Effect of combination treatment on Src and Lyn phosphorylation. (A) 32D-p185, FL5.12-p185, K562, and LAMA84 cells were treated with the indicated concentrations of MPA and/or imatinib for 90 minutes (for 32D- and FL5.12-p185 cells) and 24 hours (for K562 and LAMA84 cells). Total cell lysate (30 μg) was used in each lane. Western blots were first probed with anti-phospho-Src antibody. Membranes were washed and reprobed with an antibody to detect total levels of Lyn (t-Lyn). This result is representative of 3 independent experiments. (B) 32D-p185 cells were treated with individual drugs or the combination of drugs as indicated for 3 hours. Lysate was immunoprecipitated with anti-Lyn antibody and blotted with an antibody (4G10) specific for tyrosine phosphorylated proteins (p-tyr). Lysate precipitated with protein A beads in the absence of Lyn antibody (IP control), and total lysate are shown in the last 2 lanes.