[Increased cellular proliferation in BEL-7402 hepatoma cells transfected by human hepatic stimulator substance gene]

A hepatotropic factor originally identified in weanling or regenerating rat livers, known as hepatic stimulator substance (HSS), is characterized by promoting markedly liver regeneration after partial hepatectomy. Although HSS gene and the gene product have been described recently, the cellular mechanism of HSS and its genetic function remain obscure. In our previous studies, human HSS (hHSS) was demonstrated to promote the growth of hepatoma cells and phosphorylate the mitogen-activated protein kinase (MAPK). In this study, we reported the growth features of human hepatoma cells response to hHSS gene transfection. The hHSS eukaryotic vector was transfected to BEL-7402 hepatoma cells and the expression of hHSS was analyzed with Northern and Southern blot. The results showed that the HSS recombinant construct was functionally expressed in the target cells as analyzed with Northern blot and reverse transcriptase polymerase chain reaction (RT-PCR). The growth potential of HSS transfected hepatoma cells was markedly enhanced as compared with the non transfected cells. The S-phase of the hHSS-transfected cells increased by 61.5% than that of the non-transfected cells as shown by flow cytometry. Moreover, MAPK phosphorylation, one of the most important mitogenic indexes of growth signal cascade, was profoundly activated at sites of Thr202/Tyr204 due to HSS gene transfer. Based on these results, it is concluded that the introduction of HSS gene into hepatoma cells might be able to stimulate directly the cellular growth in vitro, allowing a possibility of reevaluation of HSS mechanism in intact cells.