DNMT1 and esophageal squamous cell carcinoma: Nutlin-3, a murine double min 2 (MDM2) small molecule inhibitor, upregulated tumor suppressor gene p53 and RB levels in ESCC cells, thereby inhibiting the expression of the three isoforms of DNMT, and reduce methylation levels of multiple tumor suppressor genes, and increased radiosensitivity of ESCC [160].