Association of Hepatitis B Virus Covalently Closed Circular DNA and Human APOBEC3B in Hepatitis B Virus-Related Hepatocellular Carcinoma

APOBEC3 Proteins: From Antiviral Immunity to Oncogenic Drivers in HPV-Positive Cancers

The human APOBEC superfamily consists of eleven cytidine deaminase enzymes. Among them, APOBEC3 enzymes play a dual role in antiviral immunity and cancer development. APOBEC3 enzymes, including APOBEC3A (A3A) and APOBEC3B (A3B), induce mutations in viral DNA, effectively inhibiting viral replication but also promoting somatic mutations in the host genome, contributing to cancer development. A3A and A3B are linked to mutational signatures in over 50% of human cancers, with A3A being a potent mutagen. A3B, one of the first APOBEC3 enzymes linked to carcinogenesis, plays a significant role in HPV-associated cancers by driving somatic mutagenesis and tumor progression. The A3A_B deletion polymorphism results in a hybrid A3A_B gene, leading to increased A3A expression and enhanced mutagenic potential. Such polymorphism has been linked to an elevated risk of certain cancers, particularly in populations where it is more prevalent. This review explores the molecular mechanisms of APOBEC3 proteins, highlighting their dual roles in antiviral defense and tumorigenesis. We also discuss the clinical implications of genetic variants, such as the A3A_B polymorphism, mainly in HPV infection and associated cancers, providing a comprehensive understanding of their contributions to both viral restriction and cancer development.

Viral infection, APOBEC3 dysregulation, and cancer

Viral infection plays a significant role in the development and progression of many cancers. Certain viruses, such as Human Papillomavirus (HPV), Epstein-Barr Virus (EBV), and Hepatitis B and C viruses (HBV, HCV), are well-known for their oncogenic potential. These viruses can dysregulate specific molecular and cellular processes through complex interactions with host cellular mechanisms. One such interaction involves a family of DNA mutators known as APOBEC3 (Apolipoprotein B mRNA Editing Catalytic Polypeptide-like 3). The primary function of these cytidine deaminases is to provide protection against viral infections by inducing viral mutagenesis. However, induction and dysregulation of A3 enzymes, driven by viral infection, can inadvertently lead to cellular DNA tumorigenesis. This review focuses on the current knowledge regarding the interplay between viral infection, A3 dysregulation, and cancer, highlighting the molecular mechanisms underlying this relationship.

Detection of HBV DNA integration in plasma cell-free DNA of different HBV diseases utilizing DNA capture strategy

The landscape of hepatitis B virus (HBV) integration in the plasma cell-free DNA (cfDNA) of HBV-infected patients with different stages of liver diseases [chronic hepatitis B (CHB), liver cirrhosis (LC), and hepatocellular carcinoma (HCC)] remains unclear. In this study, we developed an improved strategy for detecting HBV DNA integration in plasma cfDNA, based on DNA probe capture and next-generation sequencing. Using this optimized strategy, we successfully detected HBV integration events in chimeric artificial DNA samples and HBV-infected HepG2-NTCP cells at day one post infection, with high sensitivity and accuracy. The characteristics of HBV integration events in the HBV-infected HepG2-NTCP cells and plasma cfDNA from HBV-infected individuals (CHB, LC, and HCC) were further investigated. A total of 112 and 333 integration breakpoints were detected in the HepG2-NTCP cells and 22 out of 25 (88%) clinical HBV-infected samples, respectively. In vivo analysis showed that the normalized number of support unique sequences (nnsus) in HCC was significantly higher than in CHB or LC patients (P values ​< ​0.05). All integration breakpoints are randomly distributed on human chromosomes and are enriched in the HBV genome around nt 1800. The majority of integration breakpoints (61.86%) are located in the gene-coding region. Both non-homologous end-joining (NHEJ) and microhomology-mediated end-joining (MMEJ) interactions occurred during HBV integration across the three different stages of liver diseases. Our study provides evidence that HBV DNA integration can be detected in the plasma cfDNA of HBV-infected patients, including those with CHB, LC, or HCC, using this optimized strategy.

Constructing an APOBEC-related gene signature with predictive value in the overall survival and therapeutic sensitivity in lung adenocarcinoma

Background

APOBEC family play an important role in cancer mutagenesis and tumor development. The role of APOBEC family in lung adenocarcinoma (LUAD) has not been studied comprehensively.

