POU5F1 and breast cancer: To further investigate the association of OCT4 with normal and aberrant breast development, we compared expression of OCT4 and associated ESC genes between hESCs and normal self-renewing stem cells accessed via breastmilk (hBSCs) or available OCT4-overexpressing breast cancer cell line models (OCT4-overexpressing tumorigenic breast cell lines, OTBCs) possessing tumor-initiating features.