Both caspase-8 and caspase-9 are involved in HF-ATS-induced apoptosis. (A) Expression of cleaved capase-8 and caspase-9 in HCT116 and DLD-1 cells treated with combination of HF (10 nM) and ATS (160 μM) for 24 h. (B, C) For caspase 8 inhibitor (z-IETD-fmk) pretreated cells, HF-ATS increased the number of apoptotic cells. In B, flow cytometry analyses of apoptosis regulated by combination of HF (10 nM) and ATS (160 μM) for 24 h in HCT116 and DLD-1 cells pretreated with caspase-8 inhibitor (z-IETD-fmk). In C, apoptosis was quantified with flow cytometry. * P < 0.05, ** P < 0.01, compared with control group. a P < 0.05, aa P < 0.01, compared with HF. b P < 0.05, bb P < 0.01, compared with ATS. (D) Expression of cleaved capase-8, capase-9, caspase-3 and PARP regulated by combination of HF (10 nM) and ATS (160 μM) for 24 h in HCT116 and DLD-1 cells pretreated with caspase-8 inhibitor (z-IETD-fmk). (E, F) For caspase-9 inhibitor (z-LEHD-fmk) pretreated cells, HF-ATS increased the number of apoptotic cells. In E, flow cytometry analyses of apoptosis regulated by combination of HF (10 nM) and ATS (160 μM) for 24 h in HCT116 and DLD-1 cells pretreated with caspase-9 inhibitor (z-LEHD-fmk). In F, apoptosis was quantified with flow cytometry. ** P < 0.01, compared with control group. aa P < 0.01, compared with HF. bb P < 0.01, compared with ATS. (G) Expression of cleaved capase-8, capase-9, caspase-3 and PARP regulated by combination of HF (10 nM) and ATS (160 μM) for 24 h in HCT116 and DLD-1 cells pretreated with caspase-9 inhibitor (z-LEHD-fmk).