Materials and methods

The expression data of pan-cancer as well as LUAD was obtained from public databases. The expression level of APOBEC family genes was analyzed in different normal and cancer tissues. APOBEC mutagenesis enrichment score (AMES) was utilized to evaluate the APOBEC-induced mutations and the relation of APOBEC with genomic instability. Gene set enrichment analysis was used to identify differentially enriched pathways. Univariate Cox regression and Lasso regression were applied to screen key prognostic genes. The immune cell infiltration was estimated by CIBERSORT. RT-qPCR assay, CCK-8 and Transwell assay were conducted to explore gene expression and lung cancer cell invasion.

Results

Cancer tissues had significantly altered expression of APOBEC family genes and the expression patterns of APOBEC family were different in different cancer types. APOBEC3B was the most aberrantly expressed in most cancer types. In LUAD, we observed a significantly positive correlation of AMES with intratumor heterogeneity (ITH), tumor neoantigen burden (TNB), and tumor mutation burden (TMB). High AMES group had high mutation counts of DNA damage repair pathways, and high enrichment of cell cycle and DNA repair pathways. We identified four prognostic genes (LYPD3, ANLN, MUC5B, and FOSL1) based on AMES, and constructed an AMES-related gene signature. The expressions of four genes were enhanced and accelerated the invasion ability and viability of lung cancer cells. Furthermore, we found that high group increased oxidative stress level.

Conclusions

APOBEC family was associated with genomic instability, DNA damage-related pathways, and cell cycle in LUAD. The AMES-related gene signature had a great potential to indicate the prognosis and guide immunotherapy/chemotherapy for patients suffering from LUAD.

Treated chronic hepatitis B is a good prognostic factor of diffuse large B-cell lymphoma

BACKGROUND/AIMS

Chronic hepatitis B (CHB) is a risk factor for non-Hodgkin lymphoma (NHL). Our recent study suggested that antiviral treatment may reduce the incidence of NHL in CHB patients. This study compared the prognoses of hepatitis B virus (HBV)-associated diffuse large B-cell lymphoma (DLBCL) patients receiving antiviral treatment and HBV-unassociated DLBCL patients.

METHODS

This study comprised 928 DLBCL patients who were treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) at two referral centers in Korea. All patients with CHB received antiviral treatment. Time-to-progression (TTP) and overall survival (OS) were the primary and secondary endpoints, respectively.

RESULTS

Among the 928 patients in this study, 82 were hepatitis B surface antigen (HBsAg)-positive (the CHB group) and 846 were HBsAg-negative (the non-CHB group). The median follow-up time was 50.5 months (interquartile range [IQR]=25.6-69.7 months). Multivariable analyses showed longer TTP in the CHB group than the non-CHB group both before inverse probability of treatment weighting (IPTW; adjusted hazard ratio [aHR]=0.49, 95% confidence interval [CI]=0.29-0.82, p=0.007) and after IPTW (aHR=0.42, 95% CI=0.26-0.70, p<0.001). The CHB group also had a longer OS than the non-CHB group both before IPTW (HR=0.55, 95% CI=0.33-0.92, log-rank p=0.02) and after IPTW (HR=0.53, 95% CI=0.32-0.99, log-rank p=0.02). Although liver-related deaths did not occur in the non-CHB group, two deaths occurred in the CHB group due to hepatocellular carcinoma and acute liver failure, respectively.

CONCLUSION

Our findings indicate that HBV-associated DLBCL patients receiving antiviral treatment have significantly longer TTP and OS after R-CHOP treatment than HBV-unassociated DLBCL patients.

Comparison on different traditional Chinese medicine therapies for chronic hepatitis B liver fibrosis

Background and Aims: Although different kinds of traditional Chinese medicines could reportedly improve the efficacy of antiviral therapy on liver fibrosis caused by HBV, the problem of clinicians on how to choose the appropriate treatment strategies for the patients fails to be solved. This study aims at comparing and ranking different traditional Chinese medicine (TCM) therapies in the treatment of liver fibrosis due to chronic hepatitis B (CHB).

Methods: Eight electronic databases were searched from their establishment to 17 Aug 2021. All included data and pooled odds ratio were used for network meta-analysis (NMA) and statistical analysis. The consistency was evaluated by the node-splitting analysis. The stability of results and source of heterogeneity were tested by sensitivity analysis. Different treatment strategies (regimens) in this network meta-analysis were ranked with the aid of surface under the cumulative ranking curve (SUCRA) probability value.

Results: A total of 29 articles with 3,106 sufferers were recruited in this NMA. Results of SUCRA value rankings indicated that Fuzheng Huayu therapy or combined with entecavir had preferable effects in improving the clinical efficacy, recovering the level of hyaluronic acid, IV-C, ALT, ALB, and TBil, relieving the TCM symptoms including hypochondriac pain and poor appetite, regaining the width of portal vein and thickness of spleen, and lessening side effects. Apart from these, Ziyin Shugan therapy or combined with ETV could also be suitable to regain the level of laminin, PC-III, and AST, relieve fatigue and HBV-DNA conversion.

