SK1-I induces apoptosis in primary AML blasts. (A) Primary blasts from 2 patients with AML (FAB classification F2; > 70% blasts) and peripheral blood mononuclear leukocytes from 2 healthy donors (B) were obtained as described in “Cells and cell culture,” cultured in medium containing 10% serum for 24 hours in the absence or presence of the indicated concentrations of SK1-I. Cells were stained with annexin V/PI and apoptosis determined by flow cytometry.