Immunodetection and molecular forms of plasma vascular endothelial growth factor-C

Vascular endothelial growth factor (VEGF)-C is a member of the VEGF family. VEGF-C is involved in developmental lymphangiogenesis and may be important in pathological lymphangiogenesis, lymphatic invasion and metastasis in carcinoma. We describe the development of an indirect enzyme-linked immunosorbent (ELISA) assay for the quantification of VEGF-C in plasma. Capture of VEGF-C was achieved using goat anti-human VEGF-C antibody, followed by detection with rabbit anti-human VEGF-C antibody. The sensitivity of the assay was amplified using the biotin-avidin and enhanced chemiluminescence (ECL) systems. The assay was highly sensitive and reproducible with a detection range of 0.4-100 U/ml and the intra- and inter-assay variations were less than 8%. Substitutional tests demonstrated that the assay was specific for VEGF-C with no cross-reaction with VEGF-A or VEGF-D. Practical application of the assay was evaluated in 41 colorectal cancer patients and 31 controls. Median plasma levels of VEGF-C were 35.0 U/ml (range: 17.4-75.9 U/ml) in colorectal cancer patients in contrast to 11.5 U/ml (range: 5.4-21.5 U/ml) in controls (p<0.001). Moreover, VEGF-C levels tended to be elevated in patients with advanced disease compared to early disease, but this was not statistically significant owing to a relatively small number of patients in each group. Immunoprecipitation and immunoblotting confirmed detection of VEGF-C in plasma and revealed that two forms of VEGF-C were present in the plasma corresponding to ∼40 and ∼80 kDa. The measurement of plasma VEGF-C offers opportunities to explore clinical applications in the management of malignancy, in particular in the prediction of lymphatic spread and in other lymphangiogenesis-related diseases.