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ObjectiveThe HBV HBx regulatory protein is required for transcription from the covalently closed circular DNA (cccDNA) minichromosome and affects the epigenetic control of both viral and host cellular chromatin.DesignWe explored, in relevant cellular models of HBV replication, the functional consequences of HBx interaction with DLEU2, a long non-coding RNA (lncRNA) expressed in the liver and increased in human hepatocellular carcinoma (HCC), in the regulation of host target genes and the HBV cccDNA.ResultsWe show that HBx binds the promoter region, enhances the transcription and induces the accumulation of DLEU2 in infected hepatocytes. We found that nuclear DLEU2 directly binds HBx and the histone methyltransferase enhancer of zeste homolog 2 (EZH2), the catalytic active subunit of the polycomb repressor complex 2 (PRC2) complex. Computational modelling and biochemical evidence suggest that HBx and EZH2 share two preferential binding sites in DLEU2 intron 1. HBx and DLEU2 co-recruitment on the cccDNA displaces EZH2 from the viral chromatin to boost transcription and viral replication. DLEU2-HBx association with target host promoters relieves EZH2 repression and leads to the transcriptional activation of a subset of EZH2/PRC2 target genes in HBV-infected cells and HBV-related HCCs.ConclusionsOur results highlight the ability of HBx to bind RNA to impact on the epigenetic control of both viral cccDNA and host genes and provide a new key to understand the role of DLEU2 and EZH2 overexpression in HBV-related HCCs and HBx contribution to hepatocytes transformation.

FZD7 is one of the key players in the subset of WNT-TGFβ-activated hepatocellular carcinomas (HCC), but the consequences of its abnormal expression on hepatocarcinogenesis remain to be better understood. Herein, we aimed to investigate the role of the FZD7-mediated signaling in immature phenotype and aggressiveness of HCC. Firstly, 499 human HCCs were used for clinical and molecular comparisons regarding the expression of FZD7 and s temness-associated markers. We showed that FZD7 overexpression was associated with poor differentiation and, in combination with CD133 , predicted a poor outcome of patients with aggressive recurrence. Next, the impact of WNT3/FZD7 signaling on the differentiation of hepatic cells was assessed in HCC cell lines, as well in the non-transformed progenitor HepaRG cell line and in primary human hepatocytes, transduced with WNT3 and FZD7 -expressing lentiviruses. We demonstrated that the ectopic expression of WNT3 and FZD7 inhibited the differentiation behavior of HepaRG cells and human primary hepatocytes, amplified the pool of EpCAM (+) , CD90 (+) and CD133 (+) subsets of HCC cell lines, and increased their cancer stem cell features. Moreover, we found that WNT3/FZD7-mediated stemness properties of cancer cells were independent of the stemness-associated marker NANOG. In conclusion, we identified the FZD7 (+) /CD133 (+) signature as a potential prognosis marker and molecular therapeutic target, and we strengthened the hypothesis for the involvement of FZD7 in the enrichment of a cancer stem cell pool in HCC.

Backround and aims Complex host-virus interactions account for adaptive and innate immunity dysfunctions and viral cccDNA mini-chromosome persistence, key features of HBV chronicity and challenges for HBV cure. The extent of HBV direct impact on liver transcriptome remains controversial. Transcriptional activation in eukaryotic cells is tightly linked with disruption of nucleosome organization at accessible genomic sites of remodeled chromatin. We sought to investigate the impact of HBV on chromatin accessibility and transcription. Methods We used ATAC-seq (Assay for Transposase Accessible Chromatin followed by high throughput sequencing) to detect early changes in chromatin accessibility coupled with RNA-seq in HBV-infected Primary Human Hepatocytes (PHHs). Results An increasing number of genomic sites change their nucleosome organization over time after HBV infection, with a prevalent, but not exclusive, reduction of chromatin accessibility at specific sites that is partially prevented by inhibiting HBV transcription and replication. ATAC-seq and RNA-seq integration showed that HBV infection impacts on liver fatty acids, bile acids, iron metabolism and liver cancer pathways. The upregulation of iron uptake genes leads to a significant increase of iron content in HBV-infected PHHs whereas iron chelation inhibits cccDNA transcription and viral replication. The chromatin accessibility and transcriptional changes imposed by HBV early after infection persist, as an epigenetic scar, in chronic HBV (CHB) patients and in HBV-related HCCs. These changes are to a large extent independent from viral replication levels and disease activity. Conclusions Altogether our results show that HBV infection impacts on host cell chromatin landscape and specific transcriptional programs including liver metabolism and liver cancer pathways. Re-wiring of iron metabolism boosts viral replication early after infection. The modulation of genes involved in cancer-related pathways may favor the development or the selection of a pro-neoplastic phenotype and persists in HBV-related HCCs.

