Effects of PPD and 5-FU on cell death in two human colorectal cancer cell lines. (A) Effects of PPD (10–50 μM) on HCT-116 and SW-480 cell death. (B) Effects of 5-FU (10–100 μM) on HCT-116 and SW-480 cell death. Cell death in the presence of PPD or 5-FU was measured after 48 h treatment. Data are presented as the mean ± standard error. *P < 0.05, **P < 0.01 vs. control.