title: Vascular endothelial growth factor-mediated decrease in plasma soluble vascular endothelial growth factor receptor-2 levels as a surrogate biomarker for tumor growth.
abstract: Vascular endothelial growth factor (VEGF) is a potent proangiogenic protein that activates VEGF receptor (VEGFR) tyrosine kinases expressed by vascular endothelial cells. We previously showed that one of these receptors, VEGFR-2, has a truncated soluble form (sVEGFR-2) that can be detected in mouse and human plasma. Because activation of VEGFR-2 plays an important role in tumor angiogenesis, clinical interest in monitoring plasma sVEGFR-2 levels in cancer patients has focused on its potential exploitation as a surrogate biomarker for disease progression as well as assessing efficacy/activity of antiangiogenic drugs, particularly those that target VEGF or VEGFR-2. However, no preclinical studies have been done to study sVEGFR-2 during tumor growth or the mechanisms involved in its modulation. Using spontaneously growing tumors and both localized and metastatic human tumor xenografts, we evaluated the relationship between sVEGFR-2 and tumor burden as well as underlying factors governing protein level modulation in vivo. Our results show an inverse relationship between the levels of sVEGFR-2 and tumor size. Furthermore, using various methods of VEGF overexpression in vivo, including cell transfection and adenoviral delivery, we found plasma sVEGFR-2 decreases to be mediated largely by tumor-derived VEGF. Finally, in vitro studies indicate VEGF-mediated sVEGFR-2 modulation is the result of ligand-induced down-regulation of the VEGFR-2 from the cell surface. Taken together, these findings may be pertinent to further clinical exploitation of plasma sVEGFR-2 levels as a surrogate biomarker of VEGF-dependent tumor growth as well as an activity indicator of antiangiogenic drugs that target the VEGFR system.
authors.affiliation: Sunnybrook Health Sciences Centre, Molecular and Cellular Biology Research, University of Toronto, Toronto, Ontario, Canada.
authors.forename: John M L
authors.initials: JM
authors.lastname: Ebos
authors.forename: Christina R
authors.initials: CR
authors.lastname: Lee
authors.forename: Elena
authors.initials: E
authors.lastname: Bogdanovic
authors.forename: Jennifer
authors.initials: J
authors.lastname: Alami
authors.forename: Paul
authors.initials: P
authors.lastname: Van Slyke
authors.forename: Giulio
authors.initials: G
authors.lastname: Francia
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Mutsaers
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Dumont
authors.forename: Robert S
authors.initials: RS
authors.lastname: Kerbel
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000256:Adenoviridae; D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood*; D049109:Cell Proliferation; D005260:Female; D019073:HT29 Cells; D006801:Humans; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009368:Neoplasm Transplantation; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D012995:Solubility; D014161:Transduction, Genetic; D014183:Transplantation, Heterologous; D047368:Tumor Burden / Q000235:genetics; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000502:physiology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000097:blood* / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2