Transforming growth factor ? (TGF ?) is a pleiotropic cytokine that exhibits a broad spectrum of biological and regulatory effects on the cellular and organism level. It plays a critical role in cellular growth, development, differentiation, proliferation, extracellular matrix (ECM) synthesis and degradation, control of mesenchymal-epithelial interactions during embryogenesis, immune modulation, apoptosis, cell cycle progression, angiogenesis, adhesion and migration and leukocyte chemotaxis. It has both tumor suppressive and tumor promoting activities and is highly regulated at all levels (e.g. mRNA turnover, latent protein activation or post-translational modifications).