Human TGF alpha Carrier-Free Recombinant Protein, eBioscience?. Transforming growth factor (TGF) alpha is a 50-aa single-chain polypeptide derived from cleavage of transmembrane pro-TGF alpha. Sharing 42% identity with epidermal growth factor (EGF), TGF alpha binds the EGF receptor and activates downstream signaling pathways. TGF alpha is expressed by activated macrophages, keratinocytes, epithelial cells, and a variety of tumor-derived and transformed cell lines. This growth factor mediates cell proliferation and migration, as well as cellular transformation. Overexpression of TGF alpha has been linked to a variety of cancers, including the breast, colon, and stomach.