The three mammalian isoforms of TGF-beta, TGF-beta1, beta2, beta3, signal through the same receptor and elicit similar biological responses.They are multifunctional cytokines that regulate cell proliferation, growth, differentiation and motility as well as synthesis and deposition of the extracellular matrix.They are involved in various physiological processes including embryogenesis, tissue remodeling and wound healing.They are secreted predominantly as latent complexes which are stored at the cell surface and in the extracellular matrix.The release of biologically active TGF-beta isoform from a latent complex involves proteolytic processing of the complex and /or induction of conformational changes by proteins such as thrombospondin-1.TGF-beta1 is the most abundant isoform secreted by almost every cell type.It was originally identified for its ability to induce phenotypic transformation of fibroblasts and recently it has been implicated in the formation of skin tumors.Human TGF-beta1 is a 25.0kD protein with each subunit containing 112 amino acid residues, linked by a single disulfide bond.