumulated in response to DNA damage in vitro. Overall, Sgo1(-/+)-mediated ME-CIN strongly promoted/progressed development of HCC in the presence of an initiator carcinogen, and it had a mild initiator effect by itself. Use of the ME-CIN model mice should help in identifying drugs to counteract the effects of ME-CIN and should accelerate anti-HCC drug development.

Inactivation of p53 in Human Keratinocytes Leads to Squamous Differentiation and Shedding via Replication Stress and Mitotic Slippage

Tumor suppressor p53 is a major cellular guardian of genome integrity, and its inactivation is the most frequent genetic alteration in cancer, rising up to 80% in squamous cell carcinoma (SCC). By adapting the small hairpin RNA (shRNA) technology, we inactivated endogenous p53 in primary epithelial cells from the epidermis of human skin. We show that either loss of endogenous p53 or overexpression of a temperature-sensitive dominant-negative conformation triggers a self-protective differentiation response, resulting in cell stratification and expulsion. These effects follow DNA damage and exit from mitosis without cell division. p53 preserves the proliferative potential of the stem cell compartment and limits the power of proto-oncogene MYC to drive cell cycle stress and differentiation. The results provide insight into the role of p53 in self-renewal homeostasis and help explain why p53 mutations do not initiate skin cancer but increase the likelihood that cancer cells will appear.

The emerging role of hepatitis B virus pre-S2 deletion mutant proteins in HBV tumorigenesis

Chronic hepatitis B virus (HBV) infection can cause hepatocellular carcinoma (HCC). Several hypotheses have been proposed to explain the mechanisms of HBV tumorigenesis, including inflammation and liver regeneration associated with cytotoxic immune injuries and transcriptional activators of mutant HBV gene products. The mutant viral oncoprotein-driven tumorigenesis is prevailed at the advanced stage or anti-HBe-positive phase of chronic HBV infection. Besides HBx, the pre-S2 (deletion) mutant protein represents a newly recognized oncoprotein that is accumulated in the endoplasmic reticulum (ER) and manifests as type II ground glass hepatocytes (GGH). The retention of pre-S2 mutant protein in ER can induce ER stress and initiate an ER stress-dependent VEGF/Akt/mTOR and NFκB/COX-2 signal pathway. Additionally, the pre-S2 mutant large surface protein can induce an ER stress-independent pathway to transactivate JAB-1/p27/RB/cyclin A,D pathway, leading to growth advantage of type II GGH. The pre-S2 mutant protein-induced ER stress can also cause DNA damage, centrosome overduplication, and genomic instability. In 5-10% of type II GGHs, there is co-expression of pre-S2 mutant protein and HBx antigen which exhibited enhanced oncogenic effects in transgenic mice. The mTOR signal cascade is consistently activated throughout the course of pre-S2 mutant transgenic livers and in human HCC tissues, leading to metabolic disorders and HCC tumorigenesis. Clinically, the presence of pre-S2 deletion mutants in sera frequently develop resistance to nucleoside analogues anti-virals and predict HCC development. The pre-S2 deletion mutants and type II GGHs therefore represent novel biomarkers of HBV-related HCCs. A versatile DNA array chip has been developed to detect pre-S2 mutants in serum. Overall, the presence of pre-S2 mutants in serum has implications for anti-viral treatment and can predict HCC development. Targeting at pre-S2 mutant protein-induced, ER stress-dependent, mTOR signal cascade and metabolic disorders may offer potential strategy for chemoprevention or therapy in high risk chronic HBV carriers.

The cytoskeletal inhibitors latrunculin A and blebbistatin exert antitumorigenic properties in human hepatocellular carcinoma cells by interfering with intracellular HuR trafficking

The impact of the RNA-binding protein HuR for the post-transcriptional deregulation of tumor-relevant genes is well established. Despite of elevations in HuR expression levels, an increase in cytoplasmic HuR abundance in many cases correlates with a high grade of malignancy. Here, we demonstrated that administration of the actin-depolymerizing macrolide latrunculin A, or blebbistatin, an inhibitor of myosin II ATPase activity, caused a dose- and time-dependent reduction in the high cytoplasmic HuR content of HepG2 and Huh7 hepatocellular carcinoma (HCC) cells. Subcellular fractionation revealed that in addition, both inhibitors strongly attenuated cytoskeletal and membrane-bound HuR abundance and conversely increased the HuR amount in nuclear cell fractions. Concomitant with changes in intracellular HuR localization, both cytoskeletal inhibitors markedly decreased the half-lives of cyclooxygenase-2 (COX-2), cyclin A and cyclin D1 encoding mRNAs resulting in a significant reduction in their expression levels in HepG2 cells. Importantly, a similar reduction in the expression of these HuR targets was achieved by a RNA interference (RNAi)-mediated knockdown of either HuR or nonmuscle myoin IIA. Using polysomal fractionation, we further demonstrate that the decrease in cytoplasmic HuR by latrunculin A or blebbistatin is accompanied by a marked change in the allocation of HuR and its mRNA cargo from polysomes to ribonucleoprotein (RNP) particles. Functionally, the basal migration and prostaglandin E2 synthesis are similarly impaired in inhibitor-treated and stable HuR-knockdown HepG2 cells. Our data demonstrate that interfering with the actomyosin-dependent HuR trafficking may comprise a valid therapeutic option for antagonizing pathologic posttranscriptional gene expression by HuR and furthermore emphasize the potential benefit of HuR inhibitory strategies for treatment of HCC.

Modulation of the unfolded protein response by the human hepatitis B virus

During productive viral infection the host cell is confronted with synthesis of a vast amount of viral proteins which must be folded, quality controlled, assembled and secreted, perturbing the normal function of the endoplasmic reticulum (ER). To counteract the ER stress, cells activate specific signaling pathways, designated as the unfolded proteins response (UPR), which essentially increase their folding capacity, arrest protein translation, and degrade the excess of misfolded proteins. This cellular defense mechanism may, in turn, affect significantly the virus life-cycle. This review highlights the current understanding of the mechanisms of the ER stress activation by Human Hepatitis B virus (HBV), a deadly pathogen affecting more than 350 million people worldwide. Further discussion addresses the latest discoveries regarding the adaptive strategies developed by HBV to manipulate the UPR for its own benefits, the controversies in the field and future perspectives.