PDGFRA and glioblastoma: TCGA analyses revealed that GBM cases harboring concurrent EGFR amplification and PDGFRA mutations are exceedingly rare [18], and tumor cells in vitro exhibit increased apoptosis due to extracellular signal-regulated kinase (ERK) hyperactivation [26]; these findings suggest that single RTK activation is sufficient to promote cell proliferation, whereas additional mutations may induce cytotoxicity.