Figure 2. Inhibition of phospho-CRKL by imatinib in CML stem and progenitor cells.

(A) Phospho-CRKL levels in normal CD34⁺ cells were compared with CML CD34⁺ cells treated or not with imatinib. Total CRKL and actin are shown as loading controls. (B) Phospho-CRKL and (C) phospho-STAT5 immunoblots with lysate from sorted CD34⁺CD38⁺ and CD34⁺CD38^– CML cells treated 4 hours with or without 5 μM imatinib demonstrated inhibition of BCR-ABL by imatinib in both populations. Total CRKL and total STAT5 are shown as respective loading controls. (D) Phospho-CRKL, phospho-STAT5, and phospho-AKT immunocytochemical stains of sorted CD34⁺CD38^– and CD34⁺CD38⁺ CML cells treated 4 hours with or without 5 μM imatinib demonstrated BCR-ABL inhibition in all cells within the population. Representative cells are shown. Identical data were obtained for a second sample (not shown).