Combination of paclitaxel and radiation: genotoxicity in vitro in four mammalian cell lines

Paclitaxel is an antimicrotubular agent that blocks the cells in the GUM ph ase of the cell cycle. Due to this action, it is presumed that this drug co uld function as a radiation sensitizer. We studied the genotoxic effects of a combination of paclitaxel and radiation in four mammalian cell lines in the micronucleus assay. The results do not show a clear radiation-sensitizi ng effect. In the three cell lines, L5178Y, V79 and HeLa, the micronucleus frequencies varied around a theoretical additive effect of the single treat ments (paclitaxel or radiation alone). Only the human breast cancer cell li ne MCF-7 showed consistently lower than additive micronucleus frequencies, although the deviation was not significant. Overall, it remains inconclusiv e whether paclitaxel exerts a radiosensitizing effect and, if so, whether t his effect depends on the cell type or other characteristics of tumor biolo gy. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.