Compound K induced the apoptosis of HL-60 cells via caspase activation. (A) Cells were treated with 20 μM of Compound K for the indicated times. Caspase-8, caspase-9, caspase-3, and PARP were analyzed by Western blotting. β-actin was used as an internal control. Experiments were repeated three times and similar results were obtained. (B) Effects of the caspase inhibitors (z-VAD-fmk, z-DEVD-fmk, z-IETD-fmk and z-LEHD-fmk) on apoptosis were determined by testing for Compound K-induced DNA fragmentation. HL-60 cells were pretreated with/without 50 μM z-VAD-fmk, 100 μM z-DEVD-fmk, 100 μM z-IETD-fmk or 100 μM z-LEHD-fmk for 1 h, and then treated with Compound K (20 μM for 2 h). DNA fragmentation was measured by DAPI staining. White square: None, Black square: Compound K. The data presented are the means ± SD of results obtained from three independent experiments. ***P < 0.001 vs. control group, ††
P < 0.01, †††
P < 0.001 vs. the Compound K-treated group; significances were determined using the Student's t-test.