Nutlin‐3 acts as a DNA methyltransferase inhibitor to sensitize esophageal cancer to chemoradiation

Abstract Esophageal squamous cell carcinoma (ESCC) is highly resistant to chemoradiation therapy. We aimed to examine whether Nutlin‐3, a molecule that suppresses murine double min 2 (MDM2)‐mediated p53 and Retinoblastoma (RB) protein degradation leading to downregulation of DNA methyltransferases (DNMTs), can be a novel therapeutic agent for ESCC. We used wild‐type and chemoradiation‐resistant ESCC cell lines in this study. The expression of DNMTs, p53 and RB, and methylation level of tumor suppressor genes (TSG) were analyzed upon Nutlin‐3 treatment. The antitumor efficacy of Nutlin‐3 was investigated in ESCC cell lines and xenograft tumor model. TSG protein expression was checked in the excised tumor tissue. Nutlin‐3 induced upregulation of p53 and RB and downregulation of DNMTs proteins in the chemoradiation‐resistant and aggressive ESCC cells. The methylation level of TSGs was decreased by Nutlin‐3. Nutlin‐3 inhibits clonogenic growth of ESCC cells and exerts a synergistic cytotoxic‐effect when combined with chemotherapeutic agent cisplatin. Moreover, xenograft tumor growth in SCID mice was suppressed by Nutlin‐3. The protein expression level of DNMTs was downregulated, and that of TSGs was upregulated by Nutlin‐3 treatment in the excised tumor tissue. In conclusion, Nutlin‐3 is a potential therapeutic agent that can potentiate the treatment efficacy of chemoradiation‐resistant ESCC.