SOX2 is required for stem cell maintenance in the central nervous system, and it also regulates gene expression in the stomach. SOX2 is necessary for regulating multiple transcription factors that affect Oct 3/4 expression. An essential function of SOX2 is to stabilize embryonic stem cells in a pluripotent state by maintaining the requisite level of Oct 3/4 expression. Reportedly, SOX2 is associated with aggressive phenotypes of breast, head and neck, gastric, colorectal, bladder, and small cell lung cancers. However, SOX2 is expressed in a high percentage of lung squamous cell carcinomas and has been shown to be an independent favorable prognostic marker.