Temporal treatment with interferon-beta prevents hepatocellular carcinoma in hepatitis B virus X gene transgenic mice

Hepatitis B virus X protein-elevated MSL2 modulates hepatitis B virus covalently closed circular DNA by inducing degradation of APOBEC3B to enhance hepatocarcinogenesis

Chronic hepatitis B virus (HBV) infection is a leading cause in the occurrence of hepatitis B, liver cirrhosis, and liver cancer, in which nuclear HBV covalently closed circular DNA (cccDNA), the genomic form that templates viral transcription and sustains viral persistence, plays crucial roles. In the present study, we explored the hypothesis that HBV X protein (HBx)-elevated male-specific lethal 2 (MSL2) activated HBV replication by modulating cccDNA in hepatoma cells, leading to hepatocarcinogenesis. Immunohistochemical analysis revealed that the expression of MSL2 was positively associated with that of HBV and was increased in the liver tissues of HBV-transgenic mice and clinical HCC patients. Interestingly, microarray profiling identified that MSL2 was associated with those genes responding to the virus. Mechanistically, MSL2 could maintain HBV cccDNA stability through degradation of APOBEC3B by ubiquitylation in hepatoma cells. Above all, HBx accounted for the up-regulation of MSL2 in stably HBx-transfected hepatoma cell lines and liver tissues of HBx-transgenic mice. Luciferase reporter gene assays revealed that the promoter region of MSL2 regulated by HBx was located at nucleotide -1317/-1167 containing FoxA1 binding element. Chromatin immunoprecipitation assay validated that HBx could enhance the binding property of FoxA1 to MSL2 promoter region. HBx up-regulated MSL2 by activating YAP/FoxA1 signaling. Functionally, silencing MSL2 was able to block the growth of hepatoma cells in vitro and in vivo.

CONCLUSION

HBx-elevated MSL2 modulates HBV cccDNA in hepatoma cells to promote hepatocarcinogenesis, forming a positive feedback loop of HBx/MSL2/cccDNA/HBV. Our finding uncovers insights into the mechanism by which MSL2 as a promotion factor in host cells selectively activates extrachromosomal DNA. (Hepatology 2017;66:1413-1429).

Different antiviral effects of IFNα and IFNβ in an HBV mouse model

Interferons α and β (IFNα and IFNβ) are type I interferons produced by the host to control pathogen propagation. However, only a minority of chronic hepatitis B (CHB) patients generate a sustained response after treatment with recombinant IFNα. The anti-HBV effect of IFNβ and the underlying mechanism are not well-understood. Here, we compared the antiviral activities of IFNα and IFNβ by application of IFNα or IFNβ expression plasmids using the well-established HBV hydrodynamic injection (HI) mouse model. Injection of IFNα expression plasmid could significantly reduce HBV serum markers including HBsAg, HBeAg and HBV DNA as well as the number of HBcAg positive cells in the liver, while IFNβ showed only a weak inhibition of HBV replication. In contrast to IFNβ, IFNα resulted in elevated expression levels of IFN stimulated genes (ISGs) as well as the proinflammatory cytokine interleukin 6 (IL6) in the liver. Moreover, IFNβ treated mice showed higher expression levels of the anti-inflammatory cytokines IL10 and TGFβ in the liver compared to IFNα. Our results demonstrated that both IFNα and IFNβ exert antiviral activities against HBV in HI mouse model, but IFNα is more effective than IFNβ.

Contributions of transgenic mouse studies on the research of hepatitis B virus and hepatitis C virus-induced hepatocarcinogenesis

Transgenic mouse technology has enabled the investigation of the pathogenic effects, including those on development, immunological reactions and carcinogenesis, of viral genes directly in living organism in a real-time manner. Although viral hepatocarcinogenesis comprises multiple sequences of pathological events, that is, chronic necroinflammation and the subsequent regeneration of hepatocytes that induces the accumulation of genetic alterations and hepatocellular carcinoma (HCC), the direct action of viral proteins also play significant roles. The pathogenesis of hepatitis B virus X and hepatitis C virus (HCV) core genes has been extensively studied by virtue of their functions as a transactivator and a steatosis inducer, respectively. In particular, the mechanism of steatosis in HCV infection and its possible association with HCC has been well studied using HCV core gene transgenic mouse models. Although transgenic mouse models have remarkable advantages, they are intrinsically accompanied by some drawbacks when used to study human diseases. Therefore, the results obtained from transgenic mouse studies should be carefully interpreted in the context of whether or not they are well associated with human pathogenesis.

