These findings denote that physiologically relevant levels of BPA increase growth of ER-positive breast cancer through stem-like cell activity via upregulation of SOX2, which participates among other factors [e.g., octamer-binding transcription factor-4 (OCT4)] in the maintenance of pluripotency of breast stem cells and an undifferentiated cellular state (39). This evidence concerns the gene POU5F1 and breast cancer.