PTGS2 and neoplasm: The hypermethylation of COX-2 gene by histone deacetylation has been described in several tumor types such as gastric [95], pancreatic [96], breast [97, 98], hepatic [99–101], nasopharyngeal [102], prostate [103, 104], esophageal [105, 106], and cervical tumors [107, 108].