Abstract
BackgroundThe risk of hepatocellular carcinoma (HCC) increases in chronic hepatitis B surface antigen (HBsAg) carriers who often have concomitant increase in the levels of benzo[alpha]pyrene-7,8-diol-9,10-epoxide(±) (BPDE)-DNA adduct in liver tissues, suggesting a possible co-carcinogenesis of Hepatitis B virus (HBV) and benzo[alpha]pyrene in HCC; however the exact mechanisms involved are unclear.MethodsThe interaction between hepatitis B spliced protein (HBSP) and microsomal epoxide hydrolase (mEH) was confirmed using GST pull-down, co-immunoprecipitation and mammalian two-hybrid assay; the effects of HBSP on mEH-mediated B[alpha]P metabolism was examined by high performance liquid chromatography (HPLC); and the influences of HBSP on B[alpha]P carcinogenicity were evaluated by bromodeoxyuridine cell proliferation, anchorage-independent growth and tumor xenograft.ResultsHBSP could interact with mEH in vitro and in vivo, and this interaction was mediated by the N terminal 47 amino acid residues of HBSP. HBSP could greatly enhance the hydrolysis activity of mEH in cell-free mouse liver microsomes, thus accelerating the metabolism of benzo[alpha]pyrene to produce more ultimate carcinnogen, BPDE, and this effect of HBSP requires the intact HBSP molecule. Expression of HBSP significantly increased the formation of BPDE-DNA adduct in benzo[alpha]pyrene-treated Huh-7 hepatoma cells, and this enhancement was blocked by knockdown of mEH. HBSP could enhance the cell proliferation, accelerate the G1/S transition, and promote cell transformation and tumorigenesis of B[alpha]P-treated Huh-7 hepatoma cells.ConclusionsOur results demonstrated that HBSP could promote carcinogenic effects of B[alpha]P by interacting with mEH and enhancing its hydrolysis activity.
Highlights
The risk of hepatocellular carcinoma (HCC) increases in chronic hepatitis B surface antigen (HBsAg) carriers who often have concomitant increase in the levels of benzo[alpha]pyrene-7,8-diol-9,10-epoxide(±) (BPDE)-DNA adduct in liver tissues, suggesting a possible co-carcinogenesis of Hepatitis B virus (HBV) and benzo [alpha]pyrene in HCC; the exact mechanisms involved are unclear
The results demonstrated that GAL4BD-tagged hepatitis B spliced protein (HBSP), HBSP1–47 and HBSP48–111 as well as VP16-tagged mEH353–455 expressed well in transfected Huh-7 hepatoma cells (Figure 1D)
The luciferase activities (Figure 1E) of Huh-7 hepatoma cells cotransfected with pACT-mEH353–455 and pBIND-HBSP or pBIND-HBSP1–47 were significantly higher (~9 fold for pBIND-HBSP and ~12 fold for pBIND-HBSP1–47) as compared to the negative control (P < 0.01), while the luciferase activity for the pBIND-HBSP48–111 group was similar to negative control
Summary
The risk of hepatocellular carcinoma (HCC) increases in chronic hepatitis B surface antigen (HBsAg) carriers who often have concomitant increase in the levels of benzo[alpha]pyrene-7,8-diol-9,10-epoxide(±) (BPDE)-DNA adduct in liver tissues, suggesting a possible co-carcinogenesis of Hepatitis B virus (HBV) and benzo [alpha]pyrene in HCC; the exact mechanisms involved are unclear. In addition to the immune response to the viral proteins, which is considered to play a major role in the liver disease outcome, some HBV proteins directly participate in chronic hepatitis and HCC, among which transcription activators of X protein (HBx) [6,7] and truncated middle surface protein (MHBst) have been extensively studied [8]. Epidemicological studies have shown that the risk for developing HCC increased dramatically in those with the combination of higher BPDE-DNA adducts and HBV infection [3,4], suggesting the possible role of HBV-B[alpha]P interaction in hepatocarcinogenesis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
