Targeting VEGF signalling via the neuropilin co-receptor

Single-nucleus RNA sequencing reveals distinct pathophysiological trophoblast signatures in spontaneous preterm birth subtypes

Spontaneous preterm birth (sPTB) poses significant challenges, affecting neonatal health and neurodevelopmental outcomes worldwide. The specific effects of placental trophoblasts on the pathological development of sPTB subtypes-preterm premature rupture of fetal membranes (pPROM) and spontaneous preterm labor (sPTL)-are not fully understood, making it crucial to uncover these impacts for the development of effective therapeutic strategies. Using single-nucleus RNA sequencing, we investigated transcriptomic and cellular differences at the maternal-fetal interface in pPROM and sPTL placentas. Our findings revealed distinct trophoblast compositions with pPROM characterized predominantly by extravillous trophoblasts (EVTs), while sPTL showed an abundance of syncytiotrophoblasts (STBs). Through cell differentiation and cell-to-cell communication analyses, other distinguishing factors were also found. In pPROM, heightened inflammation, oxidative stress, and vascular dysregulation with key pathways including tumor necrosis factor signaling, matrix metalloproteinase activation, and integrin-mediated cell adhesion, highlighted an invasive EVT profile potentially driven by hypoxic conditions and immune cell recruitment. In contrast, sPTL was marked by increased smooth muscle contraction, vascular remodeling, and altered signaling dynamics involving fibroblasts, including TGF-β and WNT pathways. Our study highlights the critical need to distinguish sPTB subtypes to improve diagnostic precision and therapeutic targeting. The molecular insights gained provide a foundation for future investigations aimed at functional validation of key pathways and exploration of trophoblasts on the development of sPTB. Ultimately, these findings pave the way for more personalized and effective interventions to mitigate adverse outcomes associated with preterm birth.

Role of semaphorins, neuropilins and plexins in cancer progression

Progress in understanding nervous system-cancer interconnections has emphasized the functional role of semaphorins (SEMAs) and their receptors, neuropilins (NRPs) and plexins (PLXNs), in cancer progression. SEMAs are a conserved and extensive family of broadly expressed soluble and membrane-associated proteins that were first described as regulators of axon guidance and neural and vascular development. However, recent advances have shown that they can have a dual role in cancer progression, acting either as tumor promoters or suppressors. SEMAs effects result from their interaction with specific co-receptors/receptors NRPs/PLXNs, that have also been described to play a role in cancer progression. They can influence both cancer cells and tumor microenvironment components modulating various aspects of tumorigenesis such as oncogenesis, tumor growth, invasion and metastatic spread or treatment resistance. In this review we focus on the role of these axon guidance signals and their receptors and co-receptors in various aspects of cancer. Furthermore, we also highlight their potential application as novel approaches for cancer treatment in the future.

NRP1 antagonism as a novel therapeutic target in nasal polyps of patients with chronic rhinosinusitis

BACKGROUND

Neuropilin-1 (NRP1) is expressed on the surface epithelium of respiratory tract and immune cells, demonstrating its possible function in regulating the immune response in airway disease. However, its role in patient with chronic rhinosinusitis (CRS) remains unknown. This study aimed to elucidate the role of NRP1 in CRS with nasal polyps (CRSwNP).

METHODS

Sinonasal biopsy specimens were immunohistochemically stained to investigate NRP1 expression. Double immunofluorescence, immunoblotting, and real-time polymerase chain reaction were performed to evaluate NRP1 in primary human nasal epithelial cells (hNECs). An NRP1 inhibitor was administered to a murine nasal polyp (NP) model.

RESULTS

NRP1 was highly expressed in the epithelium in patients with CRSwNP compared to nasal tissue from controls and CRS without NP patients. NRP1 and vascular endothelial growth factor were upregulated in hNECs under hypoxia. Treatment with NRP1 inhibitor (EG00229) reduced the secretion of interleukin (IL)-1β, IL-6, IL-8, and IL-33 cytokines, as well as inducible nitric oxide synthase, cyclooxygenase-2, and prostaglandin E2 in hNECs. We found that NRP1 was highly expressed in the airway epithelium in the murine NP model. The group treated with the NRP1 inhibitor had significantly fewer nasal polypoid lesions and reduced accumulations of immune cells.

CONCLUSIONS

These findings reveal that NRP1 is upregulated in CRS and NP epithelium, and the inhibition of NRP1 may lead to a reduction in NP growth and immune cell infiltration. Our results suggest that NRP1 inhibition could be a novel possibility for treating nasal polyposis.

NRP1 knockdown inhibits the invasion and migration of rhabdoid tumor of the kidney cells

PURPOSE

The aim of this study was to detect candidate oncogenes of rhabdoid tumor of the kidney (RTK) and evaluate their roles in RTK in vitro.

