Combined treatment with IM and SB216763 is cytotoxic by inducing apoptosis in CML CP stem/progenitor cells. CML and normal CD34⁺CD38⁻ primitive and CD34⁺CD38⁺ committed progenitors were labeled with CFSE and cultured for 96 hours with IM (1μM), SB216763 (5μM), or the combination. (A) Representative data for apoptosis of CML CD34⁺CD38⁻ primitive and CD34⁺CD38⁺ committed progenitors. (B-C) Compiled data (expressed as percentages of cells positively labeled by annexin V–PE) for apoptosis of total and undivided CML and normal CD34⁺ cell subsets (n = 5), respectively.