SOX2 and cancer: CSCs have been identified in human cancers based on various biomarkers, including cell surface molecules such as cluster of differentiation (CD) 44 and CD133, as well as by several pluripotent transcription factors, such as octamer-binding transcription factor 4 (Oct4), SEX-determining region (SRY) homology box 2 (Sox2), and Nanog, which also regulate their biological activities [58].