HCPT enhances colon cancer cells to 5-FU-induced apoptosis. (A). The combination of 10-hydroxycamptothecin (HCPT) and 5-fluorouracil (5-FU) synergistically induces apoptosis. SW1116 cells and Colo 205 cells were treated with HCPT (2.5 μg/mL) or 5-FU (5 μg/mL) alone or in their combination for 48 hours. Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. (B-C) The combination of HCPT and 5-FU synergistically downregulates expression of X-linked inhibitor of apoptosis protein (XIAP) and survivin. SW1116 cells were treated with HCPT or 5-FU alone or in their combination for 48 hours. The mRNA expression of survivin (B) and XIAP (C) were determined by real-time PCR. The data are the mean ± SD of three independent experiments. *P < 0.05, compared to 5-FU or HCPT alone; #P < 0.01, compared to PBS.