The bortezomib/flavopiridol regimen induces apoptosis in imatinib mesylate-resistant LAMA84 cells exhibiting Lyn overexpression and diminished expression of Bcr/Abl. (A) LAMA84 (left) and LAMA84-R (right) cells were incubated in the presence of 5 nM bortezomib (Btzmb) ± flavopiridol (FP: LAMA, 150 nM; LAMA-R, 100 nM) for 24 hours, or 1 μM imatinib mesylate for 48 hours, after which percentage of cells exhibiting apoptotic morphology was determined by evaluating Wright Giemsa-stained cytospin preparations. Results represent the means ± SDs for 3 separate experiments performed in triplicate. (B) Cells were treated as described for panel A, after which cells were lysed and subjected to Western blot using the indicated primary antibodies. CF indicates cleavage fragment. Each lane was loaded with 30 μg protein; blots were stripped and reprobed with antibodies to actin to ensure equal loading and transfer. An additional 2 studies yielded equivalent results.