title: Phenotypic knockout of VEGF-R2 and Tie-2 with an intradiabody reduces tumor growth and angiogenesis in vivo.
abstract: The endothelial cell receptor-tyrosine kinases, VEGF receptor 2 (VEGF-R2) and Tie-2, and their ligands, vascular endothelial growth factor (VEGF) and angiopoietins 1 and 2, respectively, play key roles in tumor angiogenesis. Several studies suggest that the VEGF receptor pathway and the Tie-2 pathway are independent and essential mediators of angiogenesis, leading to the hypothesis that simultaneous interference with both pathways should result in additive effects on tumor growth. In this study, a human melanoma xenograft model (M21) was used to analyze the effects of simultaneous intradiabody depletion of vascular endothelial growth receptor-R2 and Tie-2 on tumor angiogenesis and tumor xenograft growth. The intradiabodies were expressed from recombinant adenovirus delivered through subtumoral injection. Blockade of both VEGF-R2 and Tie-2 pathways simultaneously or the VEGF receptor pathway alone resulted in a significant inhibition of tumor growth and tumor angiogenesis (92.2% and 74.4%, respectively). In addition, immunohistochemical staining of intradiabody-treated tumors demonstrated a decreased number of tumor-associated blood vessels versus control treatment. Previous studies with intrabodies had demonstrated that the Tie-2 receptor pathway was essential for tumor growth. The simultaneous blockade of the VEGF and Tie-2 pathways resulted in effective inhibition of tumor growth and demonstrated the potential of simultaneous targeting of multiple pathways as a therapeutic strategy.
authors.affiliation: Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Nina
authors.initials: N
authors.lastname: Jendreyko
authors.forename: Mikhail
authors.initials: M
authors.lastname: Popkov
authors.forename: Christoph
authors.initials: C
authors.lastname: Rader
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Barbas
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D008545:Melanoma / Q000098:blood supply* / Q000276:immunology / Q000473:pathology* / Q000628:therapy; D051379:Mice; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic; D010641:Phenotype; D011817:Rabbits; D042787:Receptor, TIE-2 / Q000172:deficiency* / Q000276:immunology / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor / Q000172:deficiency* / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D007140:Immunoglobulin Fab Fragments; D042787:Receptor, TIE-2; D040262:Receptors, Vascular Endothelial Growth Factor