Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that regulates proliferation, migration, differentiation, and survival of many different cell types. Deletion or mutation of different members of the TGF-β family have been shown to cause vascular remodeling defect and absence of mural cell formation, leading to embryonic lethality or severe vascular disorders. TGF-β induces smooth muscle differentiation via Notch or SMAD2 and SMAD3 signaling in ES cells or in a neural crest stem cell line. TGF-β binds to TGF-βRI and to induce phosphorylation of SMAD2/3, thereby inhibiting proliferation, tube formation, and migration of endothelial cells (ECs).

TGF-β is a pluripotent cytokine with dual tumour-suppressive and tumour-promoting effects. TGF-β induces the epithelial-to-mesenchymal transition (EMT) leading to increased cell plasticity at the onset of cancer cell invasion and metastasis.