POU5F1 and colorectal carcinoma: Although spheroidal cultures of colon cancer cells can still be heterogeneous in terms of clonogenicity and malignant potential, evidence for the (a) expression of CD133 in the majority of CSC-P cells, (b) downregulation of the pluripotency factors Nanog and Oct4 in differentiative culture conditions, and (c) constitutive activation of the Wnt pathway as revealed by the fluorescent reporter TopGFP clearly argues in favor of this cell model being representative of the CRC stem cell subset.