PTGS2 and colorectal adenoma: We propose that epithelial cell Cox-2-expression in our cLys-Cox-2 x ApcMin/+ mouse model is analogous to the switch to epithelial cell COX-2 protein expression in human colorectal adenomas that exhibit ‘advanced’ features (increased size, high-grade dysplasia, villous architecture) associated with tumour progression to cancer11, 47, 48.