Background: Oxidative stress has been implicated in the pathogenesis of a wide spectrum of human diseases, including Hepatitis B virus (HBV)-related liver disease. Hepatitis B virus X protein (HBx) is a key regulator of HBV that exerts pleiotropic activity on cellular functions. Recent studies showed that HBx alters mitochondrial membrane potential, thereby sensitizing cells to pro-apoptotic signals. However, it remains largely unknown whether susceptibility of hepatocytes could be disturbed by HBx under oxidative stress conditions. The purpose of this study is to determine the apoptotic susceptibility of HBx-expressing hepatocytes upon exposure to pro-oxidant stimuli in vitro and in vivo and explore its underlying mechanism. Results: Although expression of HBx itself did not activate apoptotic signaling, it significantly enhanced oxidative stress-induced cell death both in vitro and in vivo. Interestingly, this phenomenon was associated with a pronounced reduction of protein levels of Mcl-1, but not other anti-apoptotic Bcl-2 members. Importantly, enforced expression of Mcl-1 prevented HBx-triggered cell apoptosis; conversely, specific knockdown of Mcl-1 exacerbated HBx-induced apoptosis upon exposure to oxidative stress. Furthermore, inhibition of caspase-3 not only abrogated HBx-triggered apoptotic killing but also blocked HBx-induced Mcl-1 loss. Additionally, expression of HBx and Mcl-1 was found to be inversely correlated in HBV-related hepatocellular carcinogenesis (HCC) tissues. Conclusions: Our findings indicate that HBx exerts pro-apoptotic effect upon exposure to oxidative stress probably through accelerating the loss of Mcl-1 protein via caspase-3 cascade, which may shed a new light on the molecular mechanism of HBV-related hepatocarcinogenesis.

The impact of antiviral therapy before tumorigenesis on microvascular invasion (MVI) of Chronic hepatitis B (CHB)-related hepatocellular carcinoma (HCC) is still unknown. In this retrospective cohort study 3,276 HCC patients with early-stage who underwent curative resection were included. We investigated the effect of precancer antiviral therapy on the pathology, especially MVI, of CHB-related HCC. MVI occurrence rates of CHB-related HCC stratified by histopathologic inflammation grades of G1, G2, and G3 were 30.4%, 34.7%, and 38.6%, respectively, compared to 19.8% for CHB-negative HCC. Patients who received standard antiviral treatment showed much lower rates of MVI, higher tumor capsule integrity, less frequent satellite micronodules and lower AFP level compared to the no antiviral group. Moreover, precancer antiviral therapy prolonged the disease-free survival (DFS), which are also proved to be independent indicators of DFS. In addition, we show that antivirals may suppress early progression of HCC primarily by inhibition of HBV viral load, and influencing the expression levels of CK18, GPC3, OPN and pERK. Hence, we demonstrate that precancer antivirals significantly reduce the MVI rate of CHB-related HCC, reduce malignancy of early-stage HCC, and improve HCC prognosis. Thus, this study confirms the importance of antiviral therapy for CHB patients.