Abstract
Transforming growth factors (TGFs) isolated from murine sarcoma virus-transformed 3T3 cells have been separated by high-pressure liquid chromatography into two subsets. One subset, called TGFα, competes with epidermal growth factor (EGF) for receptor sites, whereas the other, called TGFβ, does not. TGBβ, purified by high-pressure liquid chromatography, will not induce formation of large colonies of cells in soft agar in the absence of TGFα or EGF. However, the combined action of either TGFα or EGF (which by themselves are relatively ineffective in promoting growth of cells in soft agar) together with TGFβ results in a potent synergistic effect, with formation of large colonies. Chemically modified analogs of EGF also potentiate TGFβ activity to the extent that they bind to the EGF receptor. It is suggested that TGFβ may be an important mediator of the known effects of both TGFα and EGF on neoplastic transformation.