In the case of mesenchymal gliomas, all three Id proteins, Id1-3, are required for maintaining high-grade gliomas, whereas deletion of these three genes leads to tumor regression through release of glioma initiating cells (GICs) from the perivascular tumor niche, which is mediated by the inhibition of the master regulator of cell adhesion Rap1. The gene discussed is ID1; the disease is central nervous system cancer.