Conclusion: This NMA confirmed the efficacy and safety of different treatment therapies for improving CHB liver fibrosis, including the serum biomarkers of live fibrosis and serum parameters for liver function, TCM symptoms, imaging indexes, HBV-DNA conversion rate, which offered the TCM practitioners crucial reference value on clinical medication.

Role of hepatitis B virus in development of hepatocellular carcinoma: Focus on covalently closed circular DNA

Chronic infection with hepatitis B virus (HBV) remains a major global health problem, especially in developing countries. It may lead to prolonged liver damage, fibrosis, cirrhosis, and hepatocellular carcinoma. Persistent chronic HBV infection is related to host immune response and the stability of the covalently closed circular DNA (cccDNA) in human hepatocytes. In addition to being essential for viral transcription and replication, cccDNA is also suspected to play a role in persistent HBV infections or hepatitis relapses since cccDNA is very stable in non-dividing human hepatocytes. Understanding the pathogenicity and oncogenicity of HBV components would be essential in the development of new diagnostic tools and treatment strategies. This review summarizes the role and molecular mechanisms of HBV cccDNA in hepatocyte transformation and hepatocarcinogenesis and current efforts to its detection and targeting.

Research progress in hepatitis B virus covalently closed circular DNA

Hepatitis B virus (HBV) infections are a global public health issue. HBV covalently closed circular DNA (cccDNA), the template for the transcription of viral RNAs, is a key factor in the HBV replication cycle. Notably, many host factors involved in HBV cccDNA epigenetic modulation promote the development of hepatocellular carcinoma (HCC). The HBV cccDNA minichromosome is a clinical obstacle that cannot be efficiently eliminated. In this review, we provide an update on the advances in research on HBV cccDNA and further discuss factors affecting the modulation of HBV cccDNA. Hepatitis B virus X protein (HBx) contributes to HBV cccDNA transcription and the development of hepatocarcinogenesis through modulating host epigenetic regulatory factors, thus linking the cccDNA to hepatocarcinogenesis. The measurable serological biomarkers of continued transcription of cccDNA, the effects of anti-HBV drugs on cccDNA, and potential therapeutic strategies targeting cccDNA are discussed in detail. Thus, this review describes new insights into HBV cccDNA mechanisms and therapeutic strategies for cleaning cccDNA, which will benefit patients with liver diseases.

Roles of APOBEC3 in hepatitis B virus (HBV) infection and hepatocarcinogenesis

APOBEC3 (A3) cytidine deaminases inhibit hepatitis B virus (HBV) infection and play vital roles in maintaining a variety of biochemical processes, including the regulation of protein expression and innate immunity. Emerging evidence indicates that the deaminated deoxycytidine biochemical activity of A3 proteins in single-stranded DNA makes them a double-edged sword. These enzymes can cause cellular genetic mutations at replication forks or within transcription bubbles, depending on the physiological state of the cell and the phase of the cell cycle. Under pathological conditions, aberrant expression of A3 genes with improper deaminase activity regulation may threaten genomic stability and eventually lead to cancer development. This review attempted to summarize the antiviral activities and underlying mechanisms of A3 editing enzymes in HBV infections. Moreover, the correlations between A3 genes and hepatocarcinogenesis were also elucidated.

Quantification of intrahepatic cccDNA in HBV associated hepatocellular carcinoma by improved ddPCR method

The quantification of intrahepatic covalently closed circular DNA (cccDNA) is important for assessing the efficiency of anti-HBV therapy. Exonuclease treatment is essential before real-time quantitative PCR (qPCR) or droplet digital PCR (ddPCR) measurement to improve the specificity of cccDNA quantification. In this research, we compared the limit of detection (LOD) of qPCR and ddPCR and evaluated the digestion efficiency of three exonuclease treatments, PSAD, exonuclease III and T5 exonuclease, when measuring cccDNA in cells or clinical samples by ddPCR. We demonstrated that the LOD of ddCPR was 5.9 copies/reaction, which was much lower than that of qPCR (54.9 copies/reaction), indicating that ddPCR is more sensitive than qPCR. Meanwhile, compared to PSAD or Exo III, UNG and T5 exonuclease treatment combined with ddPCR is more effective in detecting intrahepatic cccDNA in clinical samples. Finally, the median intrahepatic cccDNA was 2.6 copies/10⁴ cells in 26 pairs of HCC samples determined by the improved ddPCR method. Therefore, we developed an optimized ddPCR method, which can be used for the absolute quantification of low levels of intrahepatic cccDNA more precisely.

