Circulating levels of VEGF-A, VEGF-D and soluble VEGF-A receptor (sFIt-1) in human breast cancer.

As circulating levels of vascular endothelial growth factor (VEGF-A) are raised in malignancy, the aim of this study was to investigate whether similar changes occur in two related factors, VEGF-D and the soluble VEGF-A receptor FIt-1 (sFIt-1). Circulating levels of VEGF-A, VEGF-D and sFIt-1 were determined by ELISA in 51 patients with primary breast cancer and matched healthy controls. Results were correlated with clinicopathological data. Whilst there was a difference in VEGF-A levels between patient and control groups (p = 0.03), no such difference was observed for sFIt-1 or VEGF-D levels and there was no association between individual factors and the clinicopathological variables examined. However, there was a positive correlation between VEGF-A and sFIt-1 levels in both patient and control groups (p < 0.0001). In addition, the ratio of sFIt-1 to VEGF-A was significantly different between patients and controls (p < 0.0001) and was also associated with tumour size (p = 0.01) within the patient group. During tumour progression there is a change in the relative amounts of sFIt-1 and VEGF-A in the circulation. Measuring the sFIt-1:VEGF-A ratio may have more significance than VEGF-A alone and further studies are needed to determine whether the ratio is of use as a prognostic marker or as a means of monitoring response to anti-angiogenic therapy in cancer.

Localisation of members of the vascular endothelial growth factor (VEGF) family and their receptors in human atherosclerotic arteries.

BACKGROUND: Vascular endothelial growth factor (VEGF) mediates endothelial cell mitogenesis and enhances vascular permeability. The existence of single or multiple VEGF isoforms and receptors suggests that these proteins may have overlapping but distinct functions, which may be reflected in their cell expression and distribution. METHODS: The localisation of VEGFs A-C and their receptors (VEGFRs 1-3, respectively) in 30 fresh human atherosclerotic arteries, 15 normal uterine arteries, and 15 saphenous veins using immunohistochemistry and western blotting. RESULTS: Saphenous veins showed no staining for VEGF-B or VEGFR-2. Smooth muscle cells (SMCs) showed the strongest staining for VEGF-A, VEGF-B, VEGFR-1, and VEGFR-2 in all specimens. Conversely, VEGFR-3 and VEGF-C were predominantly localised to the endothelial vasa vasorum in normal arteries, whereas medial SMCs showed the strongest staining in atherosclerotic arteries. Western blotting showed variations in VEGF protein localisation, with lower amounts of VEGF-B and VEGF-C in saphenous veins, compared with arterial tissue. Amounts of VEGF-C were lower than those of VEGF-A and VEGF-B in all specimens. CONCLUSION: This study provides direct evidence of the presence of VEGF proteins and receptors in human physiology and pathology, with variations in both the amounts of VEGF proteins expressed and their cellular distribution in normal arteries compared with atherosclerotic arteries. The presence of VEGFs A-C and their receptors in normal arterial tissue implies that VEGF functions may extend beyond endothelial cell proliferation. Reduced VEGFR-2 staining in atherosclerotic arteries may have implications for the atherosclerosis process and the development of vascular disease and its complications.

Angiogenesis, thrombogenesis, endothelial dysfunction and angiographic severity of coronary artery disease.

BACKGROUND: Thrombogenesis, angiogenesis, and endothelial damage/dysfunction are components in the pathogenesis of atherosclerosis. OBJECTIVE: To investigate the relation of these variables to atherosclerotic disease severity and the possible interrelations between the three. METHODS: 111 patients attending for coronary angiography were studied (85 male, 26 female; mean (SD) age, 61.6 (10.0) years). Plasma concentrations of von Willebrand factor (vWf, a marker of endothelial damage/dysfunction), vascular endothelial growth factor (VEGF, associated with angiogenesis), soluble VEGF receptor Flt-1 (sFlt-1), and tissue factor (TF, a key component of coagulation) were measured by an enzyme linked immunosorbent assay. Following angiography, disease severity was assessed by the number of coronary vessels diseased (> 50% stenosis) and by a coronary atheroma score. RESULTS: All indices were raised in the patients compared with 34 healthy controls except sFlt-1, which was lower in the patients. No significant correlations were found between the coronary atheroma score and values of vWf (Spearman correlations: r = 0.21, p = 0.83), VEGF (r = 0.11, p = 0.27), or TF (r = -0.04, p = 0.68). However, there was an inverse correlation between plasma sFlt-1 and coronary atheroma score (r = -0.19, p = 0.049). The number of vessels diseased had no relation to any marker. Correlations were found between TF and VEGF (r = 0.25, p = 0.008) and between TF and sFlt-1 (r = 0.42, p < 0.001) in the patients. CONCLUSIONS: Despite evidence of abnormal angiogenesis (VEGF and sFlt-1), thrombogenesis (TF), and endothelial damage/dysfunction (vWf) in the patients with coronary artery disease, there was no correlation between VEGF, sFlt-1, vWf, or TF and angiographically defined disease severity.

