MDM2 and esophageal squamous cell carcinoma: Overexpression of MDM2, for instance, has been observed in many types of cancers, particularly in cancers where p53 mutations are less frequent including breast cancer, prostate cancer, colorectal adenocarcinoma, esophageal squamous cell carcinoma, gastric cancer and non-small cell lung cancer, and high MDM2 levels are associated with poor prognosis of patients [228,229,230,231,232,233,234].