Neuropilin-1 is required for endothelial cell adhesion to soluble vascular endothelial growth factor receptor 1

CX3CL1 (Fractalkine)-CX3CR1 Axis in Inflammation-Induced Angiogenesis and Tumorigenesis

The chemotactic cytokine fractalkine (FKN, chemokine CX3CL1) has unique properties resulting from the combination of chemoattractants and adhesion molecules. The soluble form (sFKN) has chemotactic properties and strongly attracts T cells and monocytes. The membrane-bound form (mFKN) facilitates diapedesis and is responsible for cell-to-cell adhesion, especially by promoting the strong adhesion of leukocytes (monocytes) to activated endothelial cells with the subsequent formation of an extracellular matrix and angiogenesis. FKN signaling occurs via CX3CR1, which is the only known member of the CX3C chemokine receptor subfamily. Signaling within the FKN-CX3CR1 axis plays an important role in many processes related to inflammation and the immune response, which often occur simultaneously and overlap. FKN is strongly upregulated by hypoxia and/or inflammation-induced inflammatory cytokine release, and it may act locally as a key angiogenic factor in the highly hypoxic tumor microenvironment. The importance of the FKN/CX3CR1 signaling pathway in tumorigenesis and cancer metastasis results from its influence on cell adhesion, apoptosis, and cell migration. This review presents the role of the FKN signaling pathway in the context of angiogenesis in inflammation and cancer. The mechanisms determining the pro- or anti-tumor effects are presented, which are the cause of the seemingly contradictory results that create confusion regarding the therapeutic goals.

Insight into the mechanism of CD34+ cell mobilisation impairment in multiple myeloma patients treated with anti-CD38 therapy

Induction therapy followed by CD34+ cell mobilisation and autologous transplantation represents standard of care for multiple myeloma (MM). However, the anti-CD38 monoclonal antibodies daratumumab and isatuximab have been associated with mobilisation impairment, yet the mechanism remains unclear. In this study, we investigated the effect of three different regimens (dara-VCd, isa-KRd and VTd) on CD34+ cells using flow cytometry and transcriptomics. Decreased CD34+ cell peak concentration and yields, longer collection and delayed engraftment were reproduced after dara-VCd/isa-KRd versus VTd induction in 34 patients in total. Using flow cytometry, we detected major changes in the proportion of apheresis product and bone marrow CD34+ subsets in patients treated with regimens containing anti-CD38 therapy; however, without any decrease in CD38high B-lymphoid progenitors in both materials. RNA-seq of mobilised CD34+ cells from 21 patients showed that adhesion genes are overexpressed in CD34+ cells after dara-VCd/isa-KRd and JCAD, NRP2, MDK, ITGA3 and CLEC3B were identified as potential target genes. Finally, direct in vitro effect of isatuximab in upregulating JCAD and CLEC3B was confirmed by quantitative PCR. These findings suggest that upregulated adhesion-related interactions, rather than killing of CD34+ cells by effector mechanisms, could be leading causes of decreased mobilisation efficacy in MM patients treated with anti-CD38 therapy.

Common mechanisms underlying diabetic vascular complications: focus on the interaction of metabolic disorders, immuno-inflammation, and endothelial dysfunction

Diabetic vascular complications (DVCs), including macro- and micro- angiopathy, account for a high percentage of mortality in patients with diabetes mellitus (DM). Endothelial dysfunction is the initial and role step for the pathogenesis of DVCs. Hyperglycemia and lipid metabolism disorders contribute to endothelial dysfunction via direct injury of metabolism products, crosstalk between immunity and inflammation, as well as related interaction network. Although physiological and phenotypic differences support their specified changes in different targeted organs, there are still several common mechanisms underlying DVCs. Also, inhibitors of these common mechanisms may decrease the incidence of DVCs effectively. Thus, this review may provide new insights into the possible measures for the secondary prevention of DM. And we discussed the current limitations of those present preventive measures in DVCs research. Video Abstract.

The Nervous System Development Regulator Neuropilin-1 as a Potential Prognostic Marker and Therapeutic Target in Brain Cancer

Neuropilins are transmembrane glycoproteins that regulate developmental processes in the nervous system and other tissues. Overexpression of neuropilin-1 (NRP1) occurs in many solid tumor types and, in several instances, may predict patient outcome in terms of overall survival. Experimental inhibition of NRP1 activity can display antitumor effects in different cancer models. Here, we review NRP1 expression and function in adult and pediatric brain cancers, particularly glioblastomas (GBMs) and medulloblastomas, and present analyses of NRP1 transcript levels and their association with patient survival in GBMs. The case of NRP1 highlights the potential of regulators of neurodevelopment as biomarkers and therapeutic targets in brain cancer.

