| Research Abstract |
Hepatocellular carcinoma (HCC) is characterized with a hypervascular tumor. Therefore, transcatheter arterial embolization is a major treatment modality for human HCC, but its efficacy is not yet satisfactory. In the present study, the inhibitory effects of a potent endogenous anti-neoangiogenetic factor, angiostatin, on growth and metastatic potentials of HCC were evaluated by means of angiostatin gene transfection into human hepatoma cell lines. Human plasminogen cDNA was isolated from Hep G2 human hepatoma cells, and the fragment corresponding to the kringle domains 1 to 4 was linked to a secretory signal sequence (SS) and preactivation peptide (PA), and cloned into adenovirus vector (AV-S-K1-4). HuH7 and HepG2 human hepatoma cell lines were co-transfected with the angiostatin gene expression plasmid and the neomycinresistance gene plasmid, and the cells were selected by G418 serection for 3 weeks. However, the stable transfectants expressing sufficient levels of angiostatin could not be established. In contrast, when HuH7 and HepG2 cells were infected with AV-S-K1-4, large amounts of angiostatin were expressed in both cell lines. Cell growth in AV-S-K1-4-infected cells was almost similar to that in the parental cells, while, in a double chamber model, AV-S-K1-4-infected cells clearly suppressed cell proliferation of bovine capillary endothelial cells, although apoptosis of the endothelial cells could not be identified. In animal experiments, parental HuH7 cells were inoculated subcutaneously in athymic mice. Two weeks later AV-S-K1-4 or a control adenovirus vector were directly injected into the subcutaneous tumor. Tumor growth in mice injected with AV-S-K1-4 was apparently suppressed, compared with that in mice receiving a vehicle treatment. These results suggest that gene therapy with angiostatin gene transfection into hepatoma cells inhibits tumor growth probably through blocking tumor angiogenesis.
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