CDKN2A and esophageal squamous cell carcinoma: Aberrant DNA hypermethylation of promoter regions in the tumor suppressor genes p16 and p53 was reported to be responsible for the silence and inactivation of the corresponding gene which is involved in carcinogenesis of esophagus [9, 31–35], suggesting that epigenetic alteration in p16 and p53 is involved in the pathogenesis of ESCC.