MPPE1 and colorectal cancer: Interestingly, key enzymes for PGE2 production such as COX-2 are often overexpressed in colorectal cancer and associated with poor prognosis (Dannenberg and Subbaramaiah, 2003), suggesting that PGE2 might be one of the mechanism responsible for the scarcity of cDC1 in the TME of some human tumors.