Biological variations in plasma VEGF and VEGFR-1 may compromise their biomarker value in colorectal cancer

Abstract

Introduction. Vascular Endothelial Growth Factor (VEGF) plays a prominent role in tumor angiogenesis and plasma VEGF concentration may carry prognostic information in colorectal cancer. The VEGF receptor 1 (VEGFR-1) is a regulatory receptor which is shredded into plasma of patients with colorectal cancer. For both molecules, large biological variation and lack of standardization of assay procedures are major challenges. Methods. We investigated pre-analytical, analytical, as well as short term and long term biological variation of plasma VEGF and VEGFR-1 in volunteers. In addition, we evaluated plasma VEGF and VEGFR-1 as markers of colorectal disease in a case-control study on four groups of 77 individuals undergoing bowel endoscopy. Groups were categorized as ‘no findings’, ‘non-malignant findings’, ‘adenoma’, or ‘colorectal cancer’. Results. In the studies on variation, temperature and delay before centrifugation significantly influenced plasma VEGF and, to a minor extent, plasma VEGFR-1 concentrations. In addition, we found large biological variations with CV up to 69.2% for VEGF and CV up to 35.9% for VEGFR-1. For both molecules the intra-subject variation exceeded the inter-subject variation. In the case control study neither plasma VEGF nor VEGFR-1 was able to differentiate between the four groups of individuals although plasma VEGFR-1 was significantly lower in patients with ‘no findings’. Conclusion. There was no difference in plasma VEGF or VEGFR-1 between patients with no findings, benign disease, pre-malignant findings, and malignant findings after endoscopy. The poor discrimination between patients may be explained by the large inter- and intra-subject variations found for both molecules in volunteers.

Key Words::

• Biological variation
• blood plasma
• diagnostic marker
• EDTA plasma
• biological variation
• vascular endothelial growth factor A
• vascular endothelial growth factor receptor-1

Acknowledgements

The authors thank Ms. Birgitte Sander Nielsen and Vibeke Jensen for skilful work during analyses of the samples. Similarly, The Danish-Australian Colorectal Cancer Study Group is thanked for collection of samples and recording of data in the Endoscopy study.

Financial disclosure: The authors have no financial or other conflict of interest that may bias the work. The study received financial support from The Kornerup Fund, The Aase and Ejnar Danielsen Fund, The Aage and Johanne Louis-Hansen Fund, The Walter and O. Kristiane Christensen Fund, The Hans and Nora Buchard Fund, The Bent and Inge Bøgh Fund, The Kurt and Grethe Bønnelycke Fund, The A. Espersen Fund, The Max Fodgaard Fund, The Johannes Fog Fund, The Sofus and Olga Friis Fund, The Eva and Henry Frænkel Fund, The Edith and Søren Hansen Fund, The Niels and Johanne Hansen Fund, The Hartmann Bros. Fund, The Sophus and Astrid Jacobsen Fund, The Justesen Family Fund, The Mimi and Victor Larsen Fund, The MICA Fund, The Arvid Nilsson Fund, The Frode Nyegaard Fund, The Sigvald and Edith Rasmussen Fund, The Else and Ole Trock-Jansen Fund, The Velux Foundation, The Einar Willumsen Fund, and The Danish Cancer Society (HJN is Danish Cancer Society Professor of Surgical Oncology).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.