Transforming growth factor-beta: recent progress and new challenges.

Abstract

I T is just 10 years since the peptide, transforming growth factor-/31 (TGF-~I) 1, was isolated from human platelets, human placenta, and bovine kidney and characterized as a discrete molecular entity, namely a 25-kD homodimer with a unique NH2-terminal sequence. Two years later this molecule was cloned, and subsequently four other closely related isoforms have been found in vertebrates; three isoforms (TGF-~s 1, 2, and 3) are known in man. TGF-~ can now be considered the prototype of a multifunctional cytokine, especially after the discovery that it could act both as an inhibitor and stimulator of cell replication, as well as control the synthesis of many of the components of the extracellular matrix (for reviews of the above see Roberts and Sporn, 1990; Massagu6, 1990; Moses et al., 1990; Sporn and Roberts, 1990). There has been immense progress in TGF-/~ research in the past two years. This mini-review will highlight some of these accomplishraents and indicate a few challenges for the future. We will confine this brief review to the TGF-/3s themselves and will not consider the extended TGF-B family, which includes the inhibins, activins, bone morphogenetic proteins, and related morphogenetic peptides, all of which are of increasing importance in many areas of cell biology, such as reproduction and development.