OBJECTIVETo study the antitumor effect of saponin extracted from Tupistra chinensis Baker (STCB) against mouse sarcoma S-180 cell proliferation in vitro and in vivo and explore the primary mechanism of this effect.

METHODSCytotoxic effect of STCB on S-180 cells in vitro was evaluated by MTT colorimetry, and its effect against in vitro tumor growth was tested in Kunmin mice bearing S-180 implanted tumor. The morphological and ultrastructural changes of S-180 cells after saponin treatment in vitro were examined with light and transmission electron microscope. Flow cytometry was performed to examine the cell cycle and apoptosis of S180 cells treated with different concentrations of STCB with propidium iodide staining.

RESULTSSTCB could markedly inhibit S-180 cell proliferation in vitro with 50% inhibitory concentration of 34.64 microg/ml. STCB given by intragastric administration also significantly inhibited the growth of S-180 solid tumor, and the inhibition rate exceeded 30% at the dose of 0.5 g/kg, reaching 54.86% at 2 g/kg. Electron microscopy and flow cytometry revealed increased S180 tumor cell apoptotic rate with the increment of saponin concentration, along with increased percentage of cells in S phase and decreased cells in G(2)/M phase in response to 10 or 30 microg/ml STCB treatment. At the concentration of 60 microg/ml, however, STCB resulted in an opposite effect on the cell cycles, presumably due to its interference with mitosis at high concentrations.

CONCLUSIONSSTCB inhibits the growth of S-180 cells both in vivo and in vitro possibly by inducing cell apoptosis and interfering with the cell cycle progression of the tumor cells.