Primary liver cancer is the sixth most common cancer in men and seventh in women, with hepatocellular carcinoma (HCC) being the most common form (75–85% of primary liver cancer cases) and the most frequent etiology being viral infections (HBV and HCV). In 2020, mortality represented 92% of the incidence—830,180 deaths for 905,677 new cases. Few treatment options exist for advanced or terminal-stage HCC, which will receive systemic therapy or palliative care. Although radiotherapy is used in the treatment of many cancers, it is currently not the treatment of choice for HCC, except in the palliative setting. However, as radiosensitizing drugs, such as inhibitors of DNA repair enzymes, could potentiate the effects of RT in HCC by exploiting the modulation of DNA repair processes found in this tumour type, RT and such drugs could provide a treatment option for HCC. In this review, we provide an overview of PARP1 involvement in DNA damage repair pathway and discuss its potential implication in HCC. In addition, the use of PARP inhibitors and PARP decoys is described for the treatment of HCC and, in particular, in HBV-related HCC.

ObjectiveA convenient, reproducible biomarker of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) transcriptional activity is lacking. We measured circulating HBV RNA (cirB-RNA) in untreated and nucleos(t)ide analogues (NUC) treated chronic hepatitis B (CHB) patients to define its correlation with intrahepatic viral markers and HBV core-related antigen (HBcrAg).DesignPaired liver biopsy and serum samples were collected from 122 untreated and 30 NUC-treated CHB patients. We measured cirB-RNA, HBV DNA, hepatitis B surface antigen (HBsAg), HBcrAg and alanine aminotransferase levels. cirB-RNA was quantified using an investigational HBV RNA assay for use on the cobas 6800 system. The test detects a region spanning the HBV canonical polyadenylation site. cccDNA and 3.5 kb RNA in liver tissue were assessed by quantitative PCR and droplet digital PCR.ResultscirB-RNA was detectable in 100% of HBeAg(+) chronic hepatitis (CH), 57% and 14% of HBeAg(−) CH and chronic infection untreated patients and 47% of NUC-treated patients. cirB-RNA undetectability was associated with lower intrahepatic cccDNA transcriptional activity, as well as serum HBcrAg, but no significant differences in HBsAg, in both untreated and treated patients. In untreated HBeAg(−) patients, cirB-RNA correlated with intrahepatic 3.5 kb RNA and cccDNA transcriptional activity, serum HBV DNA and HBcrAg, but not with HBsAg or total cccDNA levels. Combined undetectability of both cirB-RNA and HBcrAg detection in untreated HBeAg(−) patients identified a subgroup with the lowest levels of intrahepatic transcriptionally active cccDNA.ConclusionOur results support the usefulness of quantification of circulating HBV RNA expressed from cccDNA as an indicator of intrahepatic active viral reservoir in both untreated and NUC-treated CHB patients.Trial registration number NCT02602847.

FZD7 is one of the key players in the subset of WNT-TGFβ-activated hepatocellular carcinomas (HCC), but the consequences of its abnormal expression on hepatocarcinogenesis remain to be better understood. Herein, we aimed to investigate the role of the FZD7-mediated signaling in immature phenotype and aggressiveness of HCC. Firstly, 499 human HCCs were used for clinical and molecular comparisons regarding the expression of FZD7 and stemness-associated markers. We showed that FZD7 overexpression was associated with poor differentiation and, in combination with CD133, predicted a poor outcome of patients with aggressive recurrence. Next, the impact of WNT3/FZD7 signaling on the differentiation of hepatic cells was assessed in HCC cell lines, as well in the non-transformed progenitor HepaRG cell line and in primary human hepatocytes, transduced with WNT3 and FZD7-expressing lentiviruses. We demonstrated that the ectopic expression of WNT3 and FZD7 inhibited the differentiation behavior of HepaRG cells and human primary hepatocytes, amplified the pool of EpCAM(+), CD90(+) and CD133(+) subsets of HCC cell lines, and increased their cancer stem cell features. Moreover, we found that WNT3/FZD7-mediated stemness properties of cancer cells were independent of the stemness-associated marker NANOG. In conclusion, we identified the FZD7(+)/CD133(+) signature as a potential prognosis marker and molecular therapeutic target, and we strengthened the hypothesis for the involvement of FZD7 in the enrichment of a cancer stem cell pool in HCC.