Adjuvant interferon for early or late recurrence of hepatocellular carcinoma and mortality from hepatocellular carcinoma following curative treatment: A meta-analysis with comparison of different types of hepatitis

Adjuvant interferon (IFN) therapy following curative treatment for hepatocellular carcinoma (HCC) has been extensively investigated; however, the clinical benefits with different hepatitis backgrounds remain unclear. Medline, Embase, PubMed and the Cochrane Library databases were searched to identify randomized trials and cohort studies that enrolled HCC patients who received curative surgery or ablation therapy followed by IFN and control subjects; the studies were required to include data on early or late recurrence and mortality rates of HCC. Hepatitis B virus (HBV) associated with HCC (HBV-HCC) and hepatitis C virus (HCV) associated with HCC (HCV-HCC) were separately analyzed and recurrence, mortality and clinicopathological factors were compared. A total of 14 studies (9 randomized trials and 5 cohort studies, including 1,385 patients in total) were eligible for meta-analysis. IFN was found to decrease mortality and early recurrence rates, but exerted no effect on late recurrence rate. The effect of IFN differed between HBV-HCC and HCV-HCC cases. In HCV-HCC, IFN significantly reduced mortality as well as recurrence rates. However, in HBV-HCC patients, IFN reduced mortality rather than recurrence rates, although it also reduced the recurrence rate in certain subgroups. In conclusion, the effect of adjuvant IFN on postoperative recurrence differed between HBV-HCC and HCV-HCC cases; therefore, different strategies with adjuvant IFN should be used to treat HCC with different hepatitis backgrounds.

Hepatitis B virus X induces cell proliferation in the hepatocarcinogenesis via up-regulation of cytoplasmic p21 expression

BACKGROUND

Hepatitis B virus X protein (HBx) has been shown to induce hepatocarcinogenesis by disrupting the functions of intracellular molecules. Cyclin-dependent kinase inhibitor p21 (Cip1/WAF1), known as a tumour-suppressor gene, has been reported to have paradoxical function, that is, acting as an oncogene, particularly when expressed in the cytoplasm. The effects of HBx on the expression and function of p21 also remain controversial.

AIMS

We attempted to investigate the role of HBx in the hepatocarcinogenic process, focusing on the association with this paradoxical function of p21. The results obtained were further verified with experiments using the antihepatocarcinogenic action of interferon (IFN)-β.

METHODS

HBx transgenic mice (Xg) and HBx-transfected hepatoma cell lines were used. Intracellular localization of p21 was determined by Western blot analysis and immunofluorescence.

RESULTS

Xg and HBx-transfected cells exhibited increased expression of p21. Up-regulation of p21 was positively correlated with the expression of cyclin D1 and inactive phosphorylation of retinoblastoma protein (pRb). These HBx-induced cell proliferative responses were cancelled by knockdown of p21, which resulted in growth reduction in HBx-expressing cells, suggesting the oncogenic properties of HBx-induced p21. HBx induced accumulation of p21 in the cytoplasm, and activation of PKCα was involved. Finally, IFN-β-treated Xg liver, as well as hepatoma cells, showed a shift of cytoplasmic p21 to the nucleus, accompanied by the abrogation of HBx-induced oncogenic modulation.

CONCLUSIONS

Our results suggest that HBx induces hepatocarcinogenesis via PKCα-mediated overexpression of cytoplasmic p21 and IFN-β suppressed these molecular events by shifting p21 to the nucleus.

Impact of hepatitis B virus X protein on the DNA damage response during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is one of the most prevalent and lethal cancers worldwide. The main HCC-associated diseases are chronic infections with hepatitis B virus (HBV) and hepatitis C virus (HCV), and HBV-associated HCC is still prevalent in Asia. Many studies have suggested that HBV X protein (HBX), which is the most common ORF integrated into the host genome, plays a crucial role in hepatocarcinogenesis. However, the accumulated evidence regarding HBX-mediated signaling pathways is not concordant, and it is difficult to understand the mechanistic nature of HBX-associated hepatocarcinogenesis. For example, HBX was reported to inactivate the early responses to DNA damage via p53-dependent and -independent pathways by interacting with several DNA damage-binding proteins and was also reported to sensitize cells to p53-mediated apoptosis via ataxia-telangiectasia and Rad3-related (ATR)-dependent signaling. HBX also interferes with the centrosome replication process, resulting in rearrangement of chromosomes with micronuclei. Moreover, HBX was found to sensitize protein kinases such as Ras/Raf/mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), stress-activated protein kinase/NH2-terminal-Jun kinase (SAPK/JNK), protein kinase B (PKB/Akt), and Janus kinase/STAT (JAK/STAT), indicating that a variety of signaling pathways may be activated by HBX. In this review, we focus on the roles of HBX in DNA damage repair during HCC development, with a view to achieving a better understanding of the significance of HBX in the early steps of hepatocarcinogenesis.

Advance in the mouse model of hepatitis B virus infection

Hepatitis B virus (HBV) infection is a major worldwide healthy problem and now the virus and the virus-caused diseases have been known deeply. However, due to lack of a practical and convenient animal model, the study of HBV biology and the therapeutic development of HBV infection are still at a low level. As a common species used in laboratory, mice are studied most and the genetic and immune system are clearly understood. In this paper, we briefly describes the mouse models currently available in HBV.