The EGFR (epidermal growth factor receptor) subfamily of receptor tyrosine kinases comprises four members: EGFR (also known as HER-1, ErbB1, or ErbB), ErbB2 (Neu, HER-2), ErbB3 (HER-3), and ErbB4 (HER-4). EGFR protein is type I transmembrane glycoprotein that binds a subset of EGF family ligands including EGF, amphiregulin, TGF-α, betacellulin, etc.The human EGFR cDNA encodes a 1210 amino acid (aa) precursor with a 24 aa signal peptide, a 621 aa extracellular domain (ECD), a 23 aa transmembrane segment, and a 542 aa cytoplasmic domain. EGFR signaling has been shown to exert action on carcinogenesis and disease progression, and thus EGFR protein is proposed as a target for cancer therapy currently, which is overexpressed in a wide variety of tumors and is the target of several anti-cancer drugs.