HBx-induced reactive oxygen species activates hepatocellular carcinogenesis via dysregulation of PTEN/Akt pathway.
OBJECTIVE
To investigate the role of hepatitis B virus X-protein (HBx)-induced reactive oxygen species (ROS) on liver carcinogenesis in HBx transgenic mice and HepG2-HBx cells.


METHODS
Cell growth rate was analyzed, and through western blotting, mitogenic signaling was observed. Endogenous ROS from wild and HBx transgenic mice and HepG2-Mock and HBx cells were assayed by FACScalibur. Identification of oxidized and reduced phosphatase and tensin homolog (PTEN) was analyzed through N-ethylmaleimide alkylation, nonreducing electrophoresis.


RESULTS
We observed that the cell-proliferation-related phosphoinositide 3-kinase/Akt pathway is activated by HBx in vivo and in vitro. Increased ROS were detected by HBx. Tumor suppressor PTEN, via dephosphorylation of Akt, was oxidized and inactivated by increased ROS. Increased oxidized PTEN activated the mitogenic pathway through over-activated Akt. However, treatment with ROS scavenger N-acetyl cysteine can reverse PTEN to a reduced form. Endogenously produced ROS also stimulated HBx expression.


CONCLUSIONS
HBx induced ROS promoted Akt pathways via oxidized inactive PTEN. HBx and ROS maintained a positive regulatory loop, which aggravated carcinogenesis.
Disease Model Research Laboratory, Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, 52 Oun-dong, Yuseong-gu, Daejeon 305-806, South Korea.
Hye-Lin
HL
Ha
Dae-Yeul
DY
Yu
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005434:Flow Cytometry; D016166:Free Radical Scavengers / Q000494:pharmacology; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins
D000111:Acetylcysteine; D016166:Free Radical Scavengers; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; C494929:PTEN protein, human; C487757:Pten protein, mouse