Mammospheres or breast cancer cells in hypoxia have higher expression of the KLF4, NANOG, OCT4, and SOX2 genes and CD44 and CD24, which encode pluripotency factors that are required for the maintenance of cancer stem cells, embryonic stem cells, and induced pluripotent stem cells [33,34,35,36]. The gene discussed is POU5F1; the disease is cancer.