HCPT activates the intrinsic and extrinsic apoptotic pathways. (A) 10-hydroxycamptothecin (HCPT) increased the activity of caspase 3. SW1116 cells were treated with 2.5 μg/mL HCPT for 48 hours. Cells were harvested for caspase 3 activity assay. The data are the means ± SD from two independent experiments. *P < 0.01, compared to PBS group. (B) HCPT activated the intrinsic and extrinsic apoptotic pathways. SW1116 cells were treated with 2.5 μg/mL HCPT for 48 hours. Protein expressions were determined by western blot. (C) HCPT induces apoptosis in a caspase-dependent manner. SW1116 cells were pre-treated with z-DEVD-fmk for 2 hours and then treated with HCPT (10 μg/mL) for another 48 hours. Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. The data represent the means ± SD from three independent experiments. *P < 0.01, compared to DMSO groups.