GFAP and glioblastoma: In mRNA extracts of CD133+ vs CD133− cells from 13 GBM patients we also compared the expression of other genes characteristics of neural and glioma cancer stem cells and their progenitors, such as nestin, and the markers for more differentiated cells, such as glial fibrillar acidic protein (GFAP) indicating astrocyte lineage differentiation, and β-tubulin 3 (β-TUB 3), the marker of neural differentiation.