The preS2/S region of integrated hepatitis B virus DNA encodes a transcriptional transactivator

CA10 is associated with HBV-related hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the main threat for the patients infected with hepatitis B virus (HBV), but the oncogenic mechanism of HBV-related HCC is still controversial. Previously, we have found that several HBV surface gene (HBS) non-sense mutations are oncogenic. Among these mutations, sW182* was found to have the most potent oncogenicity. In this study, we found that Carbonic Anhydrase X (CA10) level was specifically increased in sW182* mutant-expressing cells. CA10 overexpression was also associated with HBS nonsense mutation in HBV-related HCC tumor tissues. Transformation and tumorigenesis assays revealed that CA10 had significant oncogenic activity. In addition, CA10 overexpression resulted in dysregulation of apoptosis-related proteins, including Mcl-1, Bcl-2, Bcl-xL and Bad. While searching for the regulatory mechanism of CA10, miR-27b was found to downregulate CA10 expression by regulating its mRNA degradation and its expression was decreased in sW182* mutant cells. Moreover, CA10 overexpression was associated with down-regulation of miR-27b in human HBV-related HCC tumor tissues with sW182* mutation. Therefore, induction of the expression of CA10 through repression of miR-27b by sW182* might be one mechanism involved in HBS mutation-related hepatocarcinogenesis.

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CA10 was specifically increased in cells expressing HBV surface gene (HBS) with W182 non-sense mutation.

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CA10 induced cell proliferation, migration and invasion that significantly promoted tumorigenesis in the xenograft study.

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CA10 overexpression could result in dysregulation of apoptosis-related proteins, including Mcl-1, Bcl-2, Bcl-X_L and Bad.

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MicroRNA-27b could downregulate CA10 expression by regulating its mRNA degradation.

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CA10 overexpression was associated with down-regulation of miR-27b in sW182* mutant cell and HBV-related HCC tumor tissues.

Pathogenicity and virulence of Hepatitis B virus

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

[Hepatitis B and C: mechanisms of virus-induced liver pathogenesis and tumorigenesis]

Worldwide, the hepatitis B and hepatitis C viruses (HBV, HCV) are the most relevant causative viral agents of a chronic hepatitis (inflammation of the liver). At present, more than 250 million people suffer from a chronic HBV infection globally, resulting in 0.8 million deaths per year. A chronic HCV infection accounts for about 70 million cases worldwide, leading to a death toll of about 1 million per year. An approved vaccine is only available against an HBV infection. Both HBV and HCV infections result in a highly increased risk of developing liver fibrosis, cirrhosis, and a hepatocellular carcinoma (HCC).This review aims to describe mechanisms of the HBV- and HCV-associated pathogenesis. The focus is on the interplay between a chronic infection with intracellular signaling transduction, metabolic pathways with an emphasis on lipid metabolism, the establishment of liver fibrosis and cirrhosis during a chronic infection, and the mechanisms of the onset of a virally induced HCC.Despite there being great advances in the characterization of viral life cycles and the development of robust antiviral strategies, significant hurdles persist: gaining a better understanding of the mechanisms that drive virus-associated pathogenesis as well as increasing insights regarding different viral genotypes having impacts on alternate pathogeneses.

Long-read sequencing reveals the structural complexity of genomic integration of HBV DNA in hepatocellular carcinoma

The integration of HBV DNA into the human genome can disrupt its structure in hepatocellular carcinoma (HCC), but the complexity of HBV genomic integration remains elusive. Here we applied long-read sequencing to precisely elucidate the HBV integration pattern in the human hepatocellular genome. The DNA library was sequenced using the long-read sequencing on GridION and PacBio Sequel II, respectively. The DNA and mRNA were sequenced using next-generation sequencing on Illumina NextSeq. BLAST (Basic Local Alignment Search Tool) and local scripts were used to analyze HBV integration patterns. We established an analytical strategy based on the long-read sequences, and analyzed the complexity of HBV DNA integration into the hepatocellular genome. A total of 88 integrated breakpoints were identified. HBV DNA integration into human genomic DNA was mainly fragmented with different orientations, rarely with a complete genome. The same HBV integration breakpoints were identified among the three platforms. Most breakpoints were observed at P, X, and S genes in the HBV genome, and observed at introns, intergenic sequences, and exons in the human genome. Tumor tissue harbored a much higher integrated number than the adjacent tissue, and the distribution of HBV integrated into human chromosomes was more concentrated. HBV integration shows different patterns between cancer cells and adjacent normal cells. We for the first time obtained the entire HBV integration pattern through long-read sequencing and demonstrated the value of long-read sequencing in detecting the genomic integration structures of viruses in host cells.

Targeted Long-Read Sequencing Reveals Comprehensive Architecture, Burden and Transcriptional Signatures from HBV-Associated Integrations and Translocations in HCC Cell Lines

Hepatitis B virus (HBV) can integrate into the chromosomes of infected hepatocytes, creating potentially oncogenic lesions that can lead to hepatocellular carcinoma (HCC). However, our current understanding of integrated HBV DNA architecture, burden and transcriptional activity is incomplete due to technical limitations. A combination of genomics approaches was used to describe HBV integrations and corresponding transcriptional signatures in three HCC cell lines: huH-1, PLC/PRF/5 and Hep3B. To generate high coverage long-read sequencing data, a custom panel of HBV-targeting biotinylated oligonucleotide probes was designed. Targeted long-read DNA sequencing captured entire HBV integration events within individual reads, revealing that integrations may include deletions and inversions of viral sequences. Surprisingly, all three HCC cell lines contain integrations that are associated with host chromosomal translocations. In addition, targeted long-read RNA sequencing allowed for the assignment of transcriptional activity to specific integrations and resolved the contribution of overlapping HBV transcripts. HBV transcripts chimeric with host sequences were resolved in their entirety and often included >1000bp of host sequence. This study provides the first comprehensive description of HBV integrations and associated transcriptional activity in three commonly utilized HCC-derived cell lines. The application of novel methods sheds new light on the complexity of these integrations, including HBV bidirectional transcription, nested transcripts, silent integrations and host genomic rearrangements. The observation of multiple HBV-associated chromosomal translocations gives rise to the hypothesis that HBV may be a driver of genetic instability and provides a potential new mechanism for HCC development. Importance HCC-derived cell lines have served as practical models to study HBV biology for decades. These cell lines harbor multiple HBV integrations and express only HBV surface antigen (HBsAg). To date, an accurate description of the integration burden, architecture and transcriptional profile of these cell lines has been limited due to technical constraints. We have developed a targeted long-read sequencing assay which reveals the entire architecture of integrations in these cell lines. In addition, we identified five chromosomal translocations with integrated HBV DNA at the inter-chromosomal junctions. Incorporation of long-read RNA-Seq data indicated that many integrations and translocations were transcriptionally silent. The observation of multiple HBV-associated translocations has strong implications regarding the potential mechanisms for the development of HBV-associated HCC.

