GFAP and glioblastoma: Consistent with previously published data (Fael Al-Mayhani et al., 2009), primary glioblastoma cells cultured as non-adherent neurospheres in serum-free medium expressed high levels of stem cell markers including CD133, nestin and Sox2 (Fig. 1A, supplementary Fig. S1A,B), low levels of astrocytic differentiation markers including GFAP (supplementary Fig. S1B) and generated invasive intracranial xenografts in CD1 nude mice.