AREG (amphiregulin) is an EGFR ligand that functions as an autocrine and paracrine growth factor with diverse roles in immunity, tissue repair, and disease pathology 1. AREG activates EGFR signaling on multiple target cell types, including keratinocytes, hepatic stellate cells, fibroblasts, and immune cells, triggering downstream pathways such as ERK1/2, PI3K/AKT, and Hippo-YAP signaling 234. AREG is produced by diverse cell populations including regulatory T cells, innate lymphoid cells, mast cells, basophils, and cancer-associated fibroblasts 1546. In chr4 liver disease, Treg cell-derived AREG paradoxically promotes liver fibrosis and metabolic dysfunction via hepatic stellate cell EGFR signaling 4. In cancer contexts, AREG contributes to therapeutic resistance and metastatic progression—radiation-induced AREG reprograms myeloid cells toward immunosuppression 7, while fibroblast-derived AREG maintains cancer stem cell stemness in gastric cancer 6. Conversely, lung ILC-derived AREG promotes epithelial repair after influenza infection 5. In psoriasis, IL-17A drives AREG expression via YAP activation, promoting keratinocyte proliferation 3. Elevated serum AREG serves as a biomarker for persistent atrial fibrillation 8. These findings reveal AREG as a context-dependent regulator with both protective and pathogenic functions.