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.
Carcinoma, Hepatocellular* ; Chloramphenicol ; Clinical Coding ; Cytomegalovirus ; DNA ; Genetic Therapy ; Hep G2 Cells ; Hepatitis B Surface Antigens ; Hepatitis B virus* ; Hepatitis B* ; Hepatitis* ; HIV Enhancer ; Humans* ; Korea ; Plasmids ; Retinoblastoma Protein* ; Retinoblastoma* ; Trypan Blue

BACKGROUNDAlthough DNA vaccine is considered as the next generation of vaccine, most DNA vaccine candidates are still suffering from the relatively weak immunogenicity despite the increased dosage of plasmid DNA administered. In order to enhance the immune responses elicited by a codon-optimized HIV gag DNA vaccine, a modified plasmid vector pDRVI1.0 and a booster immunization with replicating Tiantan vaccinia (RTV) strain expressing the same gene were employed.

METHODSVector pDRVI1.0 was constructed through inserting the 72-bp element from the SV40 enhancer, which was reported promoting nuclear transport of plasmid DNA, to the upstream of cytomegalovirus enhancer/promoter region of the plasmid vector pVR1012. Gene expression levels from expression plasmids based on pDRVI1.0 and pVR1012 were tested. Humoral and cellular immune responses induced by DNA vaccine alone or DNA prime-RTV boost regimen were determined in mice.

RESULTSIt was shown that the 72-bp element significantly enhanced the gene expression level in non-dividing cells. gag-specific humoral and cellular immune responses induced by DNA vaccination were both significantly improved, while the Th1/Th2 balance was not obviously affected by the 72-bp element. RTV boosting further significantly enhanced DNA vaccine-primed antibody and T cell responses in a Th1-biased manner.

CONCLUSIONSThe 72-bp SV40 enhancer element should be included in the DNA vaccine vector and RTV strain is a very efficient live vector for boosting immunization.

AIDS Vaccines ; immunology ; Amino Acid Sequence ; Animals ; Blotting, Western ; CD8-Positive T-Lymphocytes ; immunology ; Enhancer Elements, Genetic ; Female ; Gene Products, gag ; immunology ; HIV Antibodies ; blood ; Immunoglobulin G ; blood ; Mice ; Mice, Inbred BALB C ; Molecular Sequence Data ; Plasmids ; Simian virus 40 ; genetics ; Vaccination ; Vaccines, DNA ; immunology ; Vaccinia ; immunology