EPGN (epigen) is an epithelial mitogen and EGFR ligand that promotes epithelial cell growth and proliferation. Unlike EGF, EPGN acts as a partial agonist of EGFR dimerization, stabilizing weaker and less stable EGFR dimeric conformations 1. Despite reduced dimerization strength, EPGN paradoxically induces more sustained EGFR signaling than EGF, eliciting differentiation rather than proliferation responses in breast cancer cells 1. EPGN activates downstream signaling cascades including MAPK phosphorylation and promotes positive regulation of the EGFR signaling pathway and mitotic nuclear division. Clinically, EPGN expression is dysregulated in multiple malignancies. It is overexpressed in transitional cell carcinoma of the bladder 2 and upregulated in common cutaneous warts induced by human papillomavirus 3. Beyond cancer, EPGN plays protective roles in mucosal defense: recombinant EPGN suppresses epithelial cell extrusion during mucosal damage, reducing fungal invasion and enhancing survival against opportunistic infections 4. EPGN has also been identified as a prognostic marker in machine learning models predicting melanoma survival and immunotherapy response 5. These diverse functions suggest EPGN's importance in epithelial homeostasis, immune response, and pathogenic resistance.