Taxol, radiation, and oncogenic transformation.

The novel antineoplastic drug taxol has been shown to be active clinically against several types of human tumors. With improvement in treatment strategy and the number of long-term survivors increasing, a question that needs to be addressed is the potential carcinogenic effect of the treatment in the induction of second malignancies. We show here that when tested using an in vitro assay for oncogenic transforming potential, taxol is ineffective in focus induction at doses significantly higher than those used in the clinic. However, taxol enhances the oncogenic potential of gamma-rays in a synergistic fashion. The fact that taxol blocks cells at the G2/M phases of the cell cycle may account for this interaction since G2/M are relatively radiosensitive phases of the cell cycle.