COX2 (Cyclooxygenase 2) is an inducible enzyme. It is involved in the response of cells to growth factors, tumor promoters, and cytokines that induce its expression. Given its role in synthesizing prostaglandins, COX2 is therefore of interest in studying immune response regulation. COX2 is induced by a wide variety of stimuli and was initially identified as immediate early growth response gene. In addition, COX2 expression markedly increased in 85-90% of human colorectal adenocarcinoma whereas COX1 levels remain unchanged.