PRNP and glioblastoma: To confirm the role of PrPC as a stemness regulator of GBM CSCs, we investigated phenotype alterations induced by PrPC down-regulation, focusing on mRNA and protein levels of Sox2 and NANOG, two transcription factors essential for maintaining self-renewal and pluripotency, not only in human embryonic [54] and neural stem cells [55] but also in human GBM CSCs [56].