The Hepatitis B Virus Interactome: A Comprehensive Overview

Despite the availability of a prophylactic vaccine, chronic hepatitis B (CHB) caused by the hepatitis B virus (HBV) is a major health problem affecting an estimated 292 million people globally. Current therapeutic goals are to achieve functional cure characterized by HBsAg seroclearance and the absence of HBV-DNA after treatment cessation. However, at present, functional cure is thought to be complicated due to the presence of covalently closed circular DNA (cccDNA) and integrated HBV-DNA. Even if the episomal cccDNA is silenced or eliminated, it remains unclear how important the high level of HBsAg that is expressed from integrated HBV DNA is for the pathology. To identify therapies that could bring about high rates of functional cure, in-depth knowledge of the virus' biology is imperative to pinpoint mechanisms for novel therapeutic targets. The viral proteins and the episomal cccDNA are considered integral for the control and maintenance of the HBV life cycle and through direct interaction with the host proteome they help create the most optimal environment for the virus whilst avoiding immune detection. New HBV-host protein interactions are continuously being identified. Unfortunately, a compendium of the most recent information is lacking and an interactome is unavailable. This article provides a comprehensive review of the virus-host relationship from viral entry to release, as well as an interactome of cccDNA, HBc, and HBx.

Residual HBV DNA and pgRNA viraemia is associated with hepatocellular carcinoma in chronic hepatitis B patients on antiviral therapy

BACKGROUND

We aimed to assess whether residual hepatitis B virus (HBV) viraemia is associated with HCC development.

METHODS

This is a case-control study of 104 patients [52 HCC and 52 non-HCC (matched with age, gender, cirrhosis and treatment duration)] on ≥ 3 years entecavir (ETV) with unquantifiable HBV DNA by Cobas Taqman assay v2.0 (Roche Diagnostics; lower limit of quantification [LLOQ] 20 IU/mL). Serial sera within 1, 1-2, and > 2 years prior to HCC diagnosis or last follow-up (LFU) were measured for HBV DNA and pre-genomic (pg) RNA using a highly sensitive semi-quantitative PCR assay with lower limit of detection of 10 IU/mL and LLOQ of 51.5 IU/mL, respectively.

RESULTS

Among the 104 patients (80.8% male, median age 61.2 years old, 38.5% cirrhosis, median duration of ETV 45.5 months), 38.5% and 9.6% HCC patients had undetectable serum DNA and pgRNA, respectively, compared to 65.4% and 36.5% in non-HCC patients; P = 0.005 & 0.001, respectively, at the time of HCC diagnosis/LFU. Detectable HBV DNA and pgRNA were associated with a higher 2-year risk of HCC development (HR 2.79, 95% CI 1.424-5.468 & HR 4.544, 95% CI 1.07-19.289, respectively). No significant differences were observed for qHBsAg levels between HCC and non-HCC patients.

CONCLUSIONS

More than 50% CHB patients on ETV with HBV DNA < LLOQ by standard assay had persistent viraemia as determined by a more sensitive assay. Detectable HBV DNA or pgRNA by more sensitive assays was associated with HCC development. More potent viral suppression is required to further reduce the risk of HCC.

Recent Advances in Hepatitis B Treatment

Hepatitis B virus infection affects over 250 million chronic carriers, causing more than 800,000 deaths annually, although a safe and effective vaccine is available. Currently used antiviral agents, pegylated interferon and nucleos(t)ide analogues, have major drawbacks and fail to completely eradicate the virus from infected cells. Thus, achieving a "functional cure" of the infection remains a real challenge. Recent findings concerning the viral replication cycle have led to development of novel therapeutic approaches including viral entry inhibitors, epigenetic control of cccDNA, immune modulators, RNA interference techniques, ribonuclease H inhibitors, and capsid assembly modulators. Promising preclinical results have been obtained, and the leading molecules under development have entered clinical evaluation. This review summarizes the key steps of the HBV life cycle, examines the currently approved anti-HBV drugs, and analyzes novel HBV treatment regimens.

Clinical Efficacy and Safety of Eight Traditional Chinese Medicine Combined with Entecavir in the Treatment of Chronic Hepatitis B Liver Fibrosis in Adults: A Network Meta-Analysis

BACKGROUND

Traditional Chinese medicine (TCM) is used as an adjuvant drug for the treatment of chronic hepatitis B liver fibrosis and is used frequently. We still do not know which TCM has the best curative effect as an adjuvant drug. Therefore, we decided to use network meta-analysis to solve this problem.

