The EGF Receptor (EGFR) is one of the four members of the EGFR subfamily of receptor tyrosine kinases. It is a transmembrane glycoprotein expressed on the cell surface and is a receptor for EGF and at least six other structurally related ligands including amphiregulin, betacellulin and TGF-alpha. Binding of EGFR to one of these ligands induces receptor dimerization and tyrosine autophosphorylation, leading to cell proliferation. It is involved in regulation of other functions including differentiation, survival, motility and apoptosis. EGFR has been found to be overexpressed in many tumors.