c-Abl inhibition decreases ABCB1 expression and activity.

<p>(<b>A</b>) Cells were treated with imatinib (72 h), washed, treated with doxorubicin (30′) in the absence of imatinib, and intracellular doxorubicin fluorescence assessed by FACS. The experiment was performed ≥3 times; a representative experiment is shown. (<b>B</b>) Cells were drug- treated (72 h), and viability was assessed. Graph is representative of 3 independent experiments. Some error bars are too small to visualize. PTX = paclitaxel (30 nM), Cam = camptothecin (1 µM), Cis = cisplatin (20 µM), 5-FU = 5-fluorouracil (500 µM). (<b>C,D</b>) Western blot analysis. Lysate from MCF-7 cells transfected with ABCC1 served as a positive control for ABCC1 expression. Blots are representative of ≥3 independent experiments. (<b>D</b>) Cells were imatinib or nilotinib-treated (48 h, left) or transfected with siRNAs (right), and lysates blotted with the indicated antibodies. Mean±SEM from 3 independent experiments (below). (<b>E</b>) siRNA-transfected cells were treated with doxorubicin (30′), washed, and intracellular doxorubicin fluorescence assessed. Graph is representative of 3 independent experiments. Representative Western blot (right). (<b>F, G</b>) Cells were treated with either doxorubicin (<b>F</b>) or rhodamine 123 (<b>G</b>) in the presence of the ABCB1 inhibitor, verapamil, or imatinib for 30′, washed, and incubated with verapamil or imatinib for an additional 45′, and rhodamine 123 or doxorubicin intracellular fluorescence assessed by FACS. Graphs are representative of 3 independent experiments. *<i>p</i><0.05, **<i>p</i>≤0.01, ***<i>p</i><0.001 (see methods). n.s. = not significant.