Pitfalls in the measurement of circulating vascular endothelial growth factor.
BACKGROUND
Vascular endothelial growth factor (VEGF) is a protein with antiapoptotic, mitogenic, and permeability-increasing activities specific for vascular endothelium. VEGF mRNA, which has five isoforms, is produced by nonmalignant cells in response to hypoxia and inflammation and by tumor cells in constitutively high concentrations. Because VEGF plays a crucial role in physiological and pathophysiological angiogenesis, measurements of circulating VEGF are of diagnostic and prognostic value, e.g., in cardiovascular failures, inflammatory diseases, and malignancies. However, there are major quantitative differences in the published results. This review attempts to identify reasons for these disparities.


METHODS
The literature was reviewed through a Medline search covering 1995 to 2000. A selection of exemplary references had to be made for this perspective overview.


BACKGROUND
Data are included from studies on healthy humans, gynecological patients, and persons suffering from inflammatory or malignant diseases. The results indicate that competitive immunoassays detect the total amount of circulating VEGF, which enables observations regarding the increase in VEGF in pregnancy and preeclampsia to be made. In these cases, capture immunoassays utilizing neutralizing antibodies are insufficient because of an accompanying increase in VEGF-binding soluble receptors (sFlt-1). Measurements of circulating free VEGF are useful for study of malignant diseases, which are associated with both genetically and hypoxia-induced overproduction of VEGF. The VEGF isoform specificity of the antibodies is also critical because both VEGF(121) and VEGF(165) are secreted. It is important to consider that platelets and leukocytes release VEGF during blood clotting.


CONCLUSIONS
Future efforts should concentrate on the balance between free VEGF, total VEGF, and sFlt-1. Plasma, rather than serum, should be used for analysis.
Institut für Physiologie, Medizinische Universität zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany. jelkmann@physio.mu-luebeck.de
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D016228:Endothelial Growth Factors / Q000097:blood* / Q000235:genetics; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism; D008222:Lymphokines / Q000097:blood* / Q000235:genetics; D009369:Neoplasms / Q000098:blood supply / Q000378:metabolism; D009389:Neovascularization, Pathologic; D011247:Pregnancy; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors