title: Monoclonal antibodies to murine thrombospondin-1 and thrombospondin-2 reveal differential expression patterns in cancer and low antigen expression in normal tissues.
abstract: There is a considerable interest for the discovery and characterization of tumor-associated antigens, which may facilitate antibody-based pharmacodelivery strategies. Thrombospondin-1 and thrombospondin-2 are homologous secreted proteins, which have previously been reported to be overexpressed during remodeling typical for wound healing and tumor progression and to possibly play a functional role in cell proliferation, migration and apoptosis. To our knowledge, a complete immunohistochemical characterization of thrombospondins levels in normal rodent tissues has not been reported so far. Using antibody phage technology, we have generated and characterized monoclonal antibodies specific to murine thrombospondin-1 and thrombospondin-2, two antigens which share 62% aminoacid identity. An immunofluorescence analysis revealed that both antigens are virtually undetectable in normal mouse tissues, except for a weak staining of heart tissue by antibodies specific to thrombospondin-1. The analysis also showed that thrombospondin-1 was strongly expressed in 5/7 human tumors xenografted in nude mice, while it was only barely detectable in 3/8 murine tumors grafted in immunocompetent mice. By contrast, a high-affinity antibody to thrombospondin-2 revealed a much lower level of expression of this antigen in cancer specimens. Our analysis resolves ambiguities related to conflicting reports on thrombosponding expression in health and disease. Based on our findings, thrombospondin-1 (and not thrombospondin-2) may be considered as a target for antibody-based pharmacodelivery strategies, in consideration of its low expression in normal tissues and its upregulation in cancer.
authors.affiliation: Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zürich), Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
authors.forename: Emil
authors.initials: E
authors.lastname: Bujak
authors.affiliation: Philochem AG, Libernstrasse 3, CH-8112 Otelfingen, Switzerland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Pretto
authors.affiliation: Philochem AG, Libernstrasse 3, CH-8112 Otelfingen, Switzerland.
authors.forename: Danilo
authors.initials: D
authors.lastname: Ritz
authors.affiliation: Philochem AG, Libernstrasse 3, CH-8112 Otelfingen, Switzerland.
authors.forename: Laura
authors.initials: L
authors.lastname: Gualandi
authors.affiliation: Philochem AG, Libernstrasse 3, CH-8112 Otelfingen, Switzerland.
authors.forename: Sarah
authors.initials: S
authors.lastname: Wulhfard
authors.affiliation: Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zürich), Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland. Electronic address: neri@pharma.ethz.ch.
authors.forename: Dario
authors.initials: D
authors.lastname: Neri
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000276:immunology; D002460:Cell Line; D045744:Cell Line, Tumor; D015870:Gene Expression / Q000235:genetics* / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D009369:Neoplasms / Q000235:genetics* / Q000276:immunology*; D019700:Thrombospondin 1 / Q000276:immunology*; D019699:Thrombospondins / Q000276:immunology*; D000099262:Thrombospondin 2
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D019700:Thrombospondin 1; D019699:Thrombospondins; D000099262:Thrombospondin 2
keywords: Cancer; Expression; Immunohistochemistry; Monoclonal antibody; Thrombospondin