Effect of IM, LMB, or their combination on the proliferative capacity of normal or Ph-positive myeloid progenitors. (A) CD34-positive cells isolated from 6 healthy donors and (B) myeloid progenitors from 35 patients with CML were either left untreated (NT) or exposed to IM, LMB, or a combination of the 2 drugs(I+L) following the schedule indicated in Figure 1. Cells were then plated in methylcellulose media and after 21 to 28 days total number of BFU-E and CFU-GM colonies was determined for each experimental condition. Data are presented as percentage of variations in total colony number with NT cells arbitrarily set at 100%. (C) Average number of colonies derived from healthy (○) or CML (•) cells.