EGFR is a transmembrane glycoprotein that is one of four members of the ErbB family of tyrosine kinase receptors. Activation of EGFR leads to autophosphorylation of the receptor tyrosine kinase, which initiates downstream signaling cascades involved in the regulation of cell proliferation, differentiation, and survival. The abnormal activation of EGFR through a variety of mechanisms, such as receptor overexpression, mutation, ligand-dependent receptor dimerization, ligand-independent activation, is associated with the occurrence and development of a variety of human tumors. Inhibition of EGFR is one of the key targets of cancer chemotherapy.