Abstract: The present invention is directed to a family of heparin-binding epithelial cell growth factors termed amphiregulins (AR). In particular, it relates to the isolation of AR genes from different animal species, expression of the genes, identification of various forms of biologically active AR products, purification of the AR products, antibodies specific for AR, and uses of AR. AR is detectable in several normal human epithelial cells and in a high percentage of human colon cancers. In addition to stimulating the growth of these cultured epithelial cells, AR may have a wide range of applications including, but not limited to, accelerating the growth of normal epithelial cells. In some tumor cell lines, primarily of breast or ovarian carcinomas, AR serves as a direct growth inhibitor. On the other hand, AR may function as a growth stimulatory molecule in colorectal carcinomas and other pathologies of increased epithelial proliferation.