Flow Cytometric Analyses of the Characteristics of Tumor Cells Treated with Two Platinum Compounds: 1,1‐Cyclobutanedicarboxylato(2‐aminomethylpyrrolidine)‐platinum(II) and Cisplatin

In order to reduce the toxicities of cisplatin (DDP) and/or to improve antitumor efficacy, a large number of new platinum analogues have been synthesized. 1,1‐Cyclobutanedicarboxylato(2‐amino‐methylpyrrolidine)platinum(II) (DWA2114R) is one of them. In this study, we characterized the action mechanism of DWA2114R flow‐cytomctrically in 3 human lung cancer cell lines by using bromodeoxyuridine (BrdUrd), rhodamine 123 (Rho) and Ki‐67 antibody (Ab), and compared the results with those for DDP. We found that the actions of these 2 platinum analogues were characteristically different at the subcellular level. Our observations may be summarized as follows, a) Simultaneous exposure of cells to DDP and BrdUrd resulted in decreases in fluorescence intensity, i.e. in the amount of BrdUrd incorporated into single‐stranded DNA. b) DDP appears to be approximately 20‐fold more active than DWA2114R in producing cell cycle perturbation, c) In PC‐6 small cell carcinoma cells, DDP induced decreases in S phase cells and accumulation of cells in the G2M phase, whereas in PC‐10 squamous carcinoma and PC‐3 adenocarcinoma cells DDP produced S phase cell accumulation. Weak but similar changes occurred with DWA2114R. d) The high Ki‐67 antigen cell population was decreased by treatment with either DDP or DWA2114R, but DDP reduced the low Ki‐67 antigen population more than DWA2114R. e) In PC‐10 and PC‐d cells, DDP suppressed Rho incorporation into live mitochondria, whereas DWA2114R produced no change in Rho incorporation. PC‐3 cells were not affected by either DDP or DWA2114R. It is likely that these differences reflect the biological activities of DDP and DWA2114R.