Effects of imatinib on c-kit tyrosine-phosphorylation and SCF-induced phosphorylation of Akt. PB was taken before start with imatinib. MNCs were separated and treated with SCF (100 ng/mL), imatinib (1 μM), and in combination for 15 minutes. As a control, the SCF-dependent leukemic cell line Mo7e was used. Whole cell lysates were prepared and immunoblotted using an antiphosphotyrosine c-kit antibody (A) or an antiphospho-Akt antibody (B). To control equal loading, the blot was stripped and reprobed with anti–c-kit (A) or Akt (B). Shown is a representative result of a total of 5. Arrows indicate the position of the 160-kD isoform of c-kit (A) and of Akt (B), respectively.