Xenograft tumors generated from FACS-sorted CD133+ human GBM cells in NOD.SCID mice showed GPR133 immunoreactivity overlapping with hypoxyprobe (pimonidazole) staining, which identified hypoxic regions within poorly perfused regions of the tumor, as analyzed by intravenously injected Evans Blue34 (Supplementary Figures 3bi–iii). The gene discussed is PROM1; the disease is glioblastoma.