EREG and neoplasm: We found that Hbegf as well as two additional EGFR ligands, amphiregulin (Areg) and epiregulin (Ereg), were specifically upregulated in epithelial cell adhesion molecule (EPCAM)-positive (EpCAM+) lung epithelial cells isolated from tumor-bearing lungs compared to healthy control lungs, and that erlotinib-induced tumor regression restored ligand expression to the levels in healthy lungs (Fig. 3A).