CXCR4 and glioblastoma: Enriched pathways also included inhibitor of differentiation 1 (ID1) signaling, which is linked to glioma invasion and suppression of differentiation of GBM stem cells29, CDK5 signaling, a well-established regulator of neural progenitor migration30 and associated with GBM invasion31, and CXCR4 signaling, which emphasizes a migratory response of glioma cells to hypoxia32 (Fig. 3B).