INDUCTION OF CELL-CYCLE PROGRESSION BY HEPATITIS-B VIRUS HBX GENE-EXPRESSION IN QUIESCENT MOUSE FIBROBLASTS

The HBx gene of hepatitis B virus has been shown to induce hepatic tum ors in transgenic mice and is implicated in hepatocarcinogenesis in hu man hepatitis B virus infection. To further characterize the role of H Bx gene in carcinogenesis, we established mouse fibroblast cell lines in which the expression of HBx gene could be controlled by glucocortic oid hormone and examined the effect of HBx gene expression on cell gro wth in vitro. Along with the expression of HBx gene, most cells in the G(0)/G(1) phase moved into the S phase in 24 h, and the cell cycle pr ogressed further toward 48 h. Induction of DNA synthesis was also demo nstrated by bromo-deoxyuridine labeling analysis. These results indica te that HBK gene has a function to trigger the synthesis of cellular D NA and suggest that HBx gene mag play a role in hepatocarcinogenesis i n human infection ba driving deregulated cell cycle progression.