PTGS2 and colorectal carcinoma: The observations that EGFR activity is increased in a PTGS2 (COX-2) transgenic mouse and forced expression of PTGS2 (COX-2) in human CRC cells stimulates cellular proliferation through induction of EGFR [31,75] indicate that EGFR is a downstream target of PTGS2 (COX-2).