CDH1 and nasopharyngeal carcinoma: In fact, the promoter regions of several critical TSGs have been reported with hypermethylation and validated to be down-regulated in NPC including RASSF1 (26, 27), CDKN2A (28–30), MIPOL1 (31, 32), PTPRG (33, 34), RRAD (25, 35), THY1 (36, 37), PTEN (38, 39), CDH1 (40, 41), and RARβ2 (42, 43).