POU5F1 and neoplasm: During hypoxia, anaerobic conditions prevail within the tumor, activating oncogenes such as MYC and RAS, resulting in the expression of hypoxia inducible factor- (HIF-) 1 and HIF-2 and the induction of the expression of pluripotent genes, such as Oct4, Sox3, and kruppel-like factor- (KLF-) 4 [47, 57].