POU5F1 and sarcoma: Our previous study showed the key role of the pluripotency factor SOX2 in sarcoma tumorigenesis [5]; thus, we aimed to investigate whether the enrichment of CSCs during serial xenotransplantation was accompanied by changes in expression of the core pluripotency factors (SOX2, OCT4, and NANOG) or commonly used CSC markers (nestin, CD133, and ABCG2).