SOX2 and esophageal squamous cell carcinoma: The increased SOX2 expression observed in ESCC seems to be relevant for the development of this tumor since: (a) SOX2 is mutated in esophageal malformations and its expression is required for normal esophageal squamous development; (b) SOX2 expression is required for proliferation and anchorage-independent growth of ESCC lines; (c) SOX2 cooperates with FGFR2 to induce squamous tumor formation in immortalized tracheobronchial epithelial cells [52].