The anti-CSC activity of AD-01 led to downregulation of stem cell markers, Nanog, Oct4 and Sox2 in breast cancer cell lines while the intratumoural knockdown of FKBPL in a ZR-75 breast cancer xenograft mouse model increased the expression of Nanog/, Oct4 and Sox2 [5]; Sox2 has been implicated in both metastasis and endocrine therapy resistance [28–30]. This evidence concerns the gene POU5F1 and breast cancer.