The micronucleus assay: an evaluation of its use in determining radiosensitivity in vitro

The cytokinesis-block micronucleus assay was used to measure radiosensitivity in vitro in a panel of seven cell lines. Six of these cell lines were used to study the major parameters of this assay. We observed varying sensitivities following cytochalasin-B exposure. Treatment with 1 microgram/ml cytochalasin-B for 24 h reduced cell survival in four of the six cell lines by > 60%. Cytochalasin-B concentration and post-irradiation culture time were both found to influence cell-response. In three cell lines (V39, V134 and HX142), a decrease in cytochalasin-B concentration (2-0.5 microgram/ml) resulted in an increase in the frequency of radiation-induced micronuclei per binucleate cell. In other cell lines, either the opposite (V7M, CHO-K1) or no effect (WiDr) was seen. A linear dose-response was observed between induced damage expressed as the frequency of micronuclei and radiation dose in all but one melanoma (V39) cell line. Evidence for radiation-induced division-delay, with the maximum frequency of binucleation in irradiated cultures occurring 24-48 h after that of controls, was only seen in two cell lines. Of particular note, and in contrast to some other published reports, was the lack of a general correlation between cell-response measured in the clonogenic and the cytokinesis-block micronucleus assays. Consideration of lethal lesions, determined from the clonogenic dose-response curve, with respect to micronucleus frequency showed a complex relationship, with one micronucleus per binucleate cell corresponding to a wide range of lethal lesions depending on the cell line.(ABSTRACT TRUNCATED AT 250 WORDS)