Transforming growth factors beta.

Since its discovery as a factor able to induce phenotypic transformation with transforming growth factor alpha, transforming growth factor beta (TGF beta) has been found to have unexpectedly widespread and frequently, seemingly paradoxical effects on a variety of cell types. Thus, a significant property of TGF beta activity is the ability to inhibit cellular growth and transformation. More recently, further important potential roles have also been found for TGF beta including the control of embryonal development, cellular differentiation, hormone secretion and immune function. Multiple forms of both TGF beta and TGF beta receptors are now known to exist, which may generate a complex and diverse range of interacting signals. The multifunctional actions of the TGF beta family are frequently defined in concert with other extracellular factors and much still has to be understood concerning these synergistic processes.