TCHP and colorectal carcinoma: PGE2 is the prostanoid most involved in colorectal tumourigenesis.10 Several studies have reported that PGE2 and/or COX-2 levels are significantly higher in adenoma and CRC than in healthy tissue.11,12 In contrast, 15-hydroperoxyPGDH acts as a tumor suppressor protein, and its expression is downregulated in CRC cells, and restoration of 15-hydroperoxyPGDH expression exerts an antitumour effect.6,13 Many mechanisms have been proposed to explain the protumour role of PGE2.