HBV Integration Induces Complex Interactions between Host and Viral Genomic Functions at the Insertion Site

Hepatitis B virus (HBV), one of the well-known DNA oncogenic viruses, is the leading cause of hepatocellular carcinoma (HCC). In infected hepatocytes, HBV DNA can be integrated into the host genome through an insertional mutagenesis process inducing tumorigenesis. Dissection of the genomic features surrounding integration sites will deepen our understanding of mechanisms underlying integration. Moreover, the quantity and biological activity of integration sites may reflect the DNA damage within affected cells or the potential survival benefits they may confer. The well-known human genomic features include repeat elements, particular regions (such as telomeres), and frequently interrupted genes (e.g., telomerase reverse transcriptase [i.e. TERT], lysine methyltransferase 2B [i.e. KMT2B], cyclin E1 [CCNE1], and cyclin A2 [CCNA2]). Consequently, distinct genomic features within diverse integrations differentiate their biological functions. Meanwhile, accumulating evidence has shown that viral proteins produced by integrants may cause cell damage even after the suppression of HBV replication. The integration-derived gene products can also serve as tumor markers, promoting the development of novel therapeutic strategies for HCC. Viral integrants can be single copy or multiple copies of different fragments with complicated rearrangement, which warrants elucidation of the whole viral integrant arrangement in future studies. All of these considerations underlie an urgent need to develop novel methodology and technology for sequence characterization and function evaluation of integration events in chronic hepatitis B-associated disease progression by monitoring both host genomic features and viral integrants. This endeavor may also serve as a promising solution for evaluating the risk of tumorigenesis and as a companion diagnostic for designing therapeutic strategies targeting integration-related disease complications.

Mapping RNA

Details of the fine structure of a particular transcript may be assessed by S1 mapping or ribonuclease protection. The use of either of these techniques allows the detection of the 5' and 3' ends of a particular mRNA, as well as the splice junctions, precursors, and processing intermediates of mRNA. Primer extension provides a measure of the amount of a particular mRNA species and allows an exact determination of the 5' end of the mRNA. These three methods are introduced here.

Surveillance Strategy for Patients With BCLC Stage B Hepatocellular Carcinoma After Achieving Complete Remission: Data From the Real World

Purpose: There is a lack of consensus on the surveillance strategy for Barcelona Clinic liver cancer (BCLC) stage B hepatocellular carcinoma (HCC) patients with complete remission (CR). We performed a real-world, retrospective analysis of the surveillance strategy for BCLC stage B HCC patients after radical therapy with CR to support clinical decision-making.

Materials and Methods: We analyzed 546 BCLC stage B HCC patients with CR after radical treatments (surgery/ablation) at Sun Yat-sen University Cancer Center, from January 2007 to December 2019. The intensity of surveillance interval was defined as the mean of surveillance interval within 2 years. The primary endpoint of the study was overall survival (OS) and extra-Milan criteria relapse.

Results: During a median follow-up time of 23.9 months (range = 3.1–148.3 months), there were 11.9% of patients died, 56.6% of patients developed recurrence, the vast majority of patients experienced recurrence within 2 years, and 27.8% patients developed extra-Milan criteria recurrence. The median disease-free survival and OS were 33.6 and 60.0 months, respectively. Patients were divided into regular surveillance group (RS) (≤4.3 months) and irregular surveillance (IRS) group (>4.3 months) based on the optimal cutoff value of the intensity of surveillance interval. The RS group owned a lower incident of extra-Milan criteria relapse and smaller and fewer tumors at recurrence than IRS group, which contributed to the prolonged OS. Besides, the cutoff values of surveillance interval that could lead to significant differences in the incidence of extra-Milan criteria relapse during 0–6, 6–12, and 12–18 months after CR were 2.6, 2.9, and 3 months, respectively.

Conclusions: The average surveillance interval for patients with BCLC stage B HCC achieved CR should not exceed 4.3 months during the first 2 years' follow-up. During three different phases of the initial 18 months after CR, individualized surveillance showed intervals no more than 3 months were required to reduce the incidence of extra-Milan criteria relapse.

TIMM29 interacts with hepatitis B virus preS1 to modulate the HBV life cycle

Hepatitis B virus (HBV), a major global health problem, can cause chronic hepatitis, liver cirrhosis, and hepatocellular carcinomas in chronically infected patients. However, before HBV infection can be adequately controlled, many mysteries about the HBV life cycle must be solved. In this study, TIMM29, an inner mitochondrial membrane protein, was identified as an interaction partner of the preS1 region of the HBV large S protein. The interaction was verified by both an immunoprecipitation with preS1 peptides and a GST-pulldown assay. Immunofluorescence studies also showed colocalization of preS1 and TIMM29. Moreover, it was determined that the preS1 bound with amino acids 92-189 of the TIMM29 protein. Infection of HBV in TIMM29-overexpressing NTCP/G2 cells resulted in a significant decrease of HBeAg and both extracellular particle-associated and core particle-associated HBV DNA without affecting cccDNA formation. Comparable results were obtained with TIMM29-overexpressing HB611 cells, which constitutively produce HBV. In contrast, knockout of TIMM29 in NTCP/G2 cells led to a higher production of HBV including HBeAg expression, as did knockout of TIMM29 in HB611. Collectively, these results suggested that TIMM29 interacts with the preS1 region of the HBV large S protein and modulates HBV amplification.

Hepatitis B Virus preS/S Truncation Mutant rtM204I/sW196* Increases Carcinogenesis through Deregulated HIF1A, MGST2, and TGFbi

Inevitable long-term therapy with nucleos(t)ide analogs in patients with chronic hepatitis B virus (HBV) infection has selected reverse-transcriptase (rt) mutants in a substantial proportion of patients. Some of these mutants introduce premature stop codons in the overlapping surface (s) gene, including rtA181T/sW172*, which has been shown to enhance oncogenicity. The oncogenicity of another drug-resistant mutant, rtM204I/sW196*, has not been studied. We constructed plasmids harboring rtM204I/sW196* and assessed the in vitro cell transformation, endoplasmic reticulum (ER) stress response, and xenograft tumorigenesis of the transformants. Cellular gene expression was analyzed by cDNA microarray and was validated. The rtM204I/sW196* transformants, compared with the control or wild type, showed enhanced transactivation activities for c-fos, increased cell proliferation, decreased apoptosis, more anchorage-independent growth, and enhanced tumor growth in mouse xenografts. X box-binding protein-1 (XBP1) splicing analysis showed no ER stress response. Altered gene expressions, including up-regulated MGST2 and HIF1A, and downregulated transforming growth factor beta-induced (TGFbi), were unveiled by cDNA microarray and validated by RT-qPCR. The TGFbi alteration occurred in transformants with wild type or mutated HBV. The altered MGST2 and HIF1A were found only with mutated HBV. The rtM204I/sW196* preS/S truncation may endorse the cell transformation and tumorigenesis ability via altered host gene expressions, including MGST2, HIF1A, and TGFbi. Downregulated TGFbi may be a common mechanism for oncogenicity in HBV surface truncation mutants.

