Flow cytofluorometric analysis of the effects of new nitrosourea derivatives on proliferation of EMT 6 tumor cells "in vitro".

Examined by flow cytofluorometric analysis, the DNA distribution of EMT 6 tumor cells was highly perturbed after one hour of in vitro incubation with: RPCNU, RFCNU, chlorozotocin (CZT) or 185 (CNCC), four new nitrosourea derivatives. After the treatment with chlorozotocin (20 micrograms/ml) and CNCC (50 micrograms/ml), most of cells were in G2 + M phase and this accumulation lasted more than 48 hours without any restoration before 72 hours. RPCNU (20 micrograms/ml) and RFCNU (50 and 65 micrograms/ml) induced and accumulation of cells in G2 + M phase during 24 hours. The normal state was regained after 48 hours. These reduced rate of progression of the cells through S phase and the G2 block observed after exposure to the new compounds, should, in part, explain their antitumoral activity.