Combination of imatinib with HI acts synergistically only in BA/F3p210 cells with moderate resistance to imatinib. (A-D) MTT assay. Isobolograms for the effects of imatinib and CPX or GC7on BA/F3p210 M351T (A-B) and BA/F3p210 T315I (C-D) cells, respectively, after 48 hours. (E-H) Apoptosis. Cotreatment with imatinib and CPX (C) or GC7 (D) induced more apoptosis in BA/F3p210 M351T cells. Apoptotic cell fractions were measured by PI staining. Values (mean ± SD of 3 experiments) are depicted as bar graphs.