POU5F1 and cancer: For instance, Oct4 maintains the pluripotent state of embryonic stem cells during preimplantation development, but its activation results in dysplastic growths in epithelial tissues with the expansion of progenitor cells and inhibition of differentiation (Hochedlinger et al., 2005) while blocking Oct4 expression leads to apoptosis of CSC populations in human and murine cancer cell lines (Hu et al., 2008).