Fig. 1.

a Epidermal growth factor receptor (EGFR) family and its targeting molecules. All the members in EGFR family have an extracellular domain (ECD), a transmembrane domain, and an intracellular domain. HER2 is the one member that does not have a natural ligand for the ECD, and tends to form a dimer with other members. With some ligand binding in the ECD of either member in the former dimer, the inner kinase pathway may be activated, which will promote cell proliferation and angiogenesis. b Expression levels of EGFR and HER2 in various breast and ovarian cancer cells. c Current clinical diagnostic methods for patient selection. IHC immunohistochemistry