title: CD36-mediated activation of endothelial cell apoptosis by an N-terminal recombinant fragment of thrombospondin-2 inhibits breast cancer growth and metastasis in vivo.
abstract: Thus far the clinical benefits seen in breast cancer patients treated with drugs targeting the vascular endothelial growth factor (VEGF) pathway are only modest. Consequently, additional antiangiogenic approaches for treatment of breast cancer need to be investigated. Thrombospondin-2 (TSP-2) has been shown to inhibit tumor growth and angiogenesis with a greater potency than the related molecule TSP-1. The systemic effects of TSP-2 on tumor metastasis and the underlying molecular mechanisms of the antiangiogenic activity of TSP-2 have remained poorly understood. We generated a recombinant fusion protein consisting of the N-terminal region of TSP-2 and the IgG-Fc1 fragment (N-TSP2-Fc) and could demonstrate that the antiangiogenic activity of N-TSP2-Fc is dependent on the CD36 receptor. We found that N-TSP2-Fc inhibited VEGF-induced tube formation of human dermal microvascular endothelial cells (HDMEC) on matrigel in vitro and that concurrent incubation of anti-CD36 antibody with N-TSP2-Fc resulted in tube formation that was comparable to untreated control. N-TSP2-Fc potently induced apoptosis of HDMEC in vitro in a CD36-dependent manner. Moreover, we could demonstrate a CD36 receptor-mediated loss of mitochondrial membrane potential and activation of caspase-3 in HDMEC in vitro. Daily intraperitoneal injections of N-TSP2-Fc resulted in a significant inhibition of the growth of human MDA-MB-435 and MDA-MB-231 tumor cells grown in the mammary gland of immunodeficient nude mice and in reduced tumor vascularization. Finally, increased serum concentrations of N-TSP2-Fc significantly inhibited regional metastasis to lymph nodes and distant metastasis to lung as shown by quantitative real-time alu PCR. These results identify N-TSP2-Fc as a potent systemic inhibitor of tumor metastasis and provide strong evidence for an important role of the CD36 receptor in mediating the antiangiogenic activity of TSP-2.
authors: Institute for Oral and Musculoskeletal Biology, Department of Dermatology, Center for Biochemistry, Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, 50931 Cologne, Germany.
authors: Manuel
authors: M
authors: Koch
authors: Fadi
authors: F
authors: Hussein
authors: Andreas
authors: A
authors: Woeste
authors: Carsten
authors: C
authors: Gründker
authors: Karl
authors: K
authors: Frontzek
authors: Günter
authors: G
authors: Emons
authors: Thomas
authors: T
authors: Hawighorst
mesh_terms: D020533:Angiogenesis Inhibitors / Q000627:therapeutic use; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000098:blood supply / Q000473:pathology / Q000517:prevention & control*; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D020405:Dermis / Q000166:cytology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000098:blood supply / Q000517:prevention & control* / Q000556:secondary; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000517:prevention & control*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D019699:Thrombospondins / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D000099262:Thrombospondin 2
chemical_list: D020533:Angiogenesis Inhibitors; D018955:CD36 Antigens; D053148:Caspase 3; D011993:Recombinant Fusion Proteins; D019699:Thrombospondins; D042461:Vascular Endothelial Growth Factor A; D000099262:Thrombospondin 2