Aberrant DNA methylation contributes to the development of radioresistance during anticancer therapy; for example, high methylation of death-associated protein kinase (DAPK) [155], CHFR [156] and FGF5 [157] is associated with a diminished response to CRT in ESCC, in which DNA methyltransferases (DNMTs) play an important role, including DNMT1, DNMT3A and DNMT3B. The gene discussed is DNMT1; the disease is esophageal squamous cell carcinoma.