The Role of N-terminal Truncated Retinoblastoma Protein (pRb94) in Transcriptional Regulation of the Hepatitis B Virus X-protein in Human Hepatoma Cells

ABSTRACT

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer deaths in the world, especially in Korea where 6-12% of the general population show positive for HbsAg. The accumulating studies suggest that the HBV-X protein found in HBV DNA may be the causative factor in the development of a HCC. METHOD: We studied the role of retinoblastoma (Rb) protein in the suppression of the tumorigenicity of a HCC by using cytomegalovirus (CMV) co-transfected HBV-X protein with retinoblastoma protein (pRb) or N-terminal truncated retinoblastoma protein (pRb94) in HepG2 cell lines. RESULTS: First, culturing HepG2 cells with CMV-Rb/liposome or CMV-Rb94/liposome, we observed the suppression of cell growth by using hemocytometric counting of the cells stained by trypan blue and by using a [3H]thymidine incorporation assay. Then, by using a plasmid co-transfected with the chloramphenicol acetyl transferase(CAT) gene, we investigated the role of HBV-X gene in regulating the transcriptional activity in the HepG2 cells under the control of a kB-like sequence of HIV-1 enhancer and the suppression of its activity by pRb and pRb94. CONCLUSIONS: We concluded that both pRb and pRb94 were capable of suppressing cell growth of a HepG2 cell line containing recombinant plasmids coding HBV-X protein. Furthermore, it was demonstrated that the suppression activity of pRb94 was more potent and sustaining than that of pRb. These results suggest that if additional research is performed on the method of gene delivery, gene therapy using pRb94 might be used as a new modality for the treatment of a HCC.