Flow cytometric analysis of adriamycin-perturbed mouse mammary tumors

The effects of a single intraperitoneal injection of adriamycin (10 mg/kg) on a fast-growing C3H mouse mammary tumor (S102F) have been analyzed volumetrically, biochemically, autoradiographically and flow cytometrically. Mathematical simulation of the data was also used to aid in the interpretation of the recovery kinetics. This dose of adriamycin did not induce regression in tumor volume but did inhibit the growth rate for 4-5 days. 3H-TdR incorporation was gradually inhibited to reach a low of 20% of control at 24 and 36 hr and then recovered back to control by 96 hr after adriamycin treatment. The flow cytometric analysis also showed a marked reduction in the relative fraction of cells in the S-phase with a minimum of 23% of control at 72 hr; however, in contrast to the 3H-TdR incorporation data, the fraction of cells in the S-phase was only at 39% of control at 96 hr after the adriamycin injection. Since the 3H-TdR incorporation data disagreed with the flow cytometry data, autoradiographic analysis was also done at selected times after the adriamycin injections, and qualitatively, this analysis confirms the flow cytometry data in that the labeling index was 29% of control at 96 hr after adriamycin. The mitotic index also dropped from 8 to 1%, respectively, for controls and at 96 hr posttreatment. The degenerate index was about 1% in control tumors and no increase was observed in treated tumors. Adriamycin-induced cell-cycle delay occurs predominately in G1 and G2 but there is also an apparent minor delay in the transit across the S-phase and some apparent cytotoxicity in G2 and/or M. The long delay in volumetric growth appears to be due to the extended cell-cycle delay rather than extensive cell killing.