PTGER4 and colorectal carcinoma: PGE2 reportedly promotes tumour epithelial cell proliferation, survival and migration/invasion via multiple signalling pathways.6–8 Wang and co-workers9 suggested that PGE2 promotes CRC initiation, growth and metastasis via CSCs, and that PTGER4 mediates the effects of PGE2 on the induction of colonic CSC expansion and promotion of liver metastasis.