Activation of epidermal growth factor (EGF) receptor (EGFR) by EGF or truncation. Green arrows indicate signals. Based on a figure from Mellinghoff et al,¹¹⁸  and modified from Schlessinger.⁵⁹  Binding of EGF on normal EGF-R induces a conformational change that facilitates dimerization. Glioblastoma multiforme cells may circumvent EGF requirement by deletions in the ligand-binding domain of EGF-R, which promote receptor dimerization and activation.