Cellular Retention of TKI and Apoptosis Commitment Figure 5. Kinetics and dynamics of BCR-ABL signaling upon tyrosine-kinase inhibition. K562 cells were treated with increasing concentrations of tyrosine kinase inhibitors. Untreated cells served as a control. For analysis of signaling pathway inhibition cells were either lysed for Western Blot analysis or fixed for FACS. (A): Left panel: Western Blot analysis of signaling pathway inhibition after exposure of Ba/F3-BCR-ABL cells to imatinib for 2 h. Right panel: FACS analysis of STAT5 and CRKL inhibition using phosphorylation-specific antibodies. To assess signaling dynamics, this analysis was performed at three different time-points (0.3, 2, and 12 h). (B) The same analysis was performed using the second-generation BCR-ABL tyrosine kinase inhibitor dasatinib. Experiments were performed at least in triplicate and one representative experiment is shown. doi:10.1371/journal.pone.0040853.g005 PLoS ONE | www.plosone.org 8 July 2012 | Volume 7 | Issue 7 | e40853