title: Limitations of the dorsal skinfold window chamber model in evaluating anti-angiogenic therapy during early phase of angiogenesis.
abstract: BACKGROUND
  Angiogenesis is an essential process during tumor development and growth. The murine dorsal skinfold window chamber model has been used for the study of both tumor microvasculature and other vascular diseases, including the study of anti-angiogenic agents in cancer therapy. Hyperspectral imaging of oxygen status of the microvasculature has not been widely used to evaluate response to inhibition of angiogenesis in early tumor cell induced vascular development. This study demonstrates the use of two different classes of anti-angiogenic agents, one targeting the Vascular Endothelial Growth Factor (VEGF) pathway involved with vessel sprouting and the other targeting the Angiopoietin/Tie2 pathway involved in vascular destabilization. Studies evaluated the tumor microvascular response to anti-angiogenic inhibitors in the highly angiogenic renal cell carcinoma induced angiogenesis model.
  
  
  METHODS
  Human renal cell carcinoma, Caki-2 cells, were implanted in the murine skinfold window chamber. Mice were treated with either VEGF pathway targeted small molecule inhibitor Sunitinib (100 mg/kg) or with an anti-Ang-2 monoclonal antibody (10 mg/kg) beginning the day of window chamber surgery and tumor cell implantation. Hyperspectral imaging of hemoglobin saturation was used to evaluate both the development and oxygenation of the tumor microvasculature. Tumor volume over time was also assessed over an 11-day period post surgery.
  
  
  RESULTS
  The window chamber model was useful to demonstrate the inhibition of angiogenesis using the VEGF pathway targeted agent Sunitinib. Results show impairment of tumor microvascular development, reduced oxygenation of tumor-associated vasculature and impairment of tumor volume growth compared to control. On the other hand, this model failed to demonstrate the anti-angiogenic effect of the Ang-2 targeted agent. Follow up experiments suggest that the initial surgery of the window chamber model may interfere with such an agent thus skewing the actual effects on angiogenesis.
  
  
  CONCLUSIONS
  Results show that this model has great potential to evaluate anti-VEGF, or comparable, targeted agents; however the mere protocol of the window chamber model interferes with proper evaluation of Ang-2 targeted agents. The limitations of this in vivo model in evaluating the response of tumor vasculature to anti-angiogenic agents are discussed.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Cancer and Genetics Research Complex, 2033 Mowry Rd., Gainesville FL 32610, USA.
authors.forename: Nikolett M
authors.initials: NM
authors.lastname: Biel
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Biomedical Sciences Building, Gainesville FL 32610, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Lee
authors.affiliation: Cancer Diagnosis Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, Rockville MD 20852, USA.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Sorg
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Cancer and Genetics Research Complex, 2033 Mowry Rd., Gainesville FL 32610, USA ; Department of Radiation Oncology, University of Florida College of Medicine, 2000 SW Archer Road, Gainesville FL 32610, USA.
authors.forename: Dietmar W
authors.initials: DW
authors.lastname: Siemann
keywords: Angiogenesis; Angiopoietin-2; Anti-angiogenic therapy; Dorsal skinfold window chamber model; Vascular endothelial growth factor
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