The Pit-Oct-Unc (POU) homeodomain transcription factor, POU5F1 (also known as OCT-3, OCT-4, and OCT 3/4), is a key regulator of self-renewal and differentiation in embryonic stem cells [12–15]. POU5F1 gene expresses in adult human stem cells, immortalized nontumorigenic cells, and tumor cells and cell lines, and its level decreases with the onset of differentiation and loss of pluripotency in these cells [16–18]. The gene discussed is POU5F1; the disease is neoplasm.