Yuehua Huang1,2, Zhanhui Wang3, Bin Zhou3, Hui Li3, Menfeng Liang3, Zhijian Yu3, Jinlin Hou3
1 1Hepatology Unit and Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China;, 2 Department of Infectious Diseases, The First Affiliate Hospital of Guangzhou Medical College, Guangzhou, China, 3 Hepatology Unit and Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China;
Hepatitis B virus (HBV) basic core promoter (BCP) located within HBV X gene (HBx) is suggested to be associated with hepatocellular carcinoma (HCC) development, and cyclin kinase inhibitor p21WAF1/CIP1 plays a crucial role in pathogenesis of malignant tumors. In present study, we investigated p21WAF1/CIP1 expression modulated by HBx depending on BCP and analyzed cell growth progression on carcinogenicity of HBV infected HCC. Detection of p21WAF1/CIP1 expression in hepatic tissues by immunohistochemistry and identification of BCP mutations in serum with PCR and sequencing were performed from 92 chronic HBV infection patients, including 32 cases of HCC, 28 of liver cirrhosis (LC) and 32 of chronic hepatitis B (CH), respectively. Plasmids of pCMV-HBx1 with BCP wild type and pCMV-HBx2 with BCP mutations were constructed. Four cell lines, HepG2, Huh7, Hep3B and NIH3T3 were transfected with pCMV-tag-HBx1, pCMV-tag-HBx2 and empty plasmid pCMV-tag, respectively. p21WAF1/CIP1 expression was examined using western blotting. The effect of BCP on cell cycle progression was determined by flow-cytometric analysis. The positive rates of p21WAF1/CIP1 expression with BCP mutations, which showed as 21.7%, 21.8% and 41.7%, were significantly lower than that of 66.7%, 78.2% and 85.0% without BCP mutations for tissues of HCC, LC and CH, respectively. In HBx transfected cell lines, HBx1 enhanced p21WAF1/CIP1 expression and G0/G1 arrest was apparently demonstrated, while HBx2 strongly repressed p21WAF1/CIP1 expression and stimulated cell cycle at G1 to S checkpoint. These findings reveal that BCP mutations may be involved in carcinogenesis of HBx-mediated HCC by regulation of p21WAF1/CIP1 expression and cell cycle progression.