Identification of apoptotic and necrotic human leukemic cells by flow cytometry

Glucocorticoids kill human leukemic cells, CCRF-CEM.f2, by apoptosis. Cell death is preceded by DNA fragmentation into nucleosomal subunits which can be evaluated by DNA gel electrophoresis or by determining the proportion of cleaved DNA in whole cell lysates. Hyperthermic treatment of CCRF-CEM.f2 cells induces necrotic cell death which is characterized by a different DNA gel electrophoretic pattern. However, these techniques cannot distinguish the individual contributions of both forms of death in a heterogeneous population. Therefore, we have developed a flow cytometric method that readily distinguishes apoptotic and necrotic cells on the basis of propidium iodide staining and cellular light scatter characteristics. This method can be used to analyze factors influencing the mechanisms of cell death after cytotoxic drug treatment.