Induction of cell arrest at G1/S and in G2 after treatment of Ehrlich ascites tumor cells with metallocene dichlorides and cis-platinum in vitro.

The influence of in vitro application of the cytostatic agents titanocene dichloride (TDC), vanadocene dichloride (VDC), and cis-diamminedichloroplatinum(II) (DDP) on the cytokinetic behavior of EAT cells was investigated. All three substances induced similar cytokinetic phenomena that are characterized, on the one hand, by an accumulation of cells in the late S phase and in the G2 phase during exposure periods of 8 to 20 h. On the other hand, some cells were apparently arrested at the end of the G1 phase and, after removal of the cytostatic agents, moved through the following S, G2, and M phases as synchronized cell populations. In view of this unusual cytokinetic pattern of multiple effects, it is argued that the striking similarities in cytokinetic behavior after treatment with the three different cytostatic substances indicate analogies in their molecular mechanisms of action. The different alteration patterns observed after in vivo application of the drugs are obviously due to additional processes occurring only in vivo.