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Vascular endothelial growth factors (VEGFs) regulate blood and lymph vessel formation through activation of three receptor tyrosine kinases, VEGFR-1, -2, and -3. The extracellular domain of VEGF receptors consists of seven immunoglobulin homology domains, which, upon ligand binding, promote receptor dimerization. Dimerization initiates transmembrane signaling, which activates the intracellular tyrosine kinase domain of the receptor. VEGF-C stimulates lymphangiogenesis and contributes to pathological angiogenesis via VEGFR-3. However, proteolytically processed VEGF-C also stimulates VEGFR-2, the predominant transducer of signals required for physiological and pathological angiogenesis. Here we present the crystal structure of VEGF-C bound to the VEGFR-2 high-affinity-binding site, which consists of immunoglobulin homology domains D2 and D3. This structure reveals a symmetrical 2:2 complex, in which left-handed twisted receptor domains wrap around the 2-fold axis of VEGF-C. In the VEGFs, receptor specificity is determined by an N-terminal alpha helix and three peptide loops. Our structure shows that two of these loops in VEGF-C bind to VEGFR-2 subdomains D2 and D3, while one interacts primarily with D3. Additionally, the N-terminal helix of VEGF-C interacts with D2, and the groove separating the two VEGF-C monomers binds to the D2/D3 linker. VEGF-C, unlike VEGF-A, does not bind VEGFR-1. We therefore created VEGFR-1/VEGFR-2 chimeric proteins to further study receptor specificity. This biochemical analysis, together with our structural data, defined VEGFR-2 residues critical for the binding of VEGF-A and VEGF-C. Our results provide significant insights into the structural features that determine the high affinity and specificity of VEGF/VEGFR interactions.

Angiogenesis and lymphangiogenesis are classical features of granuloma formation in pulmonary tuberculosis (PTB). In addition, the angiogenic factor--VEGF-A is a known biomarker for PTB. To examine the association of circulating angiogenic factors with PTB, we examined the systemic levels of VEGF-A, VEGF-C, VEGF-D, VEGF-R1, VEGF-R2 and VEGF-R3in individuals with PTB, latent TB (LTB) or no TB infection (NTB). Circulating levels of VEGF-A, VEGF-C andVEGF-R2 were significantly higher in PTB compared to LTB or NTB individuals. Moreover, the levels of VEGF-A, VEGF-C and VEGF-R2 were significantly higher in PTB with bilateral and/or cavitary disease. The levels of these factors also exhibited a significant positive relationship with bacterial burdens in PTB. ROC analysis revealed VEGF-A and VEGF-R2 as markers distinguishing PTB from LTB or NTB. Finally, the circulating levels of all the angiogenic factors examined were significantly reduced following successful chemotherapy. Therefore, our data demonstrate that PTB is associated with elevated levels of circulating angiogenic factors, possibly reflecting vascular and endothelial dysfunction. In addition, some of these circulating angiogenic factors could prove useful as biomarkers to monitor disease severity, bacterial burden and therapeutic responses.

To identify pre/perioperative variables that shape endothelial cell loss (ECL) after uncomplicated Descemet membrane endothelial keratoplasty (DMEK). This retrospective study included all consecutive patients with Fuchs endothelial corneal dystrophy who underwent DMEK surgery without perioperative or postoperative complications in 2015-2023 and were followed for 12 months. To identify covariates that predicted 12-month ECL, primary hierarchical multivariable analysis was conducted with 12 variables: patient age and sex; donor age; preoperative axial length, visual acuity, central corneal thickness, and graft endothelial cell density; endotamponade with sulfur hexafluoride (SF6) or air; triple-DMEK or pseudophakic-DMEK; operative time; graft marking; and rebubbling. 137 eyes (112 patients) were included. Multivariable analysis showed that SF6 predicted 13.6 ± 3.4% greater ECL vs. air (p < 0.0001) and accounted for 10% of total ECL variation. Longer operative time and multiple (≥2) rebubbling also predicted 0.4 ± 0.7% (p = 0.046) and 11.7 ± 5.1% (p = 0.02) higher ECL, respectively. SF6 significantly reduced rebubbling on univariable analysis (13% vs. 41% for air, p = 0.01). SF6 use for endotamponade may increase ECL after DMEK. There is an urgent need for randomized controlled trials that estimate the relative disadvantages (endothelial toxicity) and advantages (less bothersome rebubbling) of SF6. ClinicalTrials.gov Identifier: NCT02535819.

