Effect of imatinib on the proliferation and phosphorylation of

MDR1-transduced AR230 cell line. (A) Proliferation of AR230 and AR230/MDR cells after 3 days of culture in the presence or absence of 1 μM imatinib, as assessed by MTS uptake. (B) STAT5 phosphorylation assessed by Western blot after a 2-hour incubation with imatinib. The bottom panel shows the percentage of STAT5 phosphorylation in the presence of different concentrations of imatinib relative to the control (0 μM) cultures, as calculated by the phospho-STAT5/actin densitometric ratio of the respective bands.