METHODS

We used the RevMan software (5.3) and Stata software (13.0) to achieve this network meta-analysis (NMA). The primary outcomes of this study were HA, LN, PCIII, and IV-C; the secondary outcomes of this study were AST, ALT, and HBV-DNA negative conversion rate, and the Cochrane risk-of-bias tool was used to assess the quality of the included studies. For all outcomes, the scissors funnel plot, Egger test, and Begg test were used to detect publication bias, and sensitivity analysis was used to investigate the stability of the results. And the meta-regression was used to explore the source of heterogeneity.

RESULTS

A total of 34 articles were included in this study. The study involved a total of 3199 patients, of which 1578 were assigned to the control group and 1621 patients were assigned to the experimental group. The number of men and women is roughly equal, and the average age is about 43 years old. In addition, nine treatment strategies were involved in this study. The combination of TCM and entecavir can significantly improve the patients' HA, LN, PCIII, IV-C, AST, ALT, and HBV-DNA negative conversion rates. The comprehensive evaluation results showed that FHC combined with entecavir has more advantages than other treatment strategies.

CONCLUSION

For improving the HBV-DNA negative conversion rates, adding TCM to the therapeutic strategies does not seem to show absolute superiority. Finally, FHC combined with entecavir is the best therapeutic strategy.

DHX9 interacts with APOBEC3B and attenuates the anti-HBV effect of APOBEC3B

Hepatitis B virus (HBV) is a partially double-stranded DNA virus that replicates by reverse transcription. We previously demonstrated that the host restriction factor-APOBEC3B (A3B) inhibited HBV replication which was dependent on its deaminase activity during reverse transcription. However, the host factors involved in the process of regulating the anti-HBV function of A3B are less known. In this research, to obtain a comprehensive understanding of the interaction networks of A3B, we conducted coimmunoprecipitation and mass spectrometry to identify A3B-interacting proteins in the presence of HBV. By this approach, we determined that DExD/H-box helicase 9 (DHX9) suppressed the anti-HBV effect of A3B, and this suppression was dependent on their interaction. Although DHX9 did not affect the deamination activity of A3B in vitro assay or the viral DNA editing of A3B in HepG2-NTCP cells that support HBV infection, it inhibited the binding of A3B with pgRNA. These data suggest that DHX9 can interact with A3B and attenuate the anti-HBV efficacy of A3B.

Abbreviations: 3D-PCR: differential DNA denaturation PCR; APOBEC3: apolipoprotein B mRNA-editing catalytic polypeptide 3; cccDNA: covalently closed circular DNA; co-IP: coimmunoprecipitation; DDX: DExD-box RNA helicases; HBc: HBV core protein; HBV: hepatitis B virus; HepAD38: HepG2 cell line stably transfected with HBV DNA; HepG2-NTCP: HepG2 cell line stably transfected with Na+/taurocholate cotransporter polypeptide; Huh7: human hepatoma cell line; pgRNA: pregenomic RNA; PPI: protein–protein interactions; RC DNA: relaxed circular DNA.

Targeting Hepatitis B Virus Covalently Closed Circular DNA and Hepatitis B Virus X Protein: Recent Advances and New Approaches

Chronic Hepatitis B virus (HBV) infection remains a worldwide concern and public health problem. Two key aspects of the HBV life cycle are essential for viral replication and thus the development of chronic infections: the establishment of the viral minichromosome, covalently closed circular (ccc) DNA, within the nucleus of infected hepatocytes and the expression of the regulatory Hepatitis B virus X protein (HBx). Interestingly, nuclear HBx redirects host epigenetic machinery to activate cccDNA transcription. In this Perspective, we provide an overview of recent advances in understanding the regulation of cccDNA and the mechanistic and functional roles of HBx. We also describe the progress toward targeting both cccDNA and HBx for therapeutic purposes. Finally, we outline standing questions in the field and propose complementary chemical biology approaches to address them.

lncRNA-PDPK2P promotes hepatocellular carcinoma progression through the PDK1/AKT/Caspase 3 pathway