Characterization of hepatitis B virus infection and viral DNA integration in non-Hodgkin lymphoma

Hepatitis B virus (HBV) infection has been reported to be associated with non-Hodgkin lymphoma (NHL). However, the evidence is limited to the seroepidemiological study. There is a lack of evidence showing the HBV infection and integration in NHL cells. Here, we reported that in the Shanghai area, the positive rates of serum HBsAg (OR: 3.11; 95% CI: 2.20-4.41) and HBeAg (OR: 3.99; 95% CI: 1.73-9.91) were significantly higher in patients with NHL. HBsAg, HBcAg and HBV DNA were detected in 34.4%, 45.2% and 47.0% of the NHL tissues, respectively. Furthermore, by using a high-throughput viral integration detection approach (HIVID), integrated HBV DNA was identified from 50% (6/12) HBV-related NHL tissues. There were a total of 313 HBV integration sites isolated from the NHL tissues, among which four protein-coding genes (FAT2, SETX, ITGA10 and CD63) were interrupted by HBV DNA in their exons. Seven HBV preferential target genes (ANKS1B, HDAC4, EGFLAM, MAN1C1, XKR6, ZBTB38 and CCDC91) showed significantly altered expression levels in NHL, suggesting a potential role of these genes in NHL development. Taken together, HBV integration is a common phenomenon in NHL. This finding opens up a new direction of research into the mechanistic link between HBV infection and NHL.

Immune-Escape Hepatitis B Virus Mutations Associated with Viral Reactivation upon Immunosuppression

Hepatitis B virus (HBV) reactivation occurs as a major complication of immunosuppressive therapy among persons who have recovered from acute hepatitis and those who have controlled chronic infection. Recent literature data emphasize the presence of a high degree of S gene variability in HBV isolates from patients who developed reactivation. In reactivated HBV, the most frequently detected mutations belong to the second loop of “a” determinant in HBsAg. These mutations were identified to be immune escape and responsible for vaccine- and diagnostic-escape phenomena. Their emergence clearly provides survival in the presence of a developed humoral immune response and is often associated with impaired serological diagnosis of HBV reactivation. The knowledge of their existence and roles can elucidate the process of reactivation and strongly highlights the importance of HBV DNA detection in monitoring all patients with a history of HBV infection who are undergoing immunosuppression. This review discusses the possible influence of the most frequently found immune-escape mutations on HBV reactivation.

Quantification of large and middle proteins of hepatitis B virus surface antigen (HBsAg) as a novel tool for the identification of inactive HBV carriers

OBJECTIVE

Among individuals with chronic hepatitis B, those with hepatitis B e-antigen (HBeAg)-negative chronic hepatitis (CHB) can be difficult to distinguish from those with HBeAg-negative chronic HBV infection, also referred to as inactive HBV carriers (ICs), but both require different medical management. The level of HBV surface antigen (HBsAg) has been proposed as a marker to discriminate between chronic infection and hepatitis stages. HBsAg consists of large, middle and small HBs. The aim of this study was to determine whether the composition of HBsAg improved the identification of ICs among HBsAg-positive subjects with different phases of HBV infections.

DESIGN

HBV large surface proteins (LHBs) and HBV middle surface proteins (MHBs) were quantified in serum samples from 183 clinically well-characterised untreated patients with acute (n=14) HBV infection, ICs (n=44), CHBs (n=46), chronic HBeAg-positive phase (n=68) and hepatitis delta coinfection (n=11) using an ELISA, with well-defined monoclonal antibodies against the preS1 domain (LHBs) and the preS2-domain (MHBs). A Western blot analysis was used to verify the quantitation of the components of HBsAg. Total HBsAg was quantified using a modified commercially available assay (HBsAg V.6.0, Enzygnost, Siemens, Erlangen).

RESULTS

The composition of HBsAg showed specific patterns across different phases of hepatitis B. Individuals in the IC phase had significantly lower proportions of LHBs and MHBs than patients in acute or chronic phases irrespective of their HBV e-antigen status (p<0.0001) or HBsAg level. Both LHBs and MHBs ratios better predicted the IC phase than total HBsAg levels.

CONCLUSION

Quantification of MHBs, particularly LHBs represents a novel tool for the identification of the IC stage.

Intrahepatic hepatitis B virus large surface antigen induces hepatocyte hyperploidy via failure of cytokinesis

Hepatitis B virus (HBV) is an aetiological factor for liver cirrhosis and hepatocellular carcinoma (HCC). Despite current antiviral therapies that successfully reduce the viral load in patients with chronic hepatitis B, persistent hepatitis B surface antigen (HBsAg) remains a risk factor for HCC. To explore whether intrahepatic viral antigens contribute directly to hepatocarcinogenesis, we monitored the mitotic progression of HBV-positive cells. Cytokinesis failure was increased in HBV-positive HepG2.2.15 and 1.3ES2 cells, as well as in HuH-7 cells transfected with a wild-type or X-deficient HBV construct, but not in cells transfected with an HBsAg-deficient construct. We show that expression of viral large surface antigen (LHBS) was sufficient to induce cytokinesis failure of immortalized hepatocytes. Premitotic defects with DNA damage and G2 /M checkpoint attenuation preceded cytokinesis in LHBS-positive cells, and ultimately resulted in hyperploidy. Inhibition of polo-like kinase-1 (Plk1) not only restored the G2 /M checkpoint in these cells, but also suppressed LHBS-mediated in vivo tumourigenesis. Finally, a positive correlation between intrahepatic LHBS expression and hepatocyte hyperploidy was detected in >70% of patients with chronic hepatitis B. We conclude that HBV LHBS provokes hyperploidy by inducing DNA damage and upregulation of Plk1; the former results in atypical chromatin structures, and the latter attenuates the function of the G2 /M DNA damage checkpoint. Our data uncover a mechanism by which genomic integrity of hepatocytes is disrupted by viral LHBS. These findings highlight the role of intrahepatic surface antigen as an oncogenic risk factor in the development of HCC. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Review article: the prevention of hepatitis B-related hepatocellular carcinoma

BACKGROUND

Ample evidence indicates an aetiological association of persistent hepatitis B virus (HBV) infection with hepatocellular carcinoma (HCC). Several viral, host and external risk factors for the development of HBV-related HCC have been documented.

AIMS

To summarise and discuss the risk stratification and the preventive strategies of HBV-related HCC.

METHODS

Recent published studies identified from PubMed were comprehensively reviewed. The key words included chronic hepatitis B, HBV, hepatocellular carcinoma, prevention and antiviral therapy.

