Effect of combination treatment on S6 phosphorylation. 32D-p185, FL5.12-p185, LAMA84, and K562 cells were treated with the indicated concentrations of MPA and/or imatinib for 3 hours (for 32D- and FL5.12-p185 cells) and 24 hours (for LAMA84 and K562 cells). Western blots were probed with antibody specific for phospho-S6 ribosomal protein (p-S6). Duplicate gels were probed with antibody specific for total S6 (t-S6). This is representative of 3 independent experiments.