Basic fibrobrast growth factor induces the secretion of vascular endothelial growth factor by human aortic smooth muscle cells but not by endothelial cells.

BACKGROUND: Endothelial cell dysfunction and smooth muscle cell (SMC) proliferation are major events in atherogenesis. Both cells are a source of growth factors that mediate cellular proliferation and chemotaxis. Inappropriate production of, and/or response to, these growth factors (such as vascular endothelial growth factor, VEGF, and basic fibroblast growth factor (bFGF)) may contribute to atherogenesis and therefore to disease progression. METHODS: Production of VEGF and its soluble receptor (sFlt-1) by human SMCs and human umbilical endothelial cells (HUVECs) after stimulation with bFGF were examined by ELISA of cell culture media and by Western blotting. RESULTS: Smooth muscle cells produced significantly more VEGF than HUVECs (P<0.05) after 24 h of culture with bFGF levels > or =0.001 microg mL(-1). bFGF induced dose-dependent production of VEGF by SMCs, where maximum production was present in 1 microg mL(-1) of bFGF. Conversely, the SMCs produced less sFlt-1 than HUVECs (P<0.05). However, bFGF induced dose-dependent phosphorylation of Flt1 and another VEGF receptor, KDR, in HUVECs but not SMCs. There was no VEGF or sFLT-1 after 6 h of culture in any dose of bFGF in either type of cell. CONCLUSIONS: Differences in the production of VEGF and sFlt-1 by SMCs and HUVECs are consistent with the role of these cells in angiogenesis. Induction of VEGF production and expression by bFGF in these cells indicates that this growth factor may participate in angiogenesis indirectly by the induction of VEGF. The production of sFlt-1 by both cell types is in agreement with the notion that sFlt-1 may be involved in the regulation of VEGF activity. Additionally, the ability of bFGF to induce dose-dependent phosphorylation of KDR in HUVECs highlights the important role of bFGF in VEGF-mediated angiogenic processes.

Angiogenesis in myocardial infarction. An acute or chronic process?

BACKGROUND: In the acute phase of myocardial infarction (acute MI) marked endothelial damage occurs within the first 24h following thrombolysis with streptokinase. We investigated whether this is associated with a change in levels of vascular endothelial growth factor (VEGF, possibly marking angiogenesis) in the first 24h post thrombolysis compared to chronic MI patients (defined as MI>3 months previously). METHODS: We recruited 15 patients (nine male, mean age 59+/-SD 10 years) with first-presentation acute MI, who were given 1.5 million U streptokinase over 1h and aspirin 300mg orally as standard treatment. Plasma samples were taken prior to the start of thrombolysis, followed every 15 min for 1h, at 3h and finally at 24h post-thrombolysis. Baseline levels of measured indices in the acute MI patients were compared to two control groups: (i) 26 chronic MI patients (18 male, mean age 59.9+/-7.0 years); and (ii) 26 apparently healthy controls (17 male, mean age 59.6+/-14.1 years). Plasma VEGF and the soluble form of its receptor Flt-1 (sFlt-1) were measured by ELISA. RESULTS: Plasma levels of VEGF were significantly higher in patients with a history of chronic MI compared to patients with acute MI (P=0.007) and healthy controls (P=0.002) with similar levels between acute MI patients and healthy controls (P=0.755). Levels of sFlt-1 in the acute (P=0.013) and chronic (P<0.001) MI groups were lower compared to healthy controls. In the first 24h post-thrombolysis in the acute MI group, levels of sFlt-1 changed significantly (P=0.039), but there was no change in levels of VEGF (P=0.207). CONCLUSION: In the first 24h of acute MI, significant changes in levels of VEGF receptor sFlt-1, but not VEGF, are seen. Plasma VEGF and sFlt-1 levels are markedly changed in chronic MI patients, suggesting that the activation of angiogenesis in MI patients may be a delayed response.