RESULTS

The incidence of HCC is extremely high in HBV hyperendemic areas. For HBV patients left untreated, significant risk factors for HCC include male gender, aging, advanced hepatic fibrosis, persistent serum transaminase elevation, specific HBV entry receptor (NTCP) genotype, PM2.5 exposure, HBeAg positivity, HBV genotype C/D/F, high proportion of core promoter mutation, pre-S deletion, high serum levels of HBV DNA and HBsAg as well as co-infection with HCV, HDV and HIV. Primary prevention of HBV-related HCC can be achieved through universal HBV vaccination and anti-viral prophylaxis for high viraemic mothers. The goal of secondary prevention has been reached by effective anti-viral therapy to reduce the risk of HCC development in chronic hepatitis B patients. However, whether HCC is prevented or delayed deserves further examination. Finally, several studies confirmed the tertiary preventive effect of anti-viral therapy in reducing risk of HCC recurrence after curative therapies.

CONCLUSIONS

Through the strategies of three-level prevention, the global burden of HBV-related HCC should decline over time and even be eliminated in conjunction with HBV cure.

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

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

Reactivation of a Vaccine Escape Hepatitis B Virus Mutant in a Cambodian Patient During Anti-Hepatitis C Virus Therapy

A 76-year-old Cambodian man co-infected with hepatitis B virus (HBV) and hepatitis C virus (HCV) 6c-1 presented for care. HBV DNA was intermittently detectable despite anti-HBs levels being above the protective threshold. During treatment for HCV, HBV DNA levels increased. Sequencing revealed multiple mutations including vaccine escape mutation and mutations predicted to enhance fitness. This case represents exacerbation of an HBV vaccine escape mutant during a direct-acting antiviral therapy.

Prediction value of serum HBV large surface protein in different phases of HBV infection and virological response of chronic hepatitis B patients

BACKGROUND

Serum HBV large surface protein (HBV-LP) is an envelope protein that has a close relationship with HBV DNA level. This study is to explore the prediction value of HBV-LP in different phase of HBV infection and during antiviral therapy in chronic hepatitis B (CHB) patients.

METHODS

A retrospective study was conducted in 2033 individuals, which included 1677 HBV infected patients in different phases and 356 healthy controls. HBV-LP, HBV serum markers and HBV DNA were detected by ELISA, CMIA and qRT-PCR, respectively. 85 CHB patients receiving PegIFNα or ETV were divided into virological response (VR) and partial virological response (PVR). The dynamic changes of HBV DNA and HBV-LP were observed.

RESULTS

The level of HBV-LP in 2033 individuals was shown as: HBeAg-positive hepatitis > HBeAg-positive infection > HBeAg-negative hepatitis > HBeAg-negative infection > healthy controls. HBV-LP was positive in all patients whose HBV DNA > 1.0E + 06 IU/ml. When HBsAg was <0.05 IU/ml or >1000 IU/ml, HBV DNAs were all negative if HBV-LP < 1.0 S/CO. When HBsAg was between 0.05 IU/ml and 1000 IU/ml, the consistency of HBV-LP with HBV DNA was 100% in case of HBV-LP > 4.0 S/CO in HBeAg-positive patients and HBV-LP > 2.0 S/CO in HBeAg-negative ones. During antiviral therapy, baseline HBV-LP was lower in VR patients than that in PVR patients. The optimal cut-off points to predict VR by baseline HBV-LP were 32.4 and 28.6 S/CO for HBeAg-positive and HBeAg-negative hepatitis patients, respectively.

CONCLUSIONS

HBV-LP may be a useful marker for distinguishing the different phases of HBV infection. Moreover, baseline HBV-LP level can be used for predicting VR of CHB patients.

Correlation between HBV protein preS2 and tumor markers of hepatocellular carcinoma

BACKGROUND

Alpha-fetoprotein (AFP) and Glypican 3 (GPC3) are both oncogenes and reactivated in hepatocellular carcinoma (HCC). PreS2 has been proved to be an important transactivator in HCC. In this study, we aim to provide evidence that HBV protein preS2 is responsible for AFP and GPC3's reactivation in HCC.

METHODS

Totally Sixty-three cases of HCC, aged 34-79, who were surgically treated and pathologically confirmed were enrolled. The levels of AFP in peripheral serum were detected with electrochemical luminescence method before surgery. Levels of GPC3 in HCC samples were evaluated by immunohistochemistry. Luciferase reporter assays were used to measure the effect of preS2 on AFP and GPC3 promoters.

RESULTS

AFP level and GPC3 but not albumin were significantly higher in preS2-positive HCC samples than preS2-negative HCC samples. And the preS2 protein expression was positively related with serum AFP level and GPC3 expression. Furtherly, dual luciferase assay showed that preS2 activated AFP and GPC3 promoter activity.

CONCLUSION

The expression of preS2 protein relates closely to HCC markers AFP and GPC3.

Hepatitis B virus PreS1 facilitates hepatocellular carcinoma development by promoting appearance and self-renewal of liver cancer stem cells

Hepatitis B virus (HBV) is a major etiologic agent of hepatocellular carcinoma (HCC). However, the molecular mechanism by which HBV infection contributes to HCC development is not fully understood. Here, we initially showed that HBV stimulates the production of cancer stem cells (CSCs)-related markers (CD133, CD117 and CD90) and CSCs-related genes (Klf4, Sox2, Nanog, c-Myc and Oct4) and facilitates the self-renewal of CSCs in human hepatoma cells. Cellular and clinical studies revealed that HBV facilitates hepatoma cell growth and migration, enhances white blood cell (WBC) production in the sera of patients, stimulates CD133 and CD117 expression in HCC tissues, and promotes the CSCs generation of human hepatoma cells and clinical cancer tissues. Detailed studies revealed that PreS1 protein of HBV is required for HBV-mediated CSCs generation. PreS1 activates CD133, CD117 and CD90 expression in normal hepatocyte derived cell line (L02) and human hepatoma cell line (HepG2 and Huh-7); facilitates L02 cells migration, growth and sphere formation; and finally enhances the abilities of L02 cells and HepG2 cells to induce tumorigeneses in nude mice. Thus, PreS1 acts as a new oncoprotein to play a key role in the appearance and self-renewal of CSCs during HCC development.

Nucleos(t)ide analogues causes HBV S gene mutations and carcinogenesis

BACKGROUND

The long-term use of nucleos(t)ide analogues causes drug resistance and mutations in the HBV reverse transcriptase (RT) region of the polymerase gene. The RT region overlaps the HBV surface gene (S gene) and therefore, the mutations in the RT region simultaneously modify S gene sequence. Certain mutations in the RT region bring about truncated S proteins because the corresponding changed S gene encodes a stop codon which results in the loss of a large portion of the C-terminal hydrophobic region of HBV surface protein. The rtA181T/sW172*, rtM204I/sW196* and rtV191I/sW182* are the most frequently reported drug-resistant mutations with C-terminal truncation, these mutations have oncogenic potential.

DATA SOURCES

PubMed and Web of Science were searched using terms: "hepatitis B virus", "HBV drug resistance mutation", "HBV surface protein", "HBV truncation", "hepatocellular carcinoma", "rtA181T/sW172*", "rtM204I/sW196*", "rtV191I/sW182*", and relevant articles published in English in the past decades were reviewed.

