POU5F1 and cancer: Octamer-binding transcription factor 4 (OCT4), is considered as a putative cancer stem cells (CSCs) marker, which is a member of the Pit-Oct-Unc (POU) transcription factor family, mediating tumor proliferation and differentiation, abnormally expressed in bladder cancer, non-small cell lung cancer, cervical cancer and other cancers [8–13].