PTGS2 and colorectal carcinoma: Furthermore, 5-ASA has been proposed as a preventive measure for CRC through the downregulation of cyclooxygenase-2 (COX-2) and inhibiting activation of transcription of nuclear factor kB (NF-kB) and phospholipase D. Indeed, several retrospective case-control studies found a significant protective effect of 5-ASA in UC, especially with doses >1.2 g/day.