Plasma levels of vascular endothelial growth factor (VEGF) and its receptor, Flt-1, in haematological cancers: a comparison with breast cancer.

Raised plasma VEGF is found in some cancers but levels of its receptor soluble Flt-1 (sFlt-1) are unreported. Hypothesising increased levels to be present in haematological cancers, we measured both by ELISA in 22 patients with haematological cancer, 22 with breast cancer, and in age- and sex-matched controls. VEGF was raised in both patients groups compared to controls (P < 0.01) but was higher in haematological cancer compared to breast cancer (P = 0.0238). There was no difference in levels of sFlt-1. Our data point to changes in levels of plasma VEGF, but not sFlt-1, in haematological cancer that may have pathophysiological consequences.

Plasma vascular endothelial growth factor and its receptor Flt-1 in patients with hyperlipidemia and atherosclerosis and the effects of fluvastatin or fenofibrate.

Increased vascular endothelial cell growth factor (VEGF) may be important in cardiovascular pathophysiology (perhaps relating to angiogenesis and collateral vessel development) and binds target endothelium via receptors such as Flt-1. We hypothesized that there would be increased levels of plasma VEGF and Flt-1 in patients with atherosclerosis and others with hyperlipidemia compared with controls, and a reduction in these factors with 3 months of lipid-lowering therapy. Twenty patients with uncomplicated hyperlipidemia but no atherosclerosis, 20 patients with hyperlipidemia plus clear atherosclerosis, and 40 matched controls were studied. Plasma VEGF was higher in patient groups than in healthy controls (p <0.01), but Flt-1 was not significantly altered. After lipid-lowering therapy, patients with uncomplicated hyperlipidemia had significantly reduced total cholesterol and VEGF (all p <0.05) but no significant change in Flt-1. Lack of a significant correlation between the von Willebrand factor and VEGF suggests the latter is unrelated to endothelial damage. Plasma VEGF that increases in patients with uncomplicated hyperlipidemia free of major underlying atherosclerosis and in patients with hyperlipidemia plus established atherosclerosis is reduced by successful lipid-lowering treatment. These findings may have implications for the pathophysiology and treatment of hyperlipidemia and atherosclerosis, and suggest an alternative mechanism (i.e., modulation of angiogenesis) by which lipid-lowering therapy may reduce cardiovascular events beyond lipid reduction alone.

Measurement of free and complexed soluble vascular endothelial growth factor receptor, Flt-1, in fluid samples: development and application of two new immunoassays.

Vascular endothelial growth factor (VEGF) mediates endothelial cell mitogenesis and enhances vascular permeability. VEGF interacts with the endothelium via two membrane-spanning receptors, fms-like tyrosine kinase (Flt)-1 and kinase domain receptor. A soluble form of Flt-1 (sFlt-1) was isolated from endothelial cell media; however, its biological significance is still unknown, with limited data on plasma sFlt-1 levels in disease states. We have developed two new ELISAs for detecting free and VEGF-complexed sFlt-1, which were tested in accordance with standard validation and assessment methodologies employed in commercial settings. The intra-and inter-assay coefficients of variation are <5% and 10% respectively, and results are highly reproducible. Applying these ELISAs in a clinical setting, we measured levels of VEGF, free and complexed sFlt-1 in citrated plasma from 40 patients with cardiovascular disease and 40 healthy controls. Median (interquartile range) plasma levels of VEGF in patients were significantly greater than controls [403 pg/ml (158--925 pg/ml) versus 113 pg/ml (33--231 pg/ml), P< or =0.05]. Free sFlt-1 was significantly lower in patients compared with controls [8 ng/ml (2--22 ng/ml) versus 21 ng/ml (10--73 ng/ml), P< or =0.05]. There was no significant difference in the levels of complexed sFlt-1 between the two groups. Plasma levels of VEGF-complexed sFlt-1 are minimal, despite the presence of excess free sFlt-1. Thus unbound plasma VEGF detected by ELISA may represent the majority of circulating VEGF, and justifies the measurement of plasma VEGF as an indicator of circulating VEGF levels. Furthermore, these results suggest that circulating sFlt-1 may serve as a selective inhibitor of VEGF activity, and that this regulatory mechanism may be altered by pathological conditions.

