Norcantharidin (NCTD) substantially decreased the level of p‐ERK. (a) Western blotting for MAPK and p‐MAPK after various doses of NCTD (0, 20, 40, 60 μmol/L) on HT‐29 cells for 24, 36, and 48 h. (b,c) The level of p‐ERK decreased substantially with the addition of NCTD in a dose‐ and time‐dependent manner. Identical results were obtained in three independent experiments.