부산대학교 도서관

Background: TGFβ overproduction in cancer cells is one of the main characteristics of late tumor progression being implicated in metastasis, tumor growth, angiogenesis and immune response. We investigated the therapeutic efficacy of anti-TGFβ peptides in the control of angiogenesis elicited by conditional over-expression of TGFβ. Methods: We have inserted in human MCF7 mammary-cancer cells a mutated TGFβ gene in a tetracycline-repressible vector to obtain conditional expression of mature TGFβ upon transient transfection, evaluated the signaling pathways involved in TGFβ-dependent endothelial cells activation and the efficacy of anti-TGFβ peptides in the control of MCF7-TGFβ-dependent angiogenesis. Results: TGFβ over-expression induced in MCF7 several markers of the epithelial-to-mesenchymal transition. Conditioned-medium of TGFβ-transfected MCF7 stimulated angiogenesis in vivo and in vitro by subsequent activation of SMAD2/3 and SMAD1/5 signaling in endothelial cells, as well as SMAD4 nuclear translocation, resulting in over-expression of the proangiogenic growth and differentiation factor-5 (GDF5). Inhibition or silencing of GDF5 in TGFβ-stimulated EC resulted in impairment of GDF5 expression and of TGFβ-dependent urokinase-plasminogen activator receptor (uPAR) overproduction, leading to angiogenesis impairment. Two different TGFβ antagonist peptides inhibited all the angiogenesis-related properties elicited in EC by exogenous and conditionally-expressed TGFβ in vivo and in vitro, including SMAD1/5 phosphorylation, SMAD4 nuclear translocation, GDF5 and uPAR overexpression. Antagonist peptides and anti-GDF5 antibodies efficiently inhibited in vitro and in vivo angiogenesis. Conclusions: TGFβ produced by breast cancer cells induces in endothelial cells expression of GDF5, which in turn stimulates angiogenesis both in vitro and in vivo. Angiogenesis activation is rapid and the involved mechanism is totally opposed to the old and controversial dogma about the AKL5/ALK1 balance. The GDF-dependent pro-angiogenic effects of TGFβ are controlled by anti-TGFβ peptides and anti-GDF5 antibodies, providing a basis to develop targeted clinical studies. [ABSTRACT FROM AUTHOR]