Reduction of 1-ß-d-arabinofuranosylcytosine and adriamycin cytotoxicity following cell cycle arrest by anguidine

The protein synthesis inhibitor anguidine induced a frozen cell cycle state in exponentially growing Chinese hamster ovary cells, as demonstrated by serial DNA flow cytometric measurements in the absence and presence of Colcemid as a stathmokinetic agent. The minimally effective concentration of anguidine for induction of cell cycle arrest was 0.1 µg/ml. As demonstrated by tritiated thymidine labeling index and DNA flow cytometric investigations in the presence of Colcemid, a 4-hr exposure of Chinese hamster ovary cells to ≥4 µg of anguidine per ml effected a >12-hr cycle perturbation at no cytotoxic expense. Preincubation of exponentially growing Chinese hamster ovary cells for 4 hr with 5 µg of anguidine per ml reduced the cytotoxicity from Adriamycin (1 hr; 0.1 to 10 µg/ml) and from 1-ß-D-arabinofuranosylcytosine treatment (18 hr; 5 to 50 µg/ml) by 10- to 100-fold. Further investigation of the concentration dependence and time course Of this protective effect of anguidine revealed a plateau at 1 µg of anguidine per ml and lack of protection in case of anguidine exposure subsequent to Adriamycin and 1-ß-D-arabinofuranosylcytosine treatment. Prolongation of the treatment-free interval between initial anguidine exposure and 1-hr Adriamycin treatment demonstrated partial recovery of DNA synthesis associated with some loss in cytoprotection. Our results indicate that the largely indiscriminate interference with cycle progression by anguidine under noncytotoxic conditions affords significant protection against 1-ß-D-arabinofuranosylcytosine and Adriamycin-re-lated cytotoxicity, the degree of which appears to be related to the extent of reduction in cycle traverse rate. Thus, anguidine may serve as a useful probe to study in detail drug-induced lethal injury as a function of cycle traverse rate.