RESULTS

The rtA181T/sW172* and rtV191I/sW182* mutants occurred more frequently than the rtM204I/sW196* mutant both in chronic hepatitis B patients and the HBV-related hepatocellular carcinoma tissues. Although these mutations occur naturally, nucleos(t)ide analogues therapy is the main driving force. These mutations may exist alone or coexist with other HBV mutations. All these three mutants impair the virion secretion and result in HBV surface protein retention and serum HBV DNA level reduction. These mutations possess potential carcinogenic properties. The three mutations are resistant to more than one nucleos(t)ide analogue and therefore, it is difficult to treat the patients with the truncated mutations.

CONCLUSIONS

Nucleos(t)ide analogues induce drug resistance and HBV S gene truncated mutations. These mutations have potential carcinogenesis.

Evolution in Our Understanding of Hepatitis B Virus Virology and Immunology

Hepatitis B virus (HBV) infection is a major global health challenge. HBV can cause significant morbidity and mortality by establishing acute and chronic hepatitis. Approximately 250 million people worldwide are chronically infected, and more than 2 billion people have been exposed to HBV. Since the discovery of HBV, the advances in our understanding of HBV virology and immunology have translated into effective vaccines and therapies for HBV infection. Although current therapies successfully suppress viral replication but rarely succeed in viral eradication, recent discoveries in HBV virology and immunology provide exciting rationales for novel treatment strategies aiming at HBV cure.

Genomic and oncogenic preference of HBV integration in hepatocellular carcinoma

Hepatitis B virus (HBV) can integrate into the human genome, contributing to genomic instability and hepatocarcinogenesis. Here by conducting high-throughput viral integration detection and RNA sequencing, we identify 4,225 HBV integration events in tumour and adjacent non-tumour samples from 426 patients with HCC. We show that HBV is prone to integrate into rare fragile sites and functional genomic regions including CpG islands. We observe a distinct pattern in the preferential sites of HBV integration between tumour and non-tumour tissues. HBV insertional sites are significantly enriched in the proximity of telomeres in tumours. Recurrent HBV target genes are identified with few that overlap. The overall HBV integration frequency is much higher in tumour genomes of males than in females, with a significant enrichment of integration into chromosome 17. Furthermore, a cirrhosis-dependent HBV integration pattern is observed, affecting distinct targeted genes. Our data suggest that HBV integration has a high potential to drive oncogenic transformation.

Hepatitis B infection is a risk factor for hepatocellular carcinoma. Here, the authors characterise viral infection in a cohort of hepatocellular carcinoma patients and find viral integration is more frequent in males than females.

Canonical NF-κB signaling in hepatocytes acts as a tumor-suppressor in hepatitis B virus surface antigen-driven hepatocellular carcinoma by controlling the unfolded protein response

Chronic hepatitis B virus (HBV) infection remains the most common risk factor for hepatocellular carcinoma (HCC). Efficient suppression of HBV viremia and necroinflammation as a result of nucleos(t)ide analogue treatment is able to reduce HCC incidence; nevertheless, hepatocarcinogenesis can occur in the absence of active hepatitis, correlating with high HBV surface antigen (HBsAg) levels. Nuclear factor κB (NF-κB) is a central player in chronic inflammation and HCC development. However, in the absence of severe chronic inflammation, the role of NF-κB signaling in HCC development remains elusive. As a model of hepatocarcinogenesis driven by accumulation of HBV envelope polypeptides, HBsAg transgenic mice, which show no HBV-specific immune response, were crossed to animals with hepatocyte-specific inhibition of canonical NF-κB signaling. We detected prolonged, severe endoplasmic reticulum stress already at 20 weeks of age in NF-κB-deficient hepatocytes of HBsAg-expressing mice. The unfolded protein response regulator binding immunoglobulin protein/78-kDa glucose-regulated protein was down-regulated, activating transcription factor 6, and eIF2α were activated with subsequent overexpression of CCAAT/enhancer binding protein homologous protein. Notably, immune cell infiltrates and liver transaminases were unchanged. However, as a result of this increased cellular stress, insufficient hepatocyte proliferation due to G1 /S-phase cell cycle arrest with overexpression of p27 and emergence of ductular reactions was detected. This culminated in increased DNA damage already at 20 weeks of age and finally led to 100% HCC incidence due to NF-κB inhibition.

CONCLUSION

The role of canonical NF-κB signaling in HCC development depends on the mode of liver damage; in the case of HBsAg-driven hepatocarcinogenesis, NF-κB in hepatocytes acts as a critical tumor suppressor by augmenting the endoplasmic reticulum stress response.

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.

HBx triggers either cellular senescence or cell proliferation depending on cellular phenotype

Replicative senescence is a hallmark of chronic liver diseases including chronic hepatitis B virus (HBV) infection, whereas HBV-encoded oncoproteins HBx and preS2 have been found to overcome senescence. HBx possesses a C-terminal truncation mainly in hepatocellular carcinomas but also in noncancerous liver tissues. Here, by cell counting, BrdU incorporation, MTT proliferation assay, cell cycle analysis, SA-βgal staining and Western blotting in primary and malignant cells, we investigated the effect of HBx C-terminal mutants on cellular senescence. HBx C-terminal mutants were found to trigger cellular senescence in primary MRC5 cells, and malignant liver cells Huh7, and SK-Hep1. In contrast, these mutants promoted the proliferation of HepG2 malignant liver cells. The pro-senescent effect of HBx relied on an increased p16(INK4a) and p21(Waf1/Cip1) expression, and a decreased phosphorylation of Rb. Together, these results suggest that the two main variants of HBx present in HBV-infected liver possess opposite effects on cellular senescence that depend on the phenotype of infected cells.

Oncogenic potential of hepatitis B virus encoded proteins

Due to the limited treatment options hepatocellular carcinoma (HCC) is one of the leading causes of cancer related death, and hepatitis B virus (HBV) infection is the major risk factor for development of HCC worldwide. HCC is typically preceded by chronic inflammation, but may also develop in the absence of liver disease on the basis of HBV infection and even when virus replication is controlled by antivirals. In this situation, HBV antigen expression persists and direct oncogenic effects of HBV are integration of the viral DNA into the host genome as well as direct effects of viral proteins. These factors have to be taken into account in order to personalize HCC surveillance in CHB and unravel novel therapeutic approaches.

Clinical relevance of hepatitis B virus variants

The hepatitis B virus (HBV) is a global public health problem with more than 240 million people chronically infected worldwide, who are at risk for end-stage liver disease and hepatocellular carcinoma. There are an estimated 600000 deaths annually from complications of HBV-related liver disease. Antiviral therapy with nucleos/tide analogs (NA) targeting the HBV polymerase (P) can inhibit disease progression by long-term suppression of HBV replication. However, treatment may fail with first generation NA therapy due to the emergence of drug-resistant mutants, as well as incomplete medication adherence. The HBV replicates via an error-prone reverse transcriptase leading to quasispecies. Due to overlapping open reading frames mutations within the HBV P can cause concomitant changes in the HBV surface gene (S) and vice versa. HBV quasispecies diversity is associated with response to antiviral therapy, disease severity and long-term clinical outcomes. Specific mutants have been associated with antiviral drug resistance, immune escape, liver fibrosis development and tumorgenesis. An understanding of HBV variants and their clinical relevance may be important for monitoring chronic hepatitis B disease progression and treatment response. In this review, we will discuss HBV molecular virology, mechanism of variant development, and their potential clinical impact.

