Effect of imatinib on STAT5 phosphorylation in K562 and K562/DOX.

(A) Cells were incubated during 2 hours with escalating doses of imatinib with or without verapamil (VP) and total protein lysates were immunoblotted with an antibody against phosphorylated STAT5 (P-STAT-5). (B) Percentage of STAT5 phosphorylation in the presence of different concentrations of imatinib relative to the control (0 μM) cultures, as calculated by the phopho-STAT5/actin densitometric ratio of the respective bands.