THE EFFECT OF 9,11-SECOSTEROL, A NEWLY DISCOVERED COMPOUND FROM THE SOFT CORAL GERSEMIA-FRUTICOSA, ON THE GROWTH AND CELL-CYCLE PROGRESSIONOF VARIOUS TUMOR-CELLS IN CULTURE

A new 9,11-secosterol, -3beta,6alpha-dihydroxycholest-7,22(E)-dien-9-o ne, was found to exhibit growth inhibitory (IC50 below 10 muM) and cyt otoxic activities against human leukemia K562, human cervical cancer H eLa, and Ehrlich ascites tumor cells in vitro. The cytostatic concentr ations of the compound generally caused the G2/M block in the cell cyc le progression, but differences between the three tumor cell lines in the events leading to cell death were remarkable. While inhibiting cel l proliferation, 9,11-secosterol caused accumulation of HeLa and K562 cells in the metaphase of mitosis. So, abnormal mitosis can play an im portant role in the cytotoxicity of 9,11-secosterol in these cell line s. In the Ehrlich ascites tumor cell line the increasing concentration s of the drug (up to 40 muM) did not cause an immediate cell killing. Instead, due to continued DNA synthesis without entry into mitosis, ce lls with high DNA ploidy were produced. It was shown that the cytoskel etal systems such as microtubules and microfilaments were not damaged by the action of 9,11-secosterol. Further studies are necessary to elu cidate the mechanism of the cytotoxic effect of 9,11-secosterol.