Effect of combination treatment on Stat5 phosphorylation. 32D-p185 (A), FL5.12-p185 (B), K562 (C), and LAMA84 (D) cells were treated with indicated concentrations of MPA and/or imatinib for 90 minutes (for 32D- and FL5.12-p185) or the indicated times for K562 and LAMA84 cells. Thirty μg of total cell lysate was loaded in each lane, and Western blot analysis was performed using an antibody specific for phospho-Stat5 (p-Stat5). Duplicate gels were probed with antibody specific for total Stat5 (t-Stat5). 32D-p185 and FL5.12-p185 results are representative of 4 and 3 independent experiments, respectively. K562 and LAMA84 results are representative of 2 independent experiments; treatment for 24 hours was repeated 3 times.