SOX2 and breast cancer: SOX2, a protein initially is known as a regulator of self-renewal in mouse and human embryonic stem cells, as well function as a key transcription factor to induce pluripotent stem cells from fibroblast cells.29 Mounting evidence suggests that SOX2 is a critical biomarker of self-renewal and maintains the stemness of CSCs in types of cancer, including breast cancer, osteosarcomas and glioma.30