PTGS2 and colorectal carcinoma: While some studies have linked high COX-2 expression to worse outcomes in CRC (Soumaoro et al., 2004; Ogino et al., 2008; Wang and Dubois, 2010), there is a subset of gastric cancers and CRCs where the expression of COX-2 is lost through hypermethylation of the promoter (Toyota et al., 2000; Song et al., 2001; Kikuchi et al., 2002; Hur et al., 2003).