PROM1 and glioblastoma: To investigate whether Prom1+ endothelium is more important for proneural GBM subtype than Prom1− endothelium, we used fluorescence-activated cell sorting (FACS) to isolate GFP+ Prom1+ and GFP+ Prom1− endothelial cells from the brain of VEGFR2-GFP mice.