Figure 6: TGF-β and uPA system cooperation during the induction of epithelial to mesenchymal transition. Both TGF-β and uPA/uPAR are involved in the induction of EMT, and mutual cooperation may be operating, since TGF-β stimulates the expression of uPA and uPAR in cancer cells, and the enhancement of uPA levels increased the activation of plasmin, which in turn activated extracellular matrix-associated latent complex, thus, exacerbating TGF-β-induced EMT. Meanwhile, the increment of uPA-uPAR also stimulates EMT, and both finally may collaborate to the induction of the epithelial conversion to the mesenchymal phenotype, thus, strengthening the cancer cell invasion and metastasis.