Alzheimer’s disease (AD) is a common disorder of progressive cognitive decline among elderly subjects. Angiogenesis-related factors including vascular endothelial growth factor (VEGF) might be involved in the pathogenesis of AD. Soluble form of the VEGF receptor is likely to be an intrinsic negative counterpart of VEGF. We measured the plasma levels of VEGF and its two soluble receptors (sVEGFR1 and sVEGFR2) in 120 control subjects, 75 patients with mild cognitive impairment, and 76 patients with AD using ELISA. Plasma levels of VEGF in patients with AD were higher than those in healthy control subjects. However, plasma levels of sVEGFR1 and sVEGFR2 were lower in patients with AD than in healthy control subjects. Levels of VEGFR2 mRNA were significantly decreased in human umbilical vein endothelial cells after amyloid-beta treatment. Further, protein levels of VEGFR2 were also decreased in the brains of AD model mice. In addition, we show that the expression of sVEGFR2 and VEGFR2 was also decreased by the transfection with the Notch intracellular domain. These results indicate that the alterations of VEGF and its two receptors levels might be associated with those at risk for Alzheimer’s disease.

Angiogenesis, the growth of new blood vessels, involves specification of endothelial cells to tip cells and stalk cells, which is controlled by Notch signalling, whereas vascular endothelial growth factor receptor (VEGFR)-2 and VEGFR-3 have been implicated in angiogenic sprouting. Surprisingly, we found that endothelial deletion of Vegfr3 , but not VEGFR-3-blocking antibodies, postnatally led to excessive angiogenic sprouting and branching, and decreased the level of Notch signalling, indicating that VEGFR-3 possesses passive and active signalling modalities. Furthermore, macrophages expressing the VEGFR-3 and VEGFR-2 ligand VEGF-C localized to vessel branch points, and Vegfc heterozygous mice exhibited inefficient angiogenesis characterized by decreased vascular branching. FoxC2 is a known regulator of Notch ligand and target gene expression, and Foxc2 +/− ; Vegfr3 +/− compound heterozygosity recapitulated homozygous loss of Vegfr3 . These results indicate that macrophage-derived VEGF-C activates VEGFR-3 in tip cells to reinforce Notch signalling, which contributes to the phenotypic conversion of endothelial cells at fusion points of vessel sprouts. Notch and VEGF signalling controls the specification of endothelial cells to tip and stalk cells during angiogenesis sprouting. Alitalo and colleagues show that macrophage-derived VEGF-C activates VEGFR2 to contribute to the conversion of endothelial cells from a tip- to a stalk-cell fate when two sprouts fuse to ensure vessel growth and branching.

Pharmacological inhibition of VEGF-A has proven to be effective in inhibiting angiogenesis and vascular leak associated with cancers and various eye diseases. However, little information is currently available on the binding kinetics and relative biological activity of various VEGF inhibitors. Therefore, we have evaluated the binding kinetics of two anti-VEGF antibodies, ranibizumab and bevacizumab, and VEGF Trap (also known as aflibercept), a novel type of soluble decoy receptor, with substantially higher affinity than conventional soluble VEGF receptors. VEGF Trap bound to all isoforms of human VEGF-A tested with subpicomolar affinity. Ranibizumab and bevacizumab also bound human VEGF-A, but with markedly lower affinity. The association rate for VEGF Trap binding to VEGF-A was orders of magnitude faster than that measured for bevacizumab and ranibizumab. Similarly, in cell-based bioassays, VEGF Trap inhibited the activation of VEGFR1 and VEGFR2, as well as VEGF-A induced calcium mobilization and migration in human endothelial cells more potently than ranibizumab or bevacizumab. Only VEGF Trap bound human PlGF and VEGF-B, and inhibited VEGFR1 activation and HUVEC migration induced by PlGF. These data differentiate VEGF Trap from ranibizumab and bevacizumab in terms of its markedly higher affinity for VEGF-A, as well as its ability to bind VEGF-B and PlGF.

Aflibercept is a recombinant fusion protein that acts as a soluble decoy receptor for vascular endothelial growth factor (VEGF), a key regulator of angiogenesis. It binds to all isoforms of VEGF-A as well as VEGF-B and placental growth factor, and, thus, prevents them from binding to and activating their cognate receptors. In the USA and EU, intravenously administered aflibercept in combination with an infusion of leucovorin, fluorouracil and irinotecan (FOLFIRI) is approved for the treatment of patients with metastatic colorectal cancer that is resistant to or has progressed after treatment with an oxaliplatin-containing regimen. The efficacy of aflibercept in this indication was assessed in a multinational, pivotal phase 3 trial (VELOUR), in which the approved regimen of aflibercept 4 mg/kg every 2 weeks plus FOLFIRI significantly prolonged median overall survival by 1.44 months compared with FOLFIRI alone (primary endpoint). The addition of aflibercept also significantly prolonged progression-free survival and significantly increased the objective response rate compared with FOLFIRI alone. Addition of aflibercept to FOLFIRI was associated with anti-VEGF-related adverse events and an increased incidence of FOLFIRI-related adverse events, but the tolerability of the combination was generally acceptable in this pre-treated population. The most common grade 3 or 4 adverse events with aflibercept plus FOLFIRI included neutropenia, diarrhoea and hypertension. In conclusion, aflibercept plus FOLFIRI is a useful treatment option for patients with metastatic colorectal cancer previously treated with an oxaliplatin-containing regimen, with or without bevacizumab.

