PTGS2 and carcinoma: There is little information about the elements involved in the regulation of COX-1 gene expression, but it has been reported that COX-1 can be co-induced with COX-2 in inflammatory joint fluid and in carcinoma.8,15,17,25 In many tissues, COX-2 cannot be detected, but its expression can be induced by various stimuli due to inflammation in monocytes or mast cells.