Morphological studies on the effect of taxol on cultured human prostatic cancer cells

The effect of taxol, an experimental antitumor drug, was studied in vitro on human prostatic cancer cells. Different concentrations of taxol, varying from 5 microM to 0.01 nM, were used. The effect of taxol was examined by light and electron microscopy. Taxol had a marked cytotoxic effect on prostatic cancer cells down to a 10 nM concentration of taxol when observed by light microscopy. However, by electron microscopy, the specific effect of taxol was seen even with a 1 nM concentration of taxol. Taxol induced the appearance of numerous round cells after a few days and, subsequently, progressive death of the tumor cells. Among the surviving tumor cells, large tumor cells were noted as well as many multinucleated tumor cells. By electron microscopy, the round tumor cells showed mitotic figures with a high amount of cytoplasmic microtubules. Nonmitotic cells were often multinucleated and contained a high number of cytoplasmic microtubules and microtubule-related structures. The results show that taxol, even at very low concentrations, has a highly cytotoxic effect on prostatic cancer cells; and when a very low concentration of taxol is used with no obvious cytotoxic effect at the light microscopic level, specific taxol-induced ultrastructural alterations can be observed.