TP53 and esophageal squamous cell carcinoma: RNF6 is first reported as a tumor suppressor gene not only because RNF6 is mapped to chromosome 13q12 [3], a location harboring several other suppressor genes such as p53 and PTEN, but also because its mutations are found in the gene of RNF6 in esophageal squamous cell carcinoma [4].