CDK4 and neoplasm: Higher expression levels for the EGFR, PDGFRA, CDK4, and MDM4 genes in GBM tumor vs. normal brain tissues was further confirmed in those 264 primary GBM vs. 29 normal brain tissue samples from the GEO database with median FC values of 4.5, 4.4, 2.7, and 2.0 for the EGFR, CDK4, MDM4, and PDGFRA genes in the tumor vs. normal brain samples, respectively (Table 1).