TGF-alpha is an EGF-related polypeptide growth factor that signals through the EGF receptor, and stimulates the proliferation of a wide range of epidermal and epithelial cells. It is produced by monocytes, keratinocytes, and various tumor cells. TGF-alpha induces anchorage-independence transformation in cultured cells. Human, murine and rat TGF-alpha are cross-species reactive. Recombinant human TGF-alpha is a 50 amino acid polypeptide (5.5 kDa) which shares approximately 40% sequence homology with EGF, including 6 conserved cysteine residues, which form 3 intramolecular disulfide bonds.