SOX2 and breast cancer: In the present study, OCT4&SOX2 CTLs were hypothesized to exhibit good cytotoxic activity against BCSCs, based on the following observations: i) The expression of OCT4 and SOX2 was found to be associated with poor differentiation and worse prognosis in patients with breast cancer; ii) OCT4 and SOX2 were reported to be valuable markers of CSCs, including BCSCs; iii) targeting OCT4 and SOX2 resulted in anti-tumor effects towards CSCs, and iv) a previous study demonstrated that OCT&SOX2 CTLs effectively target and destroy lung cancer stem cells.