The effects of the carcinostatic agents on the cell cycle of Ehrlich ascites carcinoma cells.

The influence of tumor cell aging upon growth inhibition by carcinostatic agents was investigated with Ehrlich tumor in the form of ascitic cells. In the experiment on tumor growth, the rate of growth decreased with the lapse of time following tumor inoculation. The generation time of the 2-day old tumor was approximately 12 hours; that of the 6-day old tumor was approximately 42 hours. There were also significant differences in the DNA labeling index and mitotic index between the 2-day old and the 6-day old tumors, which were correlated with their generation times. Mitomycin-C affected more markedly the growth of the 2-day old fast growing tumor than that of the 6-day old tumor. Enhanced antitumor activity of the carcinostatic agent was seen when the drug was used during the rapidly growing stage of the Ehrlich ascites tumor.