GLI1 and colorectal cancer: Using Gli-dependent luciferase reporter activity as a Hh activity readout, we observed that PGE2 profoundly increased the Gli activity in multiple colorectal cancer cell lines, including LS174T, SW480, SW620, and DLD-1 cells (Fig. 1A), in a time-dependent manner, reaching maximum at about 6 h (Fig. 1B).