EGF: Epidermal growth factor. A polypeptide (small protein) that is a powerful mitogen. (It stimulates cells to enter mitosis, cell division. ) EGF promotes cell growth and differentiation, is essential in embryogenesis, and is important in wound healing. It is produced by many normal cell types and is made in large amounts by some tumors. The EGF gene is on chromosome 4q25 (whereas the gene for its receptor, EGFR, is on chromosome 7). The kidney is the main source of circulating EGF. EGF is also known as urogastrone (URG).