POU5F1 and cancer: CSCs drive cancer initiation, progression, metastasis, recurrence and drug resistance (Chen et al., 2013), and express Nanog, CD133, CD90, SOX2, EpCAM, CD44, Klf4 and Oct4, some of which may functionally support liver CSC phenotypes like invasiveness and chemoresistance (Yamashita and Wang, 2013).