Hepatocellular carcinoma (HCC) is a malignancy with one of the worst prognoses. Long noncoding RNA (lncRNA) are emerging as an important regulator of gene expression and function, leading to the development of cancer. The aim of this study was to determine the relationship between lncRNA and HCC and to further guide clinical therapy. lncRNA in HCC and adjacent tissues were screened, and the correlation between lncRNA-PDPK2P expression in liver tissues and the pathological characteristics and severity of HCC was assessed. The effects of PDPK2P on HCC proliferation, apoptosis, metastasis, and invasion were also systematically investigated via CCK-8 assay, flow cytometry, scratch wound healing, and transwell assay, respectively. The relationship between PDPK2P and PDK1 was verified by RNA pull-down, rescue experiments and western blot. lncRNA-PDPK2P was highly expressed in HCC tissues with a distinct positive correlation between PDPK2P and PDK1, and the upregulation was clinically associated with a larger tumor embolus, low differentiation, and poor survival. Mechanistically, lncRNA-PDPK2P interacted with PDK1 and promoted HCC progression through the PDK1/AKT/caspase 3 signaling pathway. lncRNA-PDPK2P can promote HCC progression, suggesting it may be a clinically valuable biomarker and serve as a molecular target for the diagnosis, prognosis, and therapy of hepatocellular carcinoma.

Reduced HBV cccDNA and HBsAg in HBV-associated hepatocellular carcinoma tissues

Approximately 50% of hepatocellular carcinoma (HCC) is attributable to chronic infection with hepatitis B virus (HBV). Serum hepatitis B surface antigen (HBsAg) is an important diagnostic marker of HBV infection, whereas intrahepatic HBV covalently closed circular DNA (cccDNA) is a surrogate marker of HBV persistence. This study aimed to investigate relationships between serum HBsAg, intrahepatic HBsAg, and intrahepatic cccDNA in HBV-associated HCC. Intrahepatic HBsAg was determined by immunohistochemistry in matched non-cancerous and HCC tissues from 88 patients; 56 patients (63.64%) were serum HBsAg positive. In serum HBsAg-positive group, intrahepatic HBsAg was positive staining in 73.2% of non-cancerous tissues, but only in 10.7% of HCC tissues. Significant correlation between serum HBsAg and intrahepatic HBsAg was observed in non-cancerous tissues (p < 0.001), but not in HCC tissues (p = 0.415). Absolute quantification of intrahepatic cccDNA was performed by droplet digital PCR in tissues from 30 patients; 18 patients (60%) were serum HBsAg positive. In serum HBsAg-positive group, intrahepatic cccDNA was detected in 66.66% of non-cancerous tissues, but only in 5.55% of HCC tissue; intrahepatic cccDNA levels in non-cancerous tissues were significantly higher than those in HCC tissues (p < 0.001), and correlated with serum HBsAg (p < 0.01). Significant correlations between intrahepatic HBsAg and intrahepatic cccDNA were found in both non-cancerous tissues (p < 0.01) and HCC tissues (p < 0.05). We concluded that HBV cccDNA and intrahepatic HBsAg in HBV-associated HCC tissues were significantly reduced, as compared with matched non-cancerous tissues. This warrants further investigation into the impacts and the cause(s) of cccDNA reduction in HBV-associated HCC tissues, which might yield novel immune-related therapy for HBV-associated HCC.

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

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

Fuzheng Huayu capsule as an adjuvant treatment for HBV-related cirrhosis: A systematic review and meta-analysis

Fuzheng Huayu (FZHY) capsule, a formulated traditional Chinese medicine product with 6 Chinese herbs, is widely used for HBV-related cirrhosis as an adjuvant treatment. However, the efficacy of FZHY capsule for HBV-induced cirrhosis did not be comprehensively proved by systematic analysis. Our current analysis was aimed to assess the efficacy and safety of FZHY capsule by an evidence-based method. Databases, including China National Knowledge Infrastructure, Wangfang, VIP medicine information system, Pubmed, Embase, and Cochrane Library, were searched, and the randomized controlled trials of FZHY capsule were used for the treatment of HBV-associated liver cirrhosis. Meta-analysis was performed by Review Manager 5.3. The efficacy rate, alanine transaminase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), albumin (ALB), Procollagen III protein (PIIIP), hyaluronic acid (HA), laminin (LN), Collagen C Type IV (IV-C), Child-Pugh score, portal vein diameter, spleen thickness, HBeAg negative conversion rate, and HBV-DNA negative conversion rate were systematically assessed. The Cochrane Risk of Bias tool was used to evaluate the methodological quality of eligible studies. Nineteen studies with 1,769 patients were included in the meta-analysis. Compared to conventional treatment, FZHY capsule was effective by increasing the efficacy. FZHY capsule was more efficient in improving ALT, AST, TBIL, PIIIP, HA, LN, IV-C, Child-Pugh grading score, portal vein diameter, spleen thickness, and HBV-DNA negative conversion rate with no serious adverse reactions. Nevertheless, a variety of well-designed randomized controlled trials are needed to confirm these findings since small samples were applied in the previous studies.

