HBEGF and cancer: ADAM17 proteolytically cleaves and activates several EGFR ligands such as epiregulin, transforming growth factor alpha (TGF-alpha), amphiregulin (AREG) and heparin-binding EGF-like growth factor (HB-EGF) and may thus contribute to cancer progression through EGFR activation [12,14,18,19,20,21].