The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase of the ErbB family. Four members of the ErbB family have been identified: EGFR (ErbB1, HER1), ErbB2 (HER2), ErbB3 (HER3) and ErbB4 (HER4).
EGFR signaling is initiated by ligand binding to the extracellular ligand binding domain. This initiates receptor homo-/heterodimerization and autophosphorylation by the intracellular kinase domain, resulting in receptor activation. Following activation, phosphorylation of cytoplasmic substrates occurs and a signaling cascade is initiated that drives many cellular responses, including changes in gene expression, cytoskeletal rearrangement, decreased apoptosis and increased cell proliferation.