EGFR is known to bind ligands including epidermal growth factor (EGF), transforming growth factor-?? (TGf-??), amphiregulin, heparin-binding EGF (hb-EGF), betacellulin, and epiregulin (Herbst and Shin, Cancer 94:1593-1611 (2002); Mendelsohn and Baselga, Oncogene 19:6550-6565 (2000)).