In contrast to NSC scRNA‐seq studies where established cell‐based markers are used to enrich for NSCs (e.g., GLAST+/Prom1+) (Llorens‐Bobadilla et al, 2015), there are no pre‐existing universal markers for glioblastoma (GBM) tumor cells that can neatly resolve subpopulations into quiescent, "primed", G1, or differentiated cellular states (Lathia et al, 2015). This evidence concerns the gene PROM1 and glioblastoma.