The power of the few

Converging evidence from numerous laboratories has revealed that malignant brain cancers are complex ecological systems composed of distinct cellular and acellular elements that collectively dictate glioblastoma biology. Our understanding of the individual contributions of each of these components is vital to the design of effective therapies against these cancers. In this issue of Genes & Development, Zanca and colleagues (pp. 1212–1227) demonstrate that one subpopulation of glioblastoma cells expressing a mutant epidermal growth factor receptor (EGFRvIII) is responsible for the survival of non-EGFRvIII-expressing tumor cells as well as for evading molecularly targeted therapy.