EREG is a ligand of the epidermal growth factor receptor (EGFR) and the structurally related erb-b2 receptor tyrosine kinase 4 (ERBB4), which stimulates tyrosine phosphorylation of EGFR and ERBB4. EREG may be involved in a wide range of biological processes including inflammation, wound healing, oocyte maturation, and cell proliferation. Additionally, EREG may promote the progression of cancers of various human tissue.