DLL3 and central nervous system cancer: Some specific notable gene expression differences included: epidermal growth factor receptor (EGFR) was only highly expressed in the human PDGFRA-overexpressing tumors; early growth response 1 (EGR1) expression was only increased in human and canine tumors, hypoxia-inducible factor 1-α (HIF1A), delta-like canonical notch ligand 3 (DLL3), cytotoxic T-lymphocyte associated protein 4 (CTLA4), and tumor necrosis factor receptor superfamily 12 A (TNFRSF12 A), also known as fibroblast growth factor inducible 14 (Fn14), were not differentially expressed in canine gliomas.