Imatinib mesylate inhibits autophosphorylation of Bcr-Abl tyrosine kinase and depletes the levels of p-HSF-1 and hsp70 levels in K562 and Jurkat/Bcr-abl cells. (A) Jurkat/Bcr-Abl cells and K562 cells were treated with 0.25 μM or 2.0 μM imatinib for 24 hours. Cell lysates were collected and immunoprecipitated with Bcr-abl antibody and immunoblotted with anti–p-tyrosine antibody. (B) Following treatment with total cell lysates were immunoblotted with p-tyrosine, HSF-1, p-HSF-1, and hsp70 antibodies. (C) Following treatment with 0.5 or 1.0 μM wortmannin, AKT was immunoprecipitated from cell lysates and allowed to phosphorylate GSK-α/β, which was analyzed by Western blotting using an anti–phospho-GSK-3α/β (serine 21/9) antibody. Cell lysates also were immunoblotted with anti-hsp70 antibody. β-actin levels were used as loading control. (D, E) Indicated cell types were treated with Ara-C (D) and etoposide (E) at the indicated concentrations for 24 hours. Following these treatments, the percentages of apoptotic cells were determined by annexin-V staining followed by flow cytometry. Values represent the mean ± SE of 3 experiments. (F) K562 and Jurkat/Bcr-Abl cells were incubated with the indicated levels of imatinib and/or Ara-C or Apo-2L/TRAIL for 24 hours. Following these treatments, the percentages of apoptotic cells were determined by annexin-V staining followed by flow cytometry. Values represented by the bars indicate the mean ± SE of 3 experiments.