HI inhibits proliferation of Bcr-Abl–positive and –negative human leukemic cells in a dose-dependent fashion. K562 and HL-60 cells were exposed to the indicated concentrations of CPX (A-B) and GC7 (C-D), for 24, 48, and 72 hours (black, gray, and hatched bars, respectively). CPX and GC7 impaired the proliferation of all tested cells independent of Bcr-Abl status. Data shown are mean ± SD of 3 independent experiments. The percentage of cell growth was normalized to the growth of cells in the absence of drug treatment.