CDKN2A and esophageal squamous cell carcinoma: In this study, we attempted to investigate the gene-nutrition interaction with folate and aberrant DNA methylation in the different stages of carcinogenesis of ESCC by detecting serum folate level, promoter methylation status of frequently methylated tumor suppressor genes p16 and p53, and evaluating the intake frequency of foods rich in folate among healthy controls, EPL cases, and ESCC cases.