POU5F1 and cancer: Among the transcription factors described as regulators of pluripotency and maintenance of CSCs is the octamer-binding protein 4 (OCT4; also known as POU domain, class 5, transcription factor 1 (POU5F1)), an oncofetal protein that promotes self-renewal and maintenance of pluripotency of embryonic stem cells and induced stem cells, and which has been found to be involved in the progression and poor prognosis of various cancers [7], including gastric [8,9,10], pancreatic [11], breast [12], bladder [13], ovarian [14], prostate [15], and hepatocellular carcinoma [16].