Chen et al. [61] recently demonstrated the existence of three different but coexisting types of glioma stem cells, which differ in CD133 expression: type 1 (CD133-negative cells able to generate CD133-positive progeny), type 2 (CD133-positive cells able to generate CD133-negative cells), and type 3 (CD133-negative which generate only CD133-negative progeny). This evidence concerns the gene PROM1 and central nervous system cancer.