Scientists have shown for the first time that malignant brain tumors arise directly from brain stem cells. Overproduction of the protein Tlx in mice stimulates the development of malignant brain tumors from brain stem cells. Tlx also plays an important role in glioblastoma, the most malignant of human brain cancers. Therefore, the discovery of Tlx might provide the first target for a specific therapy against glioblastoma.