IGF1 and neoplasm: It is postulated that cytokines and growth factors produced by the GBM tumor microenvironment, including stromal cell‐derived factor 1 (SDF‐1), monocyte chemotactic protein 1 (MCP1), insulin‐like growth factor 1 (IGF1), and vascular endothelial growth factor (VEGF), act as chemoattractants that induce NSC tumor‐homing.35, 36, 37