CD34 and acute myeloid leukemia: As shown during our initial screen, the cardiac glycosides strophanthidin, digoxin and ouabain are effective against 8227 AML cells in the nanomolar range, with high toxicity towards CD34+ CD38− cells (LC50: strophanthidin = 23.25 nM, digoxin = 23.19 nM, ouabain = 11.61 nM) (Fig. 2d).