AR and neoplasm: Thus, in addition to overexpression of the EGF receptor, its ligands epidermal growth factor (EGF), transforming growth factor-α TGF-α, amphiregulin (AR), betacellulin (BTC), heparin-binding EGF-like growth factor (HB-EGF), and epiregulin (EREG) have been reported to be upregulated in tumor tissues (9–15).