Effect of combination treatment on the induction of DNA fragmentation in Bcr-Abl-expressing cells. Both 32D (A) and FL5.12 (B) vector control cells (bars 1-4) or p185-expressing cells (bars 5-8) were either not treated (□) or treated with MPA alone (▪;1 μM for 32D, 0.5 μM for FL5.12) or imatinib alone (▦;1 μM for 32D, 0.5 μM for FL5.12 cells) or the combination of MPA and imatinib (▨) for 16 to 20 hours, and apoptosis was measured by the Cell Death Detection ELISA method. Data represent mean ± SD of 3 independent experiments. ELISA assays were performed in duplicate.