Correlation of gene expression and associated mutation profiles of APOBEC3A, APOBEC3B, REV1, UNG, and FHIT with chemosensitivity of cancer cell lines to drug treatment

BACKGROUND

The APOBEC gene family of cytidine deaminases plays important roles in DNA repair and mRNA editing. In many cancers, APOBEC3B increases the mutation load, generating clusters of closely spaced, single-strand-specific DNA substitutions with a characteristic hypermutation signature. Some studies also suggested a possible involvement of APOBEC3A, REV1, UNG, and FHIT in molecular processes affecting APOBEC mutagenesis. It is important to understand how mutagenic processes linked to the activity of these genes may affect sensitivity of cancer cells to treatment.

RESULTS

We used information from the Cancer Cell Line Encyclopedia and the Genomics of Drug Sensitivity in Cancer resources to examine associations of the prevalence of APOBEC-like motifs and mutational loads with expression of APOBEC3A, APOBEC3B, REV1, UNG, and FHIT and with cell line chemosensitivity to 255 antitumor drugs. Among the five genes, APOBEC3B expression levels were bimodally distributed, whereas expression of APOBEC3A, REV1, UNG, and FHIT was unimodally distributed. The majority of the cell lines had low levels of APOBEC3A expression. The strongest correlations of gene expression levels with mutational loads or with measures of prevalence of APOBEC-like motif counts and kataegis clusters were observed for REV1, UNG, and APOBEC3A. Sensitivity or resistance of cell lines to JQ1, palbociclib, bicalutamide, 17-AAG, TAE684, MEK inhibitors refametinib, PD-0325901, and trametinib and a number of other agents was correlated with candidate gene expression levels or with abundance of APOBEC-like motif clusters in specific cancers or across cancer types.

CONCLUSIONS

We observed correlations of expression levels of the five candidate genes in cell line models with sensitivity to cancer drug treatment. We also noted suggestive correlations between measures of abundance of APOBEC-like sequence motifs with drug sensitivity in small samples of cell lines from individual cancer categories, which require further validation in larger datasets. Molecular mechanisms underlying the links between the activities of the products of each of the five genes, the resulting mutagenic processes, and sensitivity to each category of antitumor agents require further investigation.

Recent advances in the study of hepatitis B virus covalently closed circular DNA

Chronic hepatitis B infection is caused by hepatitis B virus (HBV) and a total cure is yet to be achieved. The viral covalently closed circular DNA (cccDNA) is the key to establish a persistent infection within hepatocytes. Current antiviral strategies have no effect on the pre-existing cccDNA reservoir. Therefore, the study of the molecular mechanism of cccDNA formation is becoming a major focus of HBV research. This review summarizes the current advances in cccDNA molecular biology and the latest studies on the elimination or inactivation of cccDNA, including three major areas: (1) epigenetic regulation of cccDNA by HBV X protein, (2) immune-mediated degradation, and (3) genome-editing nucleases. All these aspects provide clues on how to finally attain a cure for chronic hepatitis B infection.

APOBEC3B edits HBV DNA and inhibits HBV replication during reverse transcription

Hepatitis B virus is a partially double-stranded DNA virus that replicates by reverse transcription, which occurs within viral core particles in the cytoplasm. The cytidine deaminase APOBEC3B is a cellular restriction factor for HBV. Recently, it was reported that APOBEC3B can edit HBV cccDNA in the nucleus, causing its degradation. However, whether and how it can edit HBV core-associated DNAs during reverse transcription is unclear. Our studies to address this question revealed the following: First, silencing endogenous APOBEC3B in an HBV infection system lead to upregulation of HBV replication. Second, APOBEC3B can inhibit replication of HBV isolates from genotypes (gt) A, B, C, and D as determined by employing transfection of plasmids expressing isolates from four different HBV genotypes. For HBV inhibition, APOBEC3B-mediated inhibition of replication primarily depends on the C-terminal active site of APOBEC3B. In addition, employing the HBV RNaseH-deficient D702A mutant and a polymerase-deficient YMHA mutant, we demonstrated that APOBEC3B can edit both the HBV minus- and plus-strand DNAs, but not the pregenomic RNA in core particles. Furthermore, we found by co-immunoprecipitation assays that APOBEC3B can interact with HBV core protein in an RNA-dependent manner. Our results provide evidence that APOBEC3B can interact with HBV core protein and edit HBV DNAs during reverse transcription. These data suggest that APOBEC3B exerts multifaceted antiviral effects against HBV.