METHODS

An integrated analysis of messenger RNA (mRNA) and microRNA (miRNA) sequencing was performed to determine the expression profile of exosome-derived miRNAs and mRNAs in human RTK-derived cell lines and a human embryonic renal cell line. A Gene Ontology enrichment analysis was performed to analyze the functional characteristics of differentially expressed mRNAs in RTK cells. Matrigel invasion and wound-healing assays were performed to evaluate the cell invasion and migration abilities.

RESULTS

Forty mRNAs were highly expressed in RTK cells targeted by exosomal miRNAs, the expression of which was lower in RTK cells than in the controls. These mRNAs were primarily related to cell adhesion. Of these mRNAs, we selected neuropilin 1 (NRP1) as a candidate oncogene because its upregulated expression is associated with a poor prognosis of several types of tumors. RTK cells in which NRP1 had been knocked down exhibited decreased invasive and migratory abilities.

CONCLUSION

Our study indicates that NRP1 acts as an oncogene by promoting the invasion and migration of RTK cells and that it could serve as a therapeutic target.

Targeting tumor-infiltrating tregs for improved antitumor responses

Immunotherapies have revolutionized the landscape of cancer treatment. Regulatory T cells (Tregs), as crucial components of the tumor immune environment, has great therapeutic potential. However, nonspecific inhibition of Tregs in therapies may not lead to enhanced antitumor responses, but could also trigger autoimmune reactions in patients, resulting in intolerable treatment side effects. Hence, the precision targeting and inhibition of tumor-infiltrating Tregs is of paramount importance. In this overview, we summarize the characteristics and subpopulations of Tregs within tumor microenvironment and their inhibitory mechanisms in antitumor responses. Furthermore, we discuss the current major strategies targeting regulatory T cells, weighing their advantages and limitations, and summarize representative clinical trials targeting Tregs in cancer treatment. We believe that developing therapies that specifically target and suppress tumor-infiltrating Tregs holds great promise for advancing immune-based therapies.

Targeting SARS-CoV-2 entry processes: The promising potential and future of host-targeted small-molecule inhibitors

The COVID-19 pandemic, caused by SARS-CoV-2, has had a huge impact on global health. To respond to rapidly mutating viruses and to prepare for the next pandemic, there is an urgent need to develop small molecule therapies that target critical stages of the SARS-CoV-2 life cycle. Inhibiting the entry process of the virus can effectively control viral infection and play a role in prevention and treatment. Host factors involved in this process, such as ACE2, TMPRSS2, ADAM17, furin, PIKfyve, TPC2, CTSL, AAK1, V-ATPase, HSPG, and NRP1, have been found to be potentially good targets with stability. Through further exploration of the cell entry process of SARS-CoV-2, small-molecule drugs targeting these host factors have been developed. This review focuses on the structural functions of potential host cell targets during the entry of SARS-CoV-2 into host cells. The research progress, chemical structure, structure-activity relationship, and clinical value of small-molecule inhibitors against COVID-19 are reviewed to provide a reference for the development of small-molecule drugs against COVID-19.

VEGF/Nrp1/HIF-1α promotes proliferation of hepatocellular carcinoma through a positive feedback loop

To investigate the role of neuropilin1 (Nrp1) in glucose metabolism and proliferation of hepatocellular carcinoma (HCC) cells and to analyze its mechanism of action. The CRISPR gene knockout technique was used to knock out the Nrp1 gene in two HCC cell lines. The effect of Nrp1 on the proliferation of HCC cells was assessed in the CCK8 assay and plate cloning assay. The expression levels of glucose consumption, lactate production, and essential proteins of the glycolytic pathway were detected to explore the effect of Nrp1 on glucose metabolism in HCC cells. Using CoCl2 to revert the expression of hypoxia inducible factor-1α (HIF-1α), the role of HIF-1α in the pro-HCC cell metabolism of Nrp1 were demonstrated. The protein synthesis inhibitor CHX and proteasome inhibitor MG-132 was used to analyze the molecular mechanism of action of Nrp1 on HIF-1α. The Kaplan-Meier method was used to calculate survival rates and plot survival curves. Based on the CCK8 assay and plate cloning assay, we found that Nrp1 knockout significantly inhibited the proliferation of HCC cells. Nrp1 inhibitor suppressed lactate production and glucose consumption in HCC cells. Knockout of Nrp1 decreased the expression of glycolytic pathway-related proteins and HIF-1α protein. Furthermore, by joint use of CoCl2 and NRP1 knockout, we confirmed that reverting HIF-1α expression could reverse the effect of Nrp1 knockout on HCC cell metabolism in vitro. Mechanistically, Nrp1 showed a close correlation with the stability of HIF-1α protein in protein stability assay. Finally, we revealed that high expression of Nrp1 in HCC tissues was associated with poor overall survival and disease-free survival of the patients. Nrp1 accelerates glycolysis and promotes proliferation of HCC by regulating HIF-1α protein stability and through the VEGF/Nrp1/HIF-1α positive feedback loop.

