FLOW CYTOMETRIC STUDY OF THE APOPTOSIS IN -VITRO INDUCED BY ANTHRACYCLINES, ARA-C AND MITOXANTRONE ON THE U937 LINE

A flow cytometric method for the simultaneous apoptotic cell detection and cell cycle analysis was applied on the U937 cell line. Four antit umoral drugs currently used in the treatment of acute non lymphocytic leukemia (two anthracyclines, mitoxantrone and ara-C) were studied and the concentration which induce 50% of apoptosis (AC50) was calculated for each drug. Our results clearly show a dissociation between the cy tostatic effect (the block in the cell cycle observed for low drug con centrations) and the cytotoxic effect (the induction of apoptosis indu ced by higher concentrations) of all the tested molecules. On an other hand, the four molecules induced apoptosis during the G1 phase of the cell cycle. The method was found suitable to evaluate the in vitro ef fect of drugs and could be adapted as a predictive assay of the respon se of blast cells to chemotherapy.