PTGS2 and colorectal cancer: However, COX-2, often referred to as the inducible or rate-limiting isoform, is usually undetectable in most normal tissues, being responsible for most of the prostanoid production during inflammation and markedly upregulated in various types of cancer, as well as in other diseases [1, 17, 31]. COX-2 gene can also be constitutively expressed in some tissues, such as the endothelium, kidney, gastrointestinal mucosa, and brain [32–34], and the constitutive expression of COX-2 gene may be a contributing factor promoting tumoral pathologies, such as colorectal cancer [35].