Hepatitis B virus (HBV) represents a major health burden, as it affects close to 290 million people worldwide. Although prophylactic vaccines are available, current therapeutic compounds do not usually achieve HBV eradication due to the persistence of the covalently closed circular (ccc)DNA that serves as viral reservoir. Thus, novel biomarkers that reliably reflect intrahepatic cccDNA transcriptional activity would be highly relevant for the monitoring of infected individuals, as well as the evaluation of new treatments targeting HBV. In this context, the development of 5’ rapid amplification of complementary DNA ends (5’RACE) as a strategy to capture and amplify full-length HBV RNAs, coupled with long-read and full-length sequencing approaches (e.g., Oxford Nanopore Technology), has recently enabled the detailed characterization of these molecules. The analysis of such data requires a dedicated bioinformatics pipeline due to the highly condensed nature of the HBV genome, which is characterized by the production of multiple transcripts and spliced variants that overlap each other. Here, we present Bolero, a computational method and built-in workflow designed to handle HBV sequencing data and evaluate the relative expression of viral RNAs and their spliced variants. The analysis of HBV-infected cell lines demonstrates that our bioinformatics pipeline is efficient for the identification and quantification of individual HBV mRNAs. Thus, Bolero represents a useful tool to study cccDNA transcriptional activity and the heterogeneity of HBV RNA spliced variants. Transcriptomic analyses have brought comprehensive insights in the mechanisms controlling gene expression. Moreover, with the recent advances in sequencing technologies and computational methods, researchers can nowadays not only quantify gene expression, but also study alternative splicing, polyadenylation, transcription initiation, and even rare phenomena such as distant gene fusions. However, conventional analysis tools still rely heavily on the assumption of linear genomes with minimal overlap between open reading frames, rendering them insufficient for studying complex viruses such as hepatitis B virus (HBV). Unlike typical linear genomes, HBV genome consists in a circular DNA molecule, which results in an extensive sequence overlap between its transcripts. To tackle these challenges, we developed an innovative approach coupling 5’ rapid amplification of complementary DNA ends (5’RACE) and long-read sequencing to comprehensively explore the HBV transcriptome. Furthermore, we developed Bolero, a computational method designed to handle the peculiarities of HBV sequencing data, which allows a detailed characterization of the HBV transcriptome.

Infection with Hepatitis B virus (HBV) is a major cause of liver disease and cancer in humans. HBVs (family Hepadnaviridae) have been associated with mammals for millions of years. Recently, the Smc5/6 complex, known for its essential housekeeping functions in genome maintenance, was identified as an antiviral restriction factor of human HBV. The virus has however developed a counteraction mechanism by degrading the complex via its regulatory HBx protein. Whether the antiviral activity of the Smc5/6 complex against hepadnaviruses is an important and evolutionary-conserved function is unknown. Here, we used a combined evolutionary and functional approach to address this question. We first performed phylogenetic and positive selection analyses of the six Smc5/6 complex subunits and found that they have been highly conserved in primates and mammals. Yet, the Smc6 subunit showed marks of adaptive evolution, potentially reminiscent of virus-host 'arms-race'. We then functionally tested the HBx from six very divergent hepadnaviruses now naturally infecting primates, rodents, and bats. Despite little sequence homology, we demonstrate that these HBx efficiently degraded mammalian Smc5/6 complexes, independently of the host species and of the sites under positive selection. Importantly, all also rescued the replication of an HBx-deficient HBV in primary human hepatocytes. These findings point to an evolutionary-conserved requirement for Smc5/6 inactivation by HBx, showing that the Smc5/6 antiviral activity has been an important defense mechanism against hepadnaviruses in mammals. Interestingly, Smc5/6 may further be a restriction factor of other yet unidentified viruses that have driven some of its adaptation.