Genetic and epigenetic alterations in hepatitis B virus-associated hepatocellular carcinoma

Hepatitis B virus (HBV) is a major cause of hepatocellular carcinoma (HCC). Its chronic infection can lead to chronic liver inflammation and the accumulation of genetic alterations to result in the oncogenic transformation of hepatocytes. HBV can also sensitize hepatocytes to oncogenic transformation by causing genetic and epigenetic changes of the host chromosomes. HBV DNA can insert into host chromosomes and recent large-scale whole-genome sequencing studies revealed recurrent HBV DNA integrations sites that may play important roles in the initiation of hepatocellular carcinogenesis. HBV can also cause epigenetic changes by altering the methylation status of cellular DNA, the post-translational modification of histones, and the expression of microRNAs. These changes can also lead to the eventual hepatocellular transformation. These recent findings on the genetic and epigenetic alterations of the host chromosomes induced by HBV opened a new avenue for the development of novel diagnosis and treatments for HBV-induced HCC.

Single nucleotide mapping of RNA 5' and 3' ends

Nuclease protection assay is a sensitive method for detection, quantitation, and mapping of a specific RNA in an extremely heterogeneous mixture of RNAs, such as total cellular RNA. The assay is based on a small volume solution hybridization of a single-stranded synthetic antisense and labeled RNA probe to a RNA sample. Thus, it is much more efficient than the common immobilized hybridization on a membrane, such as in northern-blot analysis. After solution hybridization, different nucleases are used to remove any remaining single-stranded nucleotides within the probe and sample RNA by digestion. Then, the remaining probe-target hybrids are purified and separated on a denaturing polyacrylamide gel. Using a radioactive labeled probe, the protected probe can be visualized by direct autoradiography and the copy number can be calculated based on the specific radioactivity of the RNA probe and the length of protected fragment. Because of its high sensitivity and resolution, nuclease protection assay is the most effective procedure for mapping internal and external boundaries in mRNA compared to other RNA detection methods such as RT-PCR.

The direct and indirect roles of HBV in liver cancer: prospective markers for HCC screening and potential therapeutic targets

Chronic hepatitis B virus (HBV) infection remains the number one risk factor for hepatocellular carcinoma (HCC), accounting for more than 600 000 deaths/year. Despite highly effective antiviral treatment options, chronic hepatitis B (CHB), subsequent end-stage liver disease and HCC development remain a major challenge worldwide. In CHB, liver damage is mainly caused by the influx of immune cells and destruction of infected hepatocytes, causing necro-inflammation. Treatment with nucleoside/nucleotide analogues can effectively suppress HBV replication in patients with CHB and thus decrease the risk for HCC development. Nevertheless, the risk of HCC in treated patients showing sufficient suppression of HBV DNA replication is significantly higher than in patients with inactive CHB, regardless of the presence of baseline liver cirrhosis, suggesting direct, long-lasting, predisposing effects of HBV. Direct oncogenic effects of HBV include integration in the host genome, leading to deletions, cis/trans-activation, translocations, the production of fusion transcripts and generalized genomic instability, as well as pleiotropic effects of viral transcripts (HBsAg and HBx). Analysis of these viral factors in active surveillance may allow early identification of high-risk patients, and their integration into a molecular classification of HCC subtypes might help in the development of novel therapeutic approaches.

Hepatitis B virus PreS/S gene variants: pathobiology and clinical implications

The emergence and takeover of hepatitis B virus (HBV) variants carrying mutation(s) in the preS/S genomic region is a fairly frequent event that may occur spontaneously or may be the consequence of immunoprophylaxis or antiviral treatments. Selection of preS/S mutants may have relevant pathobiological and clinical implications. Both experimental data and studies in humans show that several specific mutations in the preS/S gene may induce an imbalance in the synthesis of the surface proteins and their consequent retention within the endoplasmic reticulum (ER) of the hepatocytes. The accumulation of mutated surface proteins may cause ER stress with the consequent induction of oxidative DNA damage and genomic instability. Viral mutants with antigenically modified surface antigen may be potentially infectious to immune-prophylaxed patients and may account for cases of occult HBV infection. In addition, preS/S variants were reported to be associated with cases of fulminant hepatitis as well as of fibrosing cholestatic hepatitis, and they are associated with cirrhosis and hepatocellular carcinoma development.

Transactivation of proto-oncogene c-Myc by hepatitis B virus transactivator MHBst167

C-terminally truncated hepatitis B virus (HBV) middle size surface proteins (MHBs^t) has been shown to be a transcriptional activator and may be relevant to hepatocarcinogenesis by transactivating gene expression. In the present study, a pcDNA3.1(-)-MHBs^t167 vector coding for MHBs^t truncated at amino acid 167 (MHBs^t167) was constructed and transfected into the HepG2 hepatoma cell line. mRNA and protein expression of MHBs^t167 in the cells was detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis. A cDNA library of genes transactivated by the truncated protein in HepG2 cells was made in pGEM-T Easy using suppression subtractive hybridization. The cDNAs were sequenced and analyzed with BLAST searching against the sequences in GenBank. The results showed that certain sequences, such as that of human proto-oncogene c-Myc, may be involved in tumor development. An expression vector pCAT3/c-Myc containing the chloramphenicol acetyltransferase (CAT) gene under the control of a c-Myc promoter was generated, and the transcriptional transactivating effect of MHBs^t167 on the c-Myc promoter was investigated by RT-PCR and western blotting. MHBs^t167 was found to upregulate the transcriptional activity of the promoter, as well as transcription and translation of c-Myc. MHBs^t167 was also shown to transactivate SV40 immediate early promoter, and transcriptionally transactivate the expression of human c-Myc. These findings provide new directions for studying the biological functions of MHBs^t167, and for a better understanding of the tumor development mechanisms of HBV infection.

