VEGFR-2 expression in human melanoma: Revised assessment

Kerrington R. Molhoek, Gulsun Erdag, Jk Rasamny, Cheryl Murphy, Donna Deacon, James W. Patterson, Craig L. Slingluff, David L. Brautigan

Research output: Contribution to journalArticlepeer-review

Abstract

Vascular endothelial growth factor (VEGF) is an angiogenic factor that also functions as an autocrine growth factor for VEGF receptor (VEGFR)-2 + melanomas. In multiple studies, VEGFR-2 was detected by immunostaining in 78-89% of human melanoma cells, suggesting that most patients with melanoma would benefit from anti-VEGF therapy. Here, we evaluated 167 human melanoma specimens in a tissue microarray to verify the presence of VEGFR-2, but found disparities in staining with commercial antibodies A-3 and 55B11. Antibody A-3 stained melanoma cells in 79% of specimens, consistent with published results; however, we noted extensive nonspecific staining of other cells such as smooth muscle and histiocytes. In contrast, antibody 55B11 stained melanoma cells in only 7% (95% confidence interval: 3.3-11.5) of specimens. As an internal positive control for VEGFR-2 detection, vascular endothelial cells were stained with antibody 55B11 in all specimens. We compared VEGFR-2 + and VEGFR-2 - melanoma cell lines by immunoblotting and immunohistochemistry after small interfering RNA (siRNA) knockdown and transient overexpression of VEGFR-2 to validate antibody specificity. Immunoblotting revealed that A-3 primarily cross-reacted with several proteins in both cell lines and these were unaffected by siRNA knockdown of VEGFR-2. In contrast, 55B11 staining of VEGFR-2 + cells was mostly eliminated by siRNA knockdown of VEGFR-2 and increased in VEGFR-2 - melanoma cell lines following transfection to express ectopic VEGFR-2. Our results show that relatively few melanoma cells (<10%) express detectable levels of VEGFR-2, and therefore, the majority of patients with melanoma are unlikely to benefit from antiproliferative effects of anti-VEGF therapy.

Original languageEnglish (US)
Pages (from-to)2807-2815
Number of pages9
JournalInternational Journal of Cancer
Volume129
Issue number12
DOIs
StatePublished - Dec 15 2011

Keywords

  • autocrine
  • bevacizumab
  • immunohistochemistry
  • siRNA
  • tissue microarray

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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