The B-Raf status of tumor cells may be a significant determinant of both antitumor and anti-angiogenic effects of pazopanib in xenograft tumor models

PLoS One. 2011;6(10):e25625. doi: 10.1371/journal.pone.0025625. Epub 2011 Oct 5.

Abstract

Pazopanib is an FDA approved Vascular Endothelial Growth Factor Receptor inhibitor. We previously reported that it also inhibits tumor cell B-Raf activity in an experimental brain metastatic setting. Here, we determine the effects of different B-Raf genotypes on pazopanib efficacy, in terms of primary tumor growth and anti-angiogenesis. A panel of seven human breast cancer and melanoma cell lines harboring different mutations in the Ras-Raf pathway was implanted orthotopically in mice, and tumor growth, ERK1/2, MEK1/2 and AKT activation, and blood vessel density and permeability were analyzed. Pazopanib was significantly inhibitory to xenografts expressing either exon 11 mutations of B-Raf, or HER2 activated wild type B-Raf; no significant inhibition of a xenograft expressing the common V600E B-Raf mutation was observed. Decreased pMEK staining in the responsive tumors confirmed that B-Raf was targeted by pazopanib. Interestingly, pazopanib inhibition of tumor cell B-Raf also correlated with its anti-angiogenic activity, as quantified by vessel density and area. In conclusion, using pazopanib, tumor B-Raf status was identified as a significant determinant of both tumor growth and angiogenesis.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Angiogenesis Inhibitors / pharmacology
  • Angiogenesis Inhibitors / therapeutic use
  • Animals
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use
  • Breast Neoplasms / blood supply
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / pathology*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Female
  • Humans
  • Indazoles
  • MAP Kinase Signaling System / drug effects
  • Melanoma / blood supply
  • Melanoma / enzymology
  • Melanoma / pathology*
  • Mice
  • Neovascularization, Pathologic / drug therapy*
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors
  • Proto-Oncogene Proteins B-raf / metabolism*
  • Pyrimidines / pharmacology*
  • Pyrimidines / therapeutic use
  • Sulfonamides / pharmacology*
  • Sulfonamides / therapeutic use
  • Xenograft Model Antitumor Assays*

Substances

  • Angiogenesis Inhibitors
  • Antineoplastic Agents
  • Indazoles
  • Pyrimidines
  • Sulfonamides
  • pazopanib
  • Proto-Oncogene Proteins B-raf