Epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein and member of the protein kinase superfamily that regulates cell growth and differentiation. EGFR binds EGF, TGF-alpha, amphiregulin, betacellulin, heparin-binding EGF-like growth factor, GP30, and vaccinia virus growth factor - all members of the EGF family. Ligand binding induces EGFR dimerization and autophosphorylation, initiating the MAPK, Akt, and JNK signaling pathways. EGFR is expressed by epithelial and endothelial cells and is frequently expressed by epithelial carcinomas.