DKK1 and osteosarcoma: For example, it was reported that SOX2 antagonizes the WNT signaling to inhibit the differentiation of adult stem cells (ASCs) [42] and osteoblast lineage [43] and enhance the tumorigenesis and self renewal property of osteosarcomas [44] by promoting the transcription of negative regulator of WNT signaling, such as DKK1, APC and GSK3β.