Transforming growth factors from neoplastic and nonneoplastic tissues.

Transforming growth factors (TGFs) are a heterogeneous family of polypeptides that induce anchorage-independent growth in nonneoplastic anchorage-dependent cells. They have been found in many tissues, both neoplastic and nonneoplastic. All TGFs isolated thus far are of low molecular weight (6000-25,000), are acid and heat stable, and are inactivated by reagents that reduce disulfide bonds. TGFs have been classified as type alpha or type beta based on their interactions with the receptor for epidermal growth factor (EGF) and their requirement for EGF (or an EGF-like polypeptide) for functional activity. TGF-alpha and TGF-beta act synergistically. TGF-alpha induces phosphorylation of tyrosine in the EGF receptor. TGF-beta, isolated from bovine sources, accelerates experimental wound healing in rats.