PROM1 and glioblastoma: Other recent observations indicate that the expression of EGFRvIII seems to be related to cancer stem cells, as suggested by the observation that EGFRvIII is coexpressed with CD133 and defines the subset of glioblastoma cells with the highest tumor-initiating-capacity: the elimination of this subpopulation from the tumor greatly reduced the tumorigenicity of the implanted tumor [26].