THE COMPOUND 14-KETO-STYPODIOL DIACETATE FROM THE ALGAE STYPOPODIUM FLABELLIFORME INHIBITS MICROTUBULES AND CELL-PROLIFERATION IN DU-145 HUMAN PROSTATIC CELLS

We investigated the effects of the drug 14-keto-stypodiol diacetate (S DA) extracted from the seaweed product Stypopodium flabelliforme, in i nhibiting the cell growth and tumor invasive behavior of DU-145 human prostate cells. In addition, the molecular action of the drug on micro tubule assembly was analyzed. The effects of this diterpenoid drug in cell proliferation of DU-145 tumor cells in culture revealed that SDA at concentrations of 5 mu M decreased cell growth by 14%, while at 45 mu M a 61% decrease was found, as compared with control cells incubate d with the solvent but in the absence of the drug. To study their effe cts on the cell cycle, DU-145 cells were incubated with increasing con centrations of SDA and the distribution of cell-cycle stages was analy zed by flow cytometry. Interestingly, the data showed that 14-keto-sty podiol diacetate dramatically increased the proportion of cells in the G2/M phases, and decreased the number of cells at the S phase of mito sis, as compared with appropriate controls. Studies on their action on the in vitro assembly of microtubules using purified brain tubulin, s howed that SDA delayed the lag period associated to nucleation events during assembly, and decreased significantly the extent of polymerizat ion. The studies suggest that this novel derivative from a marine natu ral product induces mitotic arrest of tumor cells, an effect that coul d be associated to alterations in the normal microtubule assembly proc ess. On the other hand, a salient feature of this compound is that it affected protease secretion and the in vitro invasive capacity, both p roperties of cells from metastases. The secretion of plasminogen activ ator (u-PA) and the capacity of DU-145 cells to migrate through a Matr igel-coated membrane were significantly inhibited in the presence of m icromolar concentrations of SDA, These results provide new keys to ana lyze the functional relationships between protease secretion, invasive behavior of tumor cells and the microtubule network.