BMI1 and glioblastoma: Initially, the phenotypic characterization of GBM CSCs was based on the recognition of distinctive NSC markers, such as nestin, Sox2, Nanog, Oct4, BMI1, musashi-1, but later on, components of pathways active in brain development were found to be expressed in GBM CSCs, including Notch (Wang et al., 2010a), Wnt (Jin et al., 2011), bone morphogenetic protein (BMP; Piccirillo et al., 2006) and TGF-β (Ikushima et al., 2009).