Screening of hepatocyte proteins binding with the middle surface protein of the hepatitis B virus by the yeast two-hybrid system

The effect of the middle hepatitis B virus surface protein (MHBs) remains to be elucidated. To investigate the biological function of the MHBs protein, the present study performed yeast two-hybrid screening to search for proteins that interact with the MHBs protein in hepatocytes. The bait plasmid expressing the MHBs protein was constructed by cloning the gene of the MHBs protein into pGBKT7, then the recombinant plasmid DNA was transformed into AH109 yeast (a type). The transformed yeast AH109 was mated with yeast Y187 (α type) containing the liver cDNA library plasmid in 2X yeast peptone dextrose adenine (YPDA) medium. The mated diploid yeast was plated on quadruple dropout medium (SD/-Trp-Leu-His-Ade) containing X-α-gal for selection and screening. Following extracting and sequencing of the plasmids from positive (blue) colonies, the sequence analysis was conducted and analyzed by bioinformatics methods. Two colonies were selected and sequenced. Among them, one was the human DNA sequence from the clone RP11-490D19 on chromosome 9 and the other was homo sapiens 12 BAC RP11-180M15 (Roswell Park Cancer Institute Human BAC Library). The yeast two-hybrid system is an effective method for identifying hepatocyte proteins that interact with MHBs. The MHBs protein binds with different proteins suggesting that it has multiple functions in vivo.

Identification of transforming hepatitis B virus S gene nonsense mutations derived from freely replicative viruses in hepatocellular carcinoma

Background & Aims

The correlation between chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) has been well-established. But the roles of viral factor remain uncertain. Only HBV X gene and nonsense mutations of S gene (C-terminal truncation of HBV surface protein) have been demonstrated to have transforming activity. Whether they play a significant role in hepatocarcinogenesis is still uncertain.

Methods

Twenty-five HBV-related HCC patients were positive for hepatitis B core antigen (HBcAg) in the cancerous parts of their HCC liver tissues by immunohistochemistry studies, and had available tissue for whole HBV genome sequence analysis. The results were compared with 25 gender and age-matched HBcAg negative HCCs. Plasmids encoding HBV S gene nonsense mutations identified from HBcAg (+) HCC tissue were constructed to investigate their cell proliferation, transformation activity and the oncogenic potentials by xenograft study and in vivo migration assay.

Results

HBcAg (+) HCC patients were significantly associated with cirrhosis and small tumor size (≦2 cm) when compared with HBcAg (−) HCC patients. Southern blot analyses revealed freely replicative forms of HBV in the cancerous parts of HBcAg(+) HCC. Three nonsense mutations of S gene (sL95*, sW182*, and sL216*) were identified in the HBcAg(+) HCC tumor tissues. sW182* and sL216* were recurrently found in the 25 HBcAg (−) HCC tumor tissue, too. Functional studies of the above 3 non-sense mutations all demonstrated higher cell proliferation activities and transformation abilities than wild type S, especially sW182*. Tumorigenicity analysis by xenograft experiments and in vitro migration assay showed potent oncogenic activity of sW182* mutant.

Conclusions

This study has demonstrated potent oncogenic activity of nonsense mutations of HBV S gene, suggesting they may play an important role in hepatocarcinogenesis.

Medical virology of hepatitis B: how it began and where we are now

Infection with hepatitis B virus (HBV) may lead to acute or chronic hepatitis. HBV infections were previously much more frequent but there are still 240 million chronic HBV carriers today and ca. 620,000 die per year from the late sequelae liver cirrhosis or hepatocellular carcinoma. Hepatitis B was recognized as a disease in ancient times, but its etiologic agent was only recently identified. The first clue in unraveling this mystery was the discovery of an enigmatic serum protein named Australia antigen 50 years ago by Baruch Blumberg. Some years later this was recognized to be the HBV surface antigen (HBsAg). Detection of HBsAg allowed for the first time screening of inapparently infected blood donors for a dangerous pathogen. The need to diagnose clinically silent HBV infections was a strong driving force in the development of modern virus diagnostics. HBsAg was the first infection marker to be assayed with a highly sensitive radio immune assay. HBV itself was among the first viruses to be detected by assay of its DNA genome and IgM antibodies against the HBV core antigen were the first to be selectively detected by the anti-μ capture assay. The cloning and sequencing of the HBV genome in 1978 paved the way to understand the viral life cycle, and allowed development of efficient vaccines and drugs. Today’s hepatitis B vaccine was the first vaccine produced by gene technology. Among the problems that still remain today are the inability to achieve a complete cure of chronic HBV infections, the recognition of occult HBV infections, their potential reactivation and the incomplete protection against escape mutants and heterologous HBV genotypes by HBV vaccines.

Hepatitis B surface antigen could contribute to the immunopathogenesis of hepatitis B virus infection

Various findings concerning the clinical significance of quantitative changes in hepatitis B surface antigen (HBsAg) during the acute and chronic phase of hepatitis B virus (HBV) infection have been reported. In addition to being a biomarker of HBV-replication activity, it has been reported that HBsAg could contribute to the immunopathogenesis of HBV persistent infection. Moreover, HBsAg could become an attractive target for immune therapy, since the cellular and humeral immune response against HBsAg might be able to control the HBV replication and life cycle. However, several reports have described the immune suppressive function of HBsAg. HBsAg might suppress monocytes, dendritic cells (DCs), natural killer (NK), and natural killer T (NK-T) cells by direct interaction. On the other hand, cytotoxic T lymphocytes (CTLs) and helper T (Th) cells were exhausted by high amounts of HBsAg. In this paper, we focused on the immunological aspects of HBsAg, since better understanding of the interaction between HBsAg and immune cells could contribute to the development of an immune therapy as well as a biomarker of the state of HBV persistent infection.

HBV-related hepatocellular carcinoma: the role of integration, viral proteins and miRNA

The development of hepatocellular carcinoma during chronic hepatitis B infection is a multifactorial process thought to be a consequence of several direct and indirect mechanisms. In this review we discuss how viral proteins and cycles of ongoing liver damage and regeneration, coupled with HBV DNA integration and aberrant miRNA expression may enhance the risk for the development of hepatocellular carcinoma.

Emergence of the rtA181T/sW172* mutant increased the risk of hepatoma occurrence in patients with lamivudine-resistant chronic hepatitis B

Background

Development of the hepatitis B virus (HBV) rtA181T/sW172* mutant could occur during prolonged lamivudine (LAM) therapy, conferring cross resistance to adefovir. Recent studies demonstrated an increased oncogenic potential of this mutant in NIH3T3 cells. In this study, we aimed to investigate the clinical significance of this finding.

Methods

Serum samples from 123 LAM-resistant chronic hepatitis B patients were submitted for virological assays. A highly sensitive amplification created restriction enzyme site (ACRES) method was devised to detect small amounts of the rtA181T mutant in the serum. Virological factors including HBV-DNA level, genotype, precore G1896A, BCP A1762T/G1764A, rtM204I/V, rtA181T and pre-S internal deletion mutations as well as clinical variables including subsequent use of rescue drugs were submitted for outcome analysis.

Results

By use of the highly sensitive ACRES method, the rtA181T mutant was detectable in 10 of the 123 LAM-resistant patients. During the mean follow-up period of 26.2 ± 16.4 months (range 2 to 108 months), 3 of the 10 (30.0%) rtA181T-positive patients and 2 of the 113 (1.8%) rtA181T-negative patients developed hepatocellular carcinoma (HCC). Kaplan-Meier analysis indicated that the presence of rtA181T mutation (P < 0.001), age > 50 years (P = 0.001), and liver cirrhosis (P < 0.001) were significantly associated with subsequent occurrence of HCC. All 5 HCC patients belonged to the older age and cirrhosis groups.