Immune Evasion Strategies during Chronic Hepatitis B and C Virus Infection

Both hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are a major global healthcare problem with more than 240 million and 70 million infected, respectively. Both viruses persist within the liver and result in progressive liver disease, resulting in liver fibrosis, cirrhosis and hepatocellular carcinoma. Strikingly, this pathogenesis is largely driven by immune responses, unable to clear an established infection, rather than by the viral pathogens themselves. Even though disease progression is very similar in both infections, HBV and HCV have evolved distinct mechanisms, by which they ensure persistence within the host. Whereas HCV utilizes a cloak-and-dagger approach, disguising itself as a lipid-like particle and immediately crippling essential pattern-recognition pathways, HBV has long been considered a "stealth" virus, due to the complete absence of innate immune responses during infection. Recent developments and access to improved model systems, however, revealed that even though it is among the smallest human-tropic viruses, HBV may, in addition to evading host responses, employ subtle immune evasion mechanisms directed at ensuring viral persistence in the absence of host responses. In this review, we compare the different strategies of both viruses to ensure viral persistence by actively interfering with viral recognition and innate immune responses.

Observation of the effect of targeted therapy of 64-slice spiral CT combined with cryoablation for liver cancer

AIM

To observe the effect of targeted therapy with 64-slice spiral computed tomography (CT) combined with cryoablation for liver cancer.

METHODS

A total of 124 patients (142 tumors) were enrolled into this study. According to the use of dual-slice spiral CT or 64-slice spiral CT as a guide technology, patients were divided into two groups: dual-slice group (n = 56, 65 tumors) and 64-slice group (n = 8, 77 tumors). All patients were accepted and received targeted therapy by an argon-helium superconducting surgery system. The guided scan times of the two groups was recorded and compared. In the two groups, the lesion ice coverage in diameter of ≥ 3 cm and < 3 cm were recorded, and freezing effective rate was compared. Hepatic perfusion values [hepatic artery perfusion (HAP), portal vein perfusion (PVP), and the hepatic arterial perfusion index (HAPI)] of tumor tissues, adjacent tissues and normal liver tissues at preoperative and postoperative four weeks in the two groups were compared. Local tumor changes were recorded and efficiency was compared at four weeks post-operation. Adverse events were recorded and compared between the two groups, including fever, pain, frostbite, nausea, vomiting, pleural effusion and abdominal bleeding.

RESULTS

Guided scan times in the dual-slice group was longer than that in the 64-slice group (t = 11.445, P = 0.000). The freezing effective rate for tumors < 3 cm in diameter in the dual-slice group (81.58%) was lower than that in the 64-slice group (92.86%) (χ² = 5.707, P = 0.017). The HAP and HAPI of tumor tissues were lower at four weeks post-treatment than at pre-treatment in both groups (all P < 0.05), and those in the 64-slice group were lower than that in the dual-slice group (all P < 0.05). HAP and PVP were lower and HAPI was higher in tumor adjacent tissues at post-treatment than at pre-treatment (all P < 0.05). Furthermore, the treatment effect and therapeutic efficacy in the dual-slice group were lower than the 64-slice group at four weeks post-treatment (all P < 0.05). Moreover, pleural effusion and intraperitoneal hemorrhage occurred in patients in the dual-slice group, while no complications occurred in the 64-slice group (all P < 0.05).

CONCLUSION

64-slice spiral CT applied with cryoablation in targeted therapy for liver cancer can achieve a safe and effective freezing treatment, so it is worth being used.

APOBEC3B, a molecular driver of mutagenesis in human cancers

Human cancers results in large part from the accumulation of multiple mutations. The progression of premalignant cells is an evolutionary process in which mutations provide the fundamental driving force for genetic diversity. The increased mutation rate in premalignant cells allows selection for increased proliferation and survival and ultimately leads to invasion, metastasis, recurrence, and therapeutic resistance. Therefore, it is important to understand the molecular determinants of the mutational processes. Recent genome-wide sequencing data showed that apolipoprotein B mRNA editing catalytic polypeptide-like 3B (APOBEC3B) is a key molecular driver inducing mutations in multiple human cancers. APOBEC3B, a DNA cytosine deaminase, is overexpressed in a wide spectrum of human cancers. Its overexpression and aberrant activation lead to unexpected clusters of mutations in the majority of cancers. This phenomenon of clustered mutations, termed kataegis (from the Greek word for showers), forms unique mutation signatures. In this review, we will discuss the biological function of APOBEC3B, its tumorigenic role in promoting mutational processes in cancer development and the clinical potential to develop novel therapeutics by targeting APOBEC3B.