EGF and glioblastoma: To investigate whether direct EGFR-PDGFRA receptor interaction may occur in glioblastoma cells we used co-immunopreciptation with/without EGF-stimulation to measure whether ligand-induced heterodimerization occurred in the co-amplified tumor sphere line TS753 (Fig. 2c), EGFR-amplified line TS600 (Fig. 2d and Supplementary Fig. 3a) and EGFRvIII-expressing line TS12017 (Supplementary Fig. S3b).