Conclusions

Emergence of the rtA181T/sW172* mutant in LAM-resistant patients increased the risk of HCC development in the subsequent courses of antiviral therapy.

Hepatitis B virus X gene and hepatocarcinogenesis

Chronic hepatitis B virus (HBV) infection has been identified as a major risk factor in hepatocellular carcinoma (HCC), which is one of the most common cancers worldwide. The pathogenesis of HBV-mediated hepatocarcinogenesis is, however, incompletely understood. Evidence suggests that the HBV X protein (HBx) plays a crucial role in HCC development. HBx is a multifunctional regulator that modulates transcription, signal transduction, cell cycle progression, apoptosis, protein degradation pathways, and genetic stability through interaction with host factors. This review describes the current state of knowledge of the molecular pathogenesis of HBV-induced HCC, with a focus on the role of HBx in hepatocarcinogenesis.

Hepatitis B and C virus hepatocarcinogenesis: lessons learned and future challenges

Worldwide, hepatocellular carcinoma (HCC) is one of the most common cancers. It is thought that 80% of hepatocellular carcinomas are linked to chronic infections with the hepatitis B (HBV) or hepatitis C (HCV) viruses. Chronic HBV and HCV infections can alter hepatocyte physiology in similar ways and may utilize similar mechanisms to influence the development of HCC. There has been significant progress towards understanding the molecular biology of HBV and HCV and identifying the cellular signal transduction pathways that are altered by HBV and HCV infections. Although the precise molecular mechanisms that link HBV and HCV infections to the development of HCC are not entirely understood, there is considerable evidence that both inflammatory responses to infections with these viruses, and associated destruction and regeneration of hepatocytes, as well as activities of HBV- or HCV-encoded proteins, contribute to hepatocyte transformation. In this review, we summarize progress in defining mechanisms that may link HBV and HCV infections to the development of HCC, discuss the challenges of directly defining the processes that underlie HBV- and HCV-associated HCC, and describe areas that remain to be explored.

Oncogenetic tree modeling of human hepatocarcinogenesis

Classical comparative genomic hybridization (CGH) has been used to identify recurrent genomic alterations in human HCC. As hepatocarcinogenesis is considered as a stepwise process, we applied oncogenetic tree modeling on all available classical CGH data to determine occurrence of genetic alterations over time. Nine losses (1p, 4q, 6q, 8p, 9p, 13q, 16p, 16q and 17p) and ten gains (1q, 5p, 6p, 7p, 7q, 8q, 17q, 20p, 20q and Xq) of genomic information were used to build the oncogenetic tree model. Whereas gains of 1q and 8q together with losses of 8p formed a cluster that represents early etiology-independent alterations, the associations of gains at 6q and 17q as well as losses of 6p and 9p were observed during tumor progression. HBV-induced HCCs had significantly more chromosomal aberrations compared to HBV-negative tumors. Losses of 1p, 4q and 13q were associated with HBV-induced HCCs, whereas virus-negative HCCs showed an association of gains at 5p, 7, 20q and Xq. Using five aberrations that were significantly associated with tumor dedifferentiation a robust progression model of stepwise human hepatocarcinogensis (gain 1q → gain 8q → loss 4q → loss 16q → loss 13q) was developed. In silico analysis revealed that protumorigenic candidate genes have been identified for each recurrently altered hotspot. Thus, oncogenic candidate genes that are coded on chromosome arms 1q and 8q are promising targets for the prevention of malignant transformation and the development of biomarkers for the early diagnosis of human HCC that may significantly improve the treatment options and thus prognosis of HCC patients.

A matched case-control study of hepatitis B virus mutations in the preS and core promoter regions associated independently with hepatocellular carcinoma

This study aimed to determine hepatitis B virus (HBV) mutations associated independently with the risk of hepatocellular carcinoma (HCC), as adjusted with other mutations in the preS and core promoter regions of HBV genotypes B and C. One hundred and forty HBV-infected patients with HCC and 280 HBV-infected patients without HCC who had intact data of HBV genotyping and DNA sequencing in both regions were involved in this age-, sex-matched case-control study. Univariate and two-step stepwise multivariate regression analyses were performed to determine factors associated with the risk of HCC. Of 39 mutations evaluated, 23 in genotype C and 6 in genotype B were associated with an increased risk of HCC in the univariate analysis. Multivariate analyses established that genotype C (adjusted odds ratio [AOR] = 3.3; 95% confidence interval [CI] = 1.1-9.8), viral load (≥10(4) copies/ml) (AOR = 2.4; 95% CI = 1.0-5.8), A2962G (AOR = 18.7; 95% CI = 7.5-46.7), preS2 start codon mutation (AOR = 12.5; 95% CI = 3.4-45.5), C105T (AOR = 0.1; 95% CI = 0.0-0.2), T1753V (AOR = 3.1; 95% CI = 1.1-9.2), and A1762T/G1764A (AOR = 2.9; 95% CI = 1.1-7.3) were associated independently with HCC, adjusted for factors including mutations in both regions. By using an estimating haplotype frequencies program, it was found that a haplotypic carriage with 105C and 2962G was significantly more frequent in the patients with HCC than in those without HCC and the frequency of haplotype 2962G-preS2 start codon wildtype-105C-1762T/1764A was 47.9% in the patients with HCC and 4.3% in those without HCC. Conclusively, A2962G and T105C are novel factors associated independently with HCC. Further prospective studies are needed to confirm the role of these mutations in the development of HCC.

Molecular genetics of HBV infection

HBV has evolved a unique life cycle that results in the production of enormous viral loads during active replication without actually killing the infected cells directly. Two of the key events in the viral life cycle of HBV involve firstly the generation of a covalently closed circular (ccc)DNA transcriptional template, either from input genomic DNA or newly replicated capsid-associated DNA, and secondly, reverse transcription of the viral pregenomic (pg)RNA to form progeny HBV DNA genomes. New data are emerging regarding the epigenetic control of cccDNA, which might represent another key factor involved in the pathogenesis and natural history of the disease. Because HBV uses reverse transcription to copy its genome, mutant viral genomes emerge frequently. Particular selection pressures, both endogenous (host immune clearance) and exogenous (vaccines and antiviral drugs), readily select out these escape mutants. The particular viral mutations or combination of mutations that directly affect the clinical outcome of infection are not known; however, four major 'pathways' of antiviral drug resistance-associated substitutions have now been identified. Further studies are clearly needed to identify the pathogenetic basis and clinical sequelae arising from the selection of these particular mutants. In the clinical context of antiviral drug resistance, treating physicians need to adopt therapeutic strategies that effectively control viral replication. Finally, the role of host genetics in influencing the outcome of HBV disease in the context of natural history and therapy is beginning to aid understanding in pathogenesis and, when this knowledge is linked to pathogen-specific databases, this should translate into more individualized patient care.