Anti-neoplastic activity of paclitaxel on experimental superficial bladder cancer: in vivo and in vitro studies.

The effects of intravesical administration of paclitaxel (taxol) in a bladder tumor model in mice, as well as the drug's in vitro activity on the same tumor cells, have been studied. Two cell lines, derived from MBT-2 cells, were employed in these experiments. The T50 line (obtained by many passages in mice) was much more aggressive in vivo than the T5 line. In vivo paclitaxel treatment for 3 days after T5 implantation resulted in a considerable retardation of tumor growth, whereas under the same conditions the T50 line was much less, although still significantly, affected. When treatment was started 1 day after tumor implantation, both tumor variants were affected by paclitaxel to the same extent. The in vitro experiments utilized the MiCK assay, which allows continuous recording of the kinetics of cell growth. These studies revealed a 39.8% inhibition of cell growth by 2.10(-8)M paclitaxel in the T50 line and a 30-fold increase in concentration had only a small additional effect on the degree of inhibition. At 2.10(-8)M paclitaxel, growth of T5 was inhibited by 21.7%, which increased to 35.2% at 6.10(-7)M. The treated cells displayed bundles of microtubuli, as described for other paclitaxel-treated cells.