Transforming growth factor alpha (TGF-α), also known as TCGF and MDGF-2, is an acid- and heat-stable protein and member of the EGF family of cytokines. It is thought to be the major autocrine factor controlling growth in epidermal cells (1). TGF-α plays an important role in cell proliferation during embryogenesis and stimulates neural cell proliferation in the adult injured brain (2). It is produced by monocytes, keratinocytes, and various tumor cells. TGF-α binds to the EGF receptor, mediating tyrosine phosphorylation of the receptor, and promotes cell-cell adhesion and to cell-cell stimulation (1). It is probably involved in the regeneration of liver tissues (3) and also affects bone formation/remodeling by inhibition of the synthesis of collagen and release of calcium. It has been suggested that TGF-α may act as an autocrine growth factor for the induction or maintenance of malignancy. It is present in high levels in around half of all breast tumors, and these tumors tend to be more aggressive and more likely to spread to the lungs (4). It has been shown that TGF-α can prompt breast cancer cells to make another cytokine called angiopoietin-like 4 (ANGPTL4), which helps the cells to spread through the bloodstream (5). Human, murine and rat TGF-α are cross-species reactive.

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