SCF protects erythroid precursors from drug-induced apoptosis. Day-7 erythroblasts were incubated with 50 ng/mL camptothecin (CPT), 2 μM etoposide 7 erythroblasts were incubated with 50 ng/mL camptothecin (CPT), 2 μM etoposide percentage of cell death was determined after 12, 24, and 48 hours. Where indicated (+SCF) cells were preincubated for 2 days with 100 ng/mL SCF and kept in the presence of SCF during incubation with chemotherapeutic drugs. A typical experiment of 6 performed with cells from different donors is shown.