Systematic pan-cancer analysis identified neuropilin 1 as an immunological and prognostic biomarker

Neuropilin 1 (NRP1) is a transmembrane glycoprotein, nontyrosine kinase receptor that plays an important role in axonal growth and angiogenesis in the nervous system. Although currently more and more studies have shown that NRP1 plays an important role in some cancers, no systematic pan-cancer analysis of NRP-1 has been performed to date. Therefore, we aimed to investigate the associated immune function and prognostic value of NRP1 in 33 tumors of various cancer types. In this study, based on The Cancer Genome Atlas, Cancer Cell Line Encyclopedia, Genotype Tissue Expression, cBioportal for cancer genomics, and Human Protein Atlas (HPA databases), various bioinformatics analysis methods were used to investigate the potential carcinogenic effects of NRP1 activation, pan-cancer analysis of NRP1 expression, and the relationship between NRP1 expression and prognosis indicators including overall survival, disease-specific survival, disease-free interval, and progression-free interval, tumor mutational burden (TMB), and microsatellite instability (MSI). The results showed that NRP1 was highly expressed in most tumors. In addition, NRP1 was found to be positively or negatively correlated with the prognosis of different tumors. Also, the expression of NRP1 was associated with TMB and MSI in in 27 and 21 different types of tumors, respectively, and with DNA methylation in almost all the various types of tumors. The expression of the NRP1 gene was negatively correlated with the infiltration levels of most immune cells. In addition, the correlation between the level of immune cell infiltration and NRP1 expression varied according to immune cell subtype. Our study suggests that NRP1 plays an important role in tumor development and tumor immunity and could potentially be used as a prognostic indicator in a variety of malignancies.

The Endothelial Glycocalyx as a Target of Excess Soluble Fms-like Tyrosine Kinase-1

Soluble fms-like tyrosine kinase-1 (sFlt-1) is a secreted protein that binds heparan sulfate expressed on the endothelial glycocalyx (eGC). In this paper we analyze how excess sFlt-1 causes conformational changes in the eGC, leading to monocyte adhesion, a key event triggering vascular dysfunction. In vitro exposure of primary human umbilical vein endothelial cells to excess sFlt-1 decreased eGC height and increased stiffness as determined by atomic force microscopy (AFM). Yet, structural loss of the eGC components was not observed, as indicated by Ulex europaeus agglutinin I and wheat germ agglutinin staining. Moreover, the conformation observed under excess sFlt-1, a collapsed eGC, is flat and stiff with unchanged coverage and sustained content. Functionally, this conformation increased the endothelial adhesiveness to THP-1 monocytes by about 35%. Heparin blocked all these effects, but the vascular endothelial growth factor did not. In vivo administration of sFlt-1 in mice also resulted in the collapse of the eGC in isolated aorta analyzed ex vivo by AFM. Our findings show that excess sFlt-1 causes the collapse of the eGC and favors leukocyte adhesion. This study provides an additional mechanism of action by which sFlt-1 may cause endothelial dysfunction and injury.

Impaired VEGF-A-Mediated Neurovascular Crosstalk Induced by SARS-CoV-2 Spike Protein: A Potential Hypothesis Explaining Long COVID-19 Symptoms and COVID-19 Vaccine Side Effects?

Long coronavirus disease-19 (COVID-19) is a newly discovered syndrome characterized by multiple organ manifestations that persist for weeks to months, following the recovery from acute disease. Occasionally, neurological and cardiovascular side effects mimicking long COVID-19 have been reported in recipients of COVID-19 vaccines. Hypothetically, the clinical similarity could be due to a shared pathogenic role of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spike (S) protein produced by the virus or used for immunization. The S protein can bind to neuropilin (NRP)-1, which normally functions as a coreceptor for the vascular endothelial growth factor (VEGF)-A. By antagonizing the docking of VEGF-A to NRP-1, the S protein could disrupt physiological pathways involved in angiogenesis and nociception. One consequence could be the increase in unbound forms of VEGF-A that could bind to other receptors. SARS-CoV-2-infected individuals may exhibit increased plasma levels of VEGF-A during both acute illness and convalescence, which could be responsible for diffuse microvascular and neurological damage. A few studies suggest that serum VEGF-A may also be a potential biomarker for long COVID-19, whereas evidence for COVID-19 vaccines is lacking and merits further investigation.

The Anti-Vascular Endothelial Growth Factor Receptor 1 (VEGFR-1) D16F7 Monoclonal Antibody Inhibits Melanoma Adhesion to Soluble VEGFR-1 and Tissue Invasion in Response to Placenta Growth Factor

Placenta growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family involved in tumor-associated angiogenesis and melanoma invasion of the extra-cellular matrix (ECM) through activation of membrane VEGF receptor 1 (VEGFR-1). A soluble VEGFR-1 (sVEGFR-1) form is released in the ECM, where it sequesters proangiogenic factors and stimulates endothelial or tumor cell adhesion and chemotaxis through interaction with α5β1 integrin. The anti-VEGFR-1 monoclonal antibody (D16F7 mAb) inhibits VEGF-A or PlGF-mediated signal transduction without affecting ligand interaction, thus preserving sVEGFR-1 decoy function. The aim of this study was to investigate whether D16F7 mAb hampers melanoma spread by in vitro analysis of cell adhesion to sVEGFR-1, ECM invasion, transmigration through an endothelial cell monolayer and in vivo evaluation of tumor infiltrative potential in a syngeneic murine model. Results indicate that D16F7 mAb significantly inhibits melanoma adhesion to sVEGFR-1 and ECM invasion, as well as transmigration in response to PlGF. Moreover, treatment of melanoma-bearing mice with the anti-VEGFR-1 mAb not only inhibits tumor growth but also induces a significant reduction in bone infiltration associated with a decrease in PlGF-positive melanoma cells. Furthermore, D16F7 mAb reduces PlGF production by melanoma cells. Therefore, blockade of PLGF/VEGFR-1 signaling represents a suitable strategy to counteract the metastatic potential of melanoma.