POU5F1 and osteosarcoma: Conventional chemotherapeutic drugs such as doxorubicin, cisplatin and methotrexate, effectively induce the expression of stem cells markers (i.e., SOX2, OCT4, KLF4 or Nanog) and multidrug resistance-related transporters (i.e., ABCG2 or ABCB1) in osteosarcoma cells through the activation of the Wnt/β-Cat pathway [62].