Radiobiological effects of docetaxel (Taxotere): a potential radiation sensitizer

To investigate the ability of docetaxel (Taxotere) to radiosensitize human cell lines of differing malignant status, intrinsic radiosensitivity and p53 status.

Cell survival following treatment with drug and/or radiation was determined by colony-forming assay on two malignant human colon cell lines of widely different radiosensitivity (HT29 and SW48). An immortal human keratinocyte line (HaCaT), which does not form tumours in nude mice, was used to assess the effect on non-malignant human epithelium.

The experiments indicate that docetaxel had the greatest cytotoxic and radiosensitizing effect on the SW48 (p53wt) cell line. The degree of radiosensitization was not improved by increasing the drug concentration, although the overall cytotoxicity was increased with increasing concentrations of the two agents. Both p53mut lines were less sensitive to the drug, irrespective of their malignant potential.

The results support a role for Taxotere as a weak radiosensitizer of the three cell lines tested. The p53 status and intrinsic radiosensitivity may be relevant to the mechanism.