Epigen is an EGF-related polypeptide growth factor that signals through the ErbB receptor-1. It is produced in several tissues, including the testis, liver, and heart, as well as in certain tumor cells. Epigen is mitogenic for fibroblasts and epithelial cells. Human Epigen is initially synthesized as a glycosylated 14.7 kDa transmembrane precursor protein, which is processed by proteolytic cleavage to produce a mature soluble sequence. Recombinant Human Epigen is a 7.9 kDa monomeric protein, containing 72 amino acid residues, which comprises the EGF-homologous portion of the Epigen precursor.