title: The antitumor and antiangiogenic activity of vascular endothelial growth factor receptor inhibition is potentiated by ErbB1 blockade.
abstract: OBJECTIVE
  Receptor tyrosine kinases of the ErbB family play important roles in the control of tumor growth. Vascular endothelial growth factor (VEGF) stimulates endothelial cell proliferation, enhances vascular permeability, and plays an important role in tumor vascularization. We evaluated the effects of selective VEGF receptor (VEGFR; PTK787/ZK222584) and ErbB (PKI166 and ZD1839) inhibitors on tumor growth and angiogenesis and asked whether additional therapeutic benefit was conferred by combination treatment.
  
  
  METHODS
  The antitumor activity of each inhibitor alone or in combination was assessed in human cancer models in immunocompromised mice. ErbB receptor expression and activation of downstream signaling pathway was evaluated in both tumor and endothelial cells.
  
  
  RESULTS
  Both ErbB inhibitors significantly enhanced the antitumor activity of PTK787/ZK222584. In vitro, ErbB1 inhibition blocked VEGF release by tumor cells and proliferation of both tumor and endothelial cells. In an in vitro angiogenesis assay, epidermal growth factor (EGF) stimulated the release of VEGF by smooth muscle cells resulting in increased angiogenesis, a response blocked by administration of PTK787/ZK222584. Under basal condition, both ZD1839 and PTK787/ZK222584 blocked sprouting, likely via inhibition of an autocrine ErbB1 loop and VEGFR signaling, respectively, in endothelial cells. In conditions of limiting VEGF, EGF plays an important role in endothelial cell proliferation, survival, and sprouting.
  
  
  CONCLUSIONS
  We have shown that activation of ErbB1 triggers a plethora of effects, including direct effects on tumor and endothelial cells and indirect effects mediated via induction of VEGF release. Simultaneous blockade of ErbB1 and VEGFR pathways results in a cooperative antitumor effect, indicating that this combination may represent a valid therapeutic strategy.
authors.affiliation: Novartis Institute for Biomedical Research, Oncology Research, Basel, Switzerland. Patrizia.Sini@novartis.com
authors.forename: Patrizia
authors.initials: P
authors.lastname: Sini
authors.forename: Lorenza
authors.initials: L
authors.lastname: Wyder
authors.forename: Christian
authors.initials: C
authors.lastname: Schnell
authors.forename: Terence
authors.initials: T
authors.lastname: O'Reilly
authors.forename: Amanda
authors.initials: A
authors.lastname: Littlewood
authors.forename: Ralph
authors.initials: R
authors.lastname: Brandt
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Hynes
authors.forename: Jeanette
authors.initials: J
authors.lastname: Wood
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D004357:Drug Synergism; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D000077156:Gefitinib; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D010793:Phthalazines / Q000494:pharmacology*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology*; D014183:Transplantation, Heterologous; D042461:Vascular Endothelial Growth Factor A / Q000097:blood / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D010793:Phthalazines; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D011799:Quinazolines; D042461:Vascular Endothelial Growth Factor A; C404768:vatalanib; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D000077156:Gefitinib