title: Tumor vasculature: the Achilles' heel of cancer?
abstract: BACKGROUND
  Tumor-associated angiogenesis is one of the essential hallmarks underlying cancer development and metastasis. Anti-angiogenic agents accordingly aim to restrain cancer progression by blocking the formation of new vessels, improving the delivery of chemotherapeutic agents to the tumor site and reducing the shedding of metastatic cells into the circulation. This review article addresses some key issues in the use of angiogenesis inhibitors in cancer.
  
  
  METHODS
  The authors review the complex interactions between cell signaling pathways involved in tumor angiogenesis, and focus in particular on the molecular mechanisms that may induce resistance to angiogenesis inhibitors. They will also discuss some novel therapeutic strategies evolving within anti-angiogenic therapy such as the targeting of VEGFR-3, endothelial integrins and hepatocyte growth factor-MET signaling.
  
  
  CONCLUSIONS
  Although anti-angiogenic therapy is targeted at the non-malignant part of the tumor, the intricate network of growth promoting signaling pathways and in particular the redundancy when single pathways are targeted in endothelial cells represents a major therapeutic obstacle. A key challenge will be to develop more efficient inhibitors, combined with an individualized approach based on each tumor's own endothelial signaling profile. Furthermore, reliable biomarkers which pinpoint those patients that will benefit from anti-angiogenic therapy need to be identified.
authors.affiliation: University of Bergen, Department of Biomedicine, Jonas Lies vei 91, 5009 Bergen, Norway.
authors.forename: Tor-Christian Aase
authors.initials: TC
authors.lastname: Johannessen
authors.forename: Marek
authors.initials: M
authors.lastname: Wagner
authors.forename: Oddbjorn
authors.initials: O
authors.lastname: Straume
authors.forename: Rolf
authors.initials: R
authors.lastname: Bjerkvig
authors.forename: Hans Petter
authors.initials: HP
authors.lastname: Eikesdal
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D015398:Signal Transduction
chemical_list: D020533:Angiogenesis Inhibitors; D014408:Biomarkers, Tumor