Cytokinetic changes in the peripheral blood of leukemic patients during cytostatic therapy. V. Effect of VP 16 213 studied with flow cytofluorometry and cytoautoradiography

The cytokinetic effects induced by VP 16 213 (50-60 mg/sqm/12 hr for 10 doses) on the peripheral blood and bone marrow blasts of two patients with acute myelomonocytic leukemia have been studied using DNA flow cytofluorometry and in vitro tritiated thymidine cytoautoradiography. Besides a striking cytocidal effect, the drug induced cell synchronization in the G ₂ phase of the cell cycle as evidenced by the building up of tetraploid nuclei without an increase in mitotic figures. The synchronizing effect was greater in the bone marrow than in peripheral blood. In one patient, a removal of the G ₂ block was observed which paralleled an increase in proliferative activity. The usefulness of flow cytofluorometry for rapidly detecting the cytokinetic changes induced in acute leukemia blasts by cytostatic drugs is affirmed.