Anticancer activity evaluation of the Solanum glycoalkaloid solamargine - Triggering apoptosis in human hepatoma cells

Solamargine, an herbal and molluscicidal medicine derived from Solanum inca num, is a steroidal alkaloid glycoside. To characterize the anticancer mech anism of solamargine on human hepatoma cells (Hep3B), changes of eel morpho logy, DNA content, and gene expression of cells after solamargine treatment were studied. The appearance in solamargine-treated cells of chromatin con densation, DNA fragmentation, and a sub-G, peak in a DNA histogram suggests that solamargine induces cell death by apoptosis. The maximum number of de ad Hep3B cells was detected within 2 hr of incubation with constant concent rations of solamargine, and no further cell death was observed after an ext ended incubation with solamargine, indicating that the action of solamargin e was irreversible. To determine the susceptibility of cell phases to solam argine-mediated apoptosis, Hep3B cells were synchronized at defined cell cy cles by cyclosporin A, colchicine, and genistein, followed by solamargine t reatment. The IC50 values of solamargine for control, G(0)/G(1)-, M-, and G (2)/M-synchronized Hep3B cells were 5.0, > 10, 3.7, and 3.1 mug/mL, implyin g that cells in the G(2)/M phases are relatively susceptible to solamargine mediated apoptosis. In addition, a parallel up-regulation of tumor necrosi s factor receptor (TNFR)-I and -II on Hep3B cells was detected after solama rgine treatment, and the solamargine-mediated cytotoxicity could be neutral ized with either TNFR-I or -II specific antibody. Therefore, these results reveal that the actions of TNFR-I and II on Hep3B cells may be independent, and both are involved in the mechanism of solamargine-mediated apoptosis. BIOCHEM PHARMACOL 60;12:1865-1873, 2000. (C) 2000 Elsevier Science Inc.