Cytokinetic effects of l,2-bis(4-isobutoxycarbonyloxymethyl-3, 5-dioxopiperazin-l-yl) ethane (MST-16) on leukemia L1210 cells in mice

MST-16 is a new antitumor agent. which was first synthesized by Cai JC in China. The cytokinetic effects of MST-16 on leukemia L1210 cells were studied with autoradiography and stathmo-kinetic technique. By means of the method of percentage of labeling mitosis (PLM). the values of the cell cycle of logarithmically growing cells were obtained: Tc = 16.5 h, Tai = 2.1 h, Ts = 10.2 h, Taz = 3.7 h, and Tvi = 0.5 h. The PLM curve became irregular. flattened and shifted to the right, and the prolongations of Tc. Toz and Ts after the treatment with MST-16 were evident. With mitotic index (MI) method. the blockage of G2 phase cells to M phase by MST-16 was shown. Using the pulse or continuous labeling technique. Taz. Ts and Tai were estimated as 2.1 h. 10.5 h and 3.0 h respectively, and the prolongations of Toz, Ts and Tai by MST-16 were further proved. The percentage of the cells in GO phase on d 9 was 32.5% after continuous labeling for 24 h, and MST-16 had no detrimental effect on them. Razoxane and l,2-bis (3,5-dioxopiperazin-l-yl) ethane (ICRF-154) could prolong both Taz and Ts but ICRF-154 was less potent at the same dose level. probimane could prolong Ts and elicited no effect on Taz.