During tumor growth, angiogenesis is required to ensure oxygen and nutrient transport to the tumor. Vascular endothelial growth factor (VEGF) is the major inducer of angiogenesis and appears to be a key modulator of the anti-tumor immune response. Indeed, VEGF modulates innate and adaptive immune responses through direct interactions and indirectly by modulating protein expressions on endothelial cells or vascular permeability. The inhibition of the VEGF signaling pathway is clinically approved for the treatment of several cancers. Therapies targeting VEGF can modulate the tumor vasculature and the immune response. In this review, we discuss the roles of VEGF in the anti-tumor immune response. In addition, we summarize therapeutic strategies based on its inhibition, and their clinical approval.

DLL4–Notch signalling suppresses endothelial sprouting and angiogenic growth through crosstalk with the vascular endothelial growth factor (VEGF) pathway; VEGF receptor 2 has been thought to have a crucial role in this crosstalk, but now VEGF receptor 3 is shown to be the more important modulator. VEGFR3 and angiogenesis control DLL4–Notch signalling suppresses endothelial sprouting and angiogenic growth through crosstalk with the VEGF pathway. The current widely accepted model for how this crosstalk operates proposes a crucial role for VEGFR2. It is thought that DLL4 expression in tip cells is induced by the actions of VEGF-A on VEGFR2, and that subsequent Notch signalling in stalk cells suppresses VEGFR2 and VEGFR3 transcription, which prevents these cells from adopting tip-cell behaviour. Benedito et al . now show that this model needs to be revised. They show that DLL4 protein expression in tip cells is only weakly modulated by VEGFR2 signalling, and that Notch inhibition can induce endothelial sprouting even in the absence of VEGFR2. They further find that Notch inhibition has little impact on VEGFR2 transcription, but strongly modulates VEGFR3, the main receptor for VEGFC, and that VEGFR3 kinase inhibition, but not VEGFR3 ligand-binding antibodies, suppresses the sprouting of endothelial cells with low Notch signalling. Their findings may help to explain why some patients treated with VEGF-A inhibitors for cancer and age-related macular degeneration do not respond to this therapy, and the work suggests that investigating the status of vascular Notch or VEGFR3 activation might provide clues for more effective therapies. Developing tissues and growing tumours produce vascular endothelial growth factors (VEGFs), leading to the activation of the corresponding receptors in endothelial cells. The resultant angiogenic expansion of the local vasculature can promote physiological and pathological growth processes 1 . Previous work has uncovered that the VEGF and Notch pathways are tightly linked. Signalling triggered by VEGF-A (also known as VEGF) has been shown to induce expression of the Notch ligand DLL4 in angiogenic vessels and, most prominently, in the tip of endothelial sprouts 2 , 3 . DLL4 activates Notch in adjacent cells, which suppresses the expression of VEGF receptors and thereby restrains endothelial sprouting and proliferation 2 , 4 , 5 , 6 . Here we show, by using inducible loss-of-function genetics in combination with inhibitors in vivo , that DLL4 protein expression in retinal tip cells is only weakly modulated by VEGFR2 signalling. Surprisingly, Notch inhibition also had no significant impact on VEGFR2 expression and induced deregulated endothelial sprouting and proliferation even in the absence of VEGFR2, which is the most important VEGF-A receptor and is considered to be indispensable for these processes. By contrast, VEGFR3, the main receptor for VEGF-C, was strongly modulated by Notch. VEGFR3 kinase-activity inhibitors but not ligand-blocking antibodies suppressed the sprouting of endothelial cells that had low Notch signalling activity. Our results establish that VEGFR2 and VEGFR3 are regulated in a highly differential manner by Notch. We propose that successful anti-angiogenic targeting of these receptors and their ligands will strongly depend on the status of endothelial Notch signalling.

A trial of three drugs — bevacizumab, ranibizumab, and aflibercept — for the treatment of diabetic macular edema showed that each drug improved visual acuity, but aflibercept outperformed the other two drugs for eyes with a baseline visual acuity of 20/50 or worse. Diabetic macular edema, a manifestation of diabetic retinopathy that impairs central vision, affects approximately 750,000 people in the United States and is a leading cause of vision loss. 1 The costs associated with visual disability and treatment of diabetic macular edema are high. 2 The increasing prevalence of diabetes worldwide highlights the importance of diabetic macular edema as a global health issue. 3 Vascular endothelial growth factor (VEGF) is an important mediator of abnormal vascular permeability in diabetic macular edema. 4 , 5 Intravitreous injections of anti-VEGF agents have been shown to be superior to laser photocoagulation of the macula, the standard treatment for diabetic . . .