EGFR and glioblastoma: Based on gene expression patterns, somatic mutations, and DNA copy number, the GBM subtypes were clustered into three major subpopulations (proneural (PN), classical (CL), and mesenchymal (MES)) guided by three key oncogenes—platelet growth factor receptor-α (PDGFRA) activation, epidermal growth factor receptor (EGFR) activation, and tumor suppressor neurofibromin 1 (NF1) deletions, respectively.