EGFR, also known as epidermal growth factor receptor, is a member of the ErbB family of receptors, a subfamily of four closely related receptor tyrosine kinase. This protein is type I transmembrane glycoprotein that binds a subset of EGF family ligands including EGF, amphiregulin, TGF-alpha, betacellulin, etc. It can also be recruited to form heterodimers with the ligand activated ErbB3 or ErbB4. EGFR signaling regulates multiple biological functions including cell proliferation, differentiation, motility, and apoptosis.