Taxol is an investigational antineoplastic agent which acts by stabili
zing microtubules, thereby preventing normal mitosis. It is believed t
o block cells in the G(2)/M phase of the cell cycle. The drug is a nat
ural product isolated from the yew, Taxus brevifolia. We have used a c
ell line derived from human cervical carcinoma to investigate the comb
ination of Taxol with high and low dose rate Cs-137 irradiation. An ad
ditive effect for Taxol plus radiation was observed; supra-additivity
or synergism is not suggested by our data. In the cell line studied, d
rug concentrations that accumulate cells to some degree in the G(2)/M
phase of the cycle lead to cell lethality, so that no radiosensitizing
effect is possible. We have also shown that the cytotoxic effect of T
axol is not limited to the G(2)/M phase of the cell cycle. In the clin
ic, Taxol shows promise both as a chemotherapeutic agent and as a poss
ible adjunct to radiation. The present work demonstrates the need for
further studies of Taxol plus radiation with a variety of human cell l
ines of normal and malignant origin.