Involvement of caspase-3, -8, and -9 in ferrugone and DMI-induced cell death in human ovarian cancer cells. (A,B) A2780 cells were pretreated with caspase-3 inhibitor z-DEVD-fmk (75 µM), caspase-8 inhibitor z-IETD-fmk (50 µM), and caspase-9 inhibitor z-LEHD-fmk (75 µM) for 2 h, and then treated with ferrugone (A) and DMI (B) (0.5 µM) for 24 h. MTT assay was performed to determine cell death. (C,D) A2780 cells were treated with ferrugone (C) and DMI (B) (0.25, 0.5, and 1 µM) for 48 h. Cleaved caspase-3 and caspase-8 levels were determined by Western blot assay. β-actin was used as an internal control. The data are representative of three independent experiments. Student’s t-test (two-tailed) was applied to evaluate the significance. # p < 0.05 as compared with the untreated group. * p < 0.05 as compared with the ferrugone or DMI only-treated group.