To further examine differences in expression of OCT4 and associated ESC TFs between normal lactating breast stem cells and breast CSCs, we took advantage of breastmilk as a source of stem cells from the normal lactating breast, and of OCT4-overexpressing breast cancer cell line models (OTBCs), given that cell lines isolated from tumors that have high OCT4 expression are not commercially available. This evidence concerns the gene POU5F1 and breast cancer.