Plasma levels of vascular endothelial growth factor and its soluble receptor (SFlt-1) in essential hypertension.

In this study of 27 untreated patients with uncomplicated essential hypertension, we report on elevated plasma levels of vascular endothelial growth factor and its soluble receptor Flt-1 compared with healthy controls; these increased levels are reduced by the treatment of hypertension. This raises the possibility that abnormal angiogenesis may contribute to the pathogenesis of complications related to hypertension and merits exploration in larger studies.

Vascular endothelial growth factor and its receptor, Flt-1, in smokers and non-smokers.

Raised levels of plasma vascular endothelial growth factor (VEGF) are found in some cancers, diabetes, and certain other conditions, but levels of its receptor, soluble Flt-1 (sFlt-1), in these diseases have yet to be reported. We hypothesised that smoking would influence levels of these molecules. Consequently, we measured VEGF and sFlt-1 by enzyme-linked immunosorbent assay (ELISA) in plasma from 92 non-smokers and 35 smokers. No difference in VEGF was seen between the groups but, despite considerable overlap, sFlt-1 was significantly lower in smokers (P = 0.027). VEGF and sFlt-1 correlated strongly with each other (P < 0.001). Although VEGF may arise from a number of cell types, including endothelial cells, the primary source of sFlt-1 is thought to be the endothelium; however, neither VEGF nor sFlt-1 correlated with levels of the endothelial cell activation/damage marker soluble thrombomodulin. Our data point to changes in levels of the VEGF receptor, sFlt-1--but not VEGF itself--in smokers, which appears to be unrelated to endothelial cell function.

Plasma VEGF and soluble VEGF receptor FLT-1 in proliferative retinopathy: relationship to endothelial dysfunction and laser treatment.

PURPOSE: To study plasma levels of vascular endothelial growth factor (VEGF, an index of angiogenesis), its soluble receptor (sFlt-1) and von Willebrand factor (vWf, an index of endothelial damage or dysfunction) in patients with proliferative retinopathy and corresponding changes in plasma levels after pan-retinal photocoagulation (PRP). METHODS: Eighteen patients (10 men; age, 57+/-16 years, mean +/- SD) with proliferative retinopathy secondary to diabetes (n = 13) and ischemic retinal vein occlusion (n = 5) with no previous PRP therapy were studied. Blood samples were obtained before and at 4 months after the last PRP session. Baseline (prelaser) plasma levels of VEGF, sFlt-1, and vWf (all by ELISA) were compared with levels in 16 diabetic patients with background retinopathy ("hospital controls"), and 18 healthy, age- and sex-matched "healthy controls." RESULTS: Patients with proliferative retinopathy had significantly raised plasma VEGF when compared with both control groups (P = 0.001). Patients with proliferative retinopathy and hospital controls had significantly raised plasma vWf levels when compared with healthy controls (P = 0.012). There was no difference in sFlt-1 levels between patients and controls (P = 0.162). After PRP, there was a significant reduction in plasma VEGF levels at 4 months' follow-up (P < 0.001), but no significant changes in plasma sFlt-1 or vWf levels. Patients with complete resolution of neovascularization had a trend toward lower median VEGF levels (80 versus 150 pg/ml, P = 0.062), but vWf levels (P = 0.50) and sFlt-1 (P = 0.479) were not statistically different. Baseline VEGF and sFlt-1 levels were significantly correlated (Spearman r = 0.505, P = 0.032) but after PRP at 4 months' follow-up, this was no longer significant (r = -0.269, P = 0.28). CONCLUSIONS: In this pilot study, patients with proliferative retinopathy demonstrate elevated peripheral markers of angiogenesis and endothelial dysfunction, suggesting a role for these processes in the pathogenesis of this condition. A fall in levels of VEGF after successful laser treatment may provide an opportunity for monitoring disease progression or relapse via a blood sample.