title: Dual targeting of the type 1 insulin-like growth factor receptor and its ligands as an effective antiangiogenic strategy.
abstract: BACKGROUND
  In pediatric tumor xenograft models, tumor-derived insulin growth factor (IGF-2) results in intrinsic resistance to IGF-IR-targeted antibodies, maintaining continued tumor angiogenesis. We evaluated the antiangiogenic activity of a ligand-binding antibody (MEDI-573) alone or in combination with IGF-I receptor binding antibodies (MAB391, CP01-B02).
  
  
  METHODS
  IGF-stimulated signaling was monitored by increased Akt phosphorylation in sarcoma and human umbilical cord vascular endothelial cells (HUVEC). Angiogenesis was determined in vitro using capillary tube formation in HUVECs and in vivo using a VEGF-stimulated Matrigel assay. Tumor growth delay was examined in 4 sarcoma xenograft models.
  
  
  RESULTS
  The IGF ligand-binding antibody MEDI-573 suppressed Akt phosphorylation induced by exogenous IGF-I and IGF-2 in sarcoma cells. Receptor-binding antibodies suppressed IGF-I stimulation of Akt phosphorylation, but IGF-2 circumvented this effect and maintained HUVEC tube formation. MEDI-573 inhibited HUVEC proliferation and tube formation in vitro, but did not inhibit angiogenesis in vivo, probably because MEDI-573 binds murine IGF-I with low affinity. However, in vitro antiangiogenic activity of MEDI-573 was also circumvented by human recombinant IGF-I. The combination of receptor- and ligand-binding antibodies completely suppressed VEGF-stimulated proliferation of HUVECs in the presence of IGF-I and IGF-2, prevented ligand-induced phosphorylation of IGF-IR/IR receptors, and suppressed VEGF/IGF-2-driven angiogenesis in vivo. The combination of CP1-BO2 plus MEDI-573 was significantly superior to therapy with either antibody alone against IGF-I and IGF-2 secreting pediatric sarcoma xenograft models.
  
  
  CONCLUSIONS
  These results suggest that combination of antibodies targeting IGF receptor and ligands may be an effective therapeutic strategy to block angiogenesis for IGF-driven tumors.
authors.affiliation: Center for Childhood Cancer, Nationwide Children's Hospital, Columbus, Ohio 43205, USA.
authors.forename: Hemant K
authors.initials: HK
authors.lastname: Bid
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: London
authors.forename: Jin
authors.initials: J
authors.lastname: Gao
authors.forename: Haihong
authors.initials: H
authors.lastname: Zhong
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hollingsworth
authors.forename: Soledad
authors.initials: S
authors.lastname: Fernandez
authors.forename: Xiaokui
authors.initials: X
authors.lastname: Mo
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Houghton
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D008024:Ligands; D051379:Mice; D009389:Neovascularization, Pathologic / Q000188:drug therapy; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012509:Sarcoma / Q000188:drug therapy / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D008024:Ligands; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1
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