CD133 which is encoded by the prominin-1 (PROM1) gene is well known as a marker of cancer stemness, and more so in GBM, where it has been shown to be essential for GSC maintenance, serving as a marker of cells with enhanced capacity for neurosphere growth initiation and formation of heterogeneous tumors in xenograft glioma mice models [34]. The gene discussed is PROM1; the disease is glioblastoma.