Deciphering the heterogeneity and immunosuppressive function of regulatory T cells in osteosarcoma using single-cell RNA transcriptome

Osteosarcoma (OS) is a highly invasive malignant neoplasm with poor prognosis. The tumor microenvironment (TME) plays an essential role in the occurrence and development of OS. Regulatory T cells (Tregs) are known to facilitate immunosuppression, tumor progression, invasion, and metastasis. However, the effect of Tregs in the TME of OS remains unclear. In this study, single-cell RNA sequencing (scRNA-seq) data was used to identify Tregs and various other cell clusters in the TME of OS. Gene set variation analysis (GSVA) was used to investigate the signaling pathways in Tregs from OS and adjacent tissues. The CellChat and iTALK packages were used to analyze cellular communication. In addition, a prognostic model was established based on the Tregs-specific genes using bulk RNA-seq from the TARGET database, and it was verified using a Gene Expression Omnibus dataset. The pRRophetic package was used to predict drug sensitivity. Immunohistochemistry was used to verify the expression of candidate genes in OS. Based on the above methods, we showed that the OS samples were highly infiltrated with Tregs. GSVA revealed that oxidative phosphorylation, angiogenesis and mammalian target of rapamycin complex 1 (mTORC1) were highly activated in Tregs from OS compared with those from adjacent tissues. Using cellular communication analysis, we found that Tregs interacted with osteoblastic, endothelial, and myeloid cells via C-X-C motif chemokine ligand (CXCL) signaling; particularly, they strongly affected the expression of C-X-C motif chemokine receptor 4 (CXCR4) and interacted with other cell clusters through CXCL12/transforming growth factor β1 (TGFB1) to collectively enable tumor growth and progression. Subsequently, two Tregs-specific genes-CD320 and MAF-were screened through univariate, least absolute shrinkage and selection operator regression (LASSO) and multivariate analysis to construct a prognostic model, which showed excellent prognostic accuracy in two independent cohorts. In addition, drug sensitivity analysis demonstrated that OS patients at high Tregs risk were sensitive to sunitinib, sorafenib, and axitinib. We also used immunohistochemistry to validate that CD320 and MAF were significantly upregulated in OS tissues compared with adjacent tissues. Overall, this study reveals the heterogeneity of Tregs in the OS TME, providing new insights into the invasion and treatment of this cancer.

High VEGF Concentrations Accelerate Human Trabecular Meshwork Fibrosis in a TAZ-Dependent Manner

We aimed to investigate the effects of different concentrations of vascular endothelial growth factor (VEGF) on the extracellular matrix (ECM) and fibrotic proteins in human trabecular meshwork (TM) cells. We also explored how the Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) signaling pathway modulates VEGF-induced fibrosis. We determined cross-linked actin network (CLAN) formation using TM cells. Changes in fibrotic and ECM protein expression were determined. High VEGF concentrations (10 and 30 ng/mL) increased TAZ and decreased p-TAZ/TAZ expression in TM cells. Western blotting and real-time PCR revealed no YAP expression changes. Fibrotic and ECM protein expression decreased at low VEGF concentrations (1 and 10 ρg/mL) and significantly increased at high VEGF concentrations (10 and 30 ng/mL). CLAN formation increased in TM cells treated with high VEGF concentrations. Moreover, TAZ inhibition by verteporfin (1 μM) rescued TM cells from high-VEGF-concentration-induced fibrosis. Low VEGF concentrations reduced fibrotic changes, whereas high VEGF concentrations accelerated fibrosis and CLAN formations in TM cells in a TAZ-dependent manner. These findings reflect the dose-dependent influences of VEGF on TM cells. Moreover, TAZ inhibition might be a therapeutic target for VEGF-induced TM dysfunction.

A Novel Blood-Brain Barrier-Penetrating and Vascular-Targeting Chimeric Peptide Inhibits Glioma Angiogenesis

The high vascularization of glioma highlights the potential value of anti-angiogenic therapeutics for glioma treatment. Previously, we designed a novel vascular-targeting and blood-brain barrier (BBB)-penetrating peptide, TAT-AT7, by attaching the cell-penetrating peptide TAT to a vascular-targeting peptide AT7, and we demonstrated that TAT-AT7 could target binding to the vascular endothelial growth factor receptor 2 (VEGFR-2) and Neuropilin-1 (NRP-1), which are both highly expressed in endothelial cells. TAT-AT7 has been proven to be a good targeting peptide which could effectively deliver the secretory endostatin gene to treat glioma via the TAT-AT7-modified polyethyleneimine (PEI) nanocomplex. In the current study, we further explored the molecular binding mechanisms of TAT-AT7 to VEGFR-2 and NRP-1 and its anti-glioma effects. Accordingly, TAT-AT7 was proven to competitively bind to VEGFR-2 and NRP-1 and prevent VEGF-A165 binding to the receptors by the surface plasmon resonance (SPR) assay. TAT-AT7 inhibited endothelial cells' proliferation, migration, invasion, and tubule formation, as well as promoted endothelial cells' apoptosis in vitro. Further research revealed that TAT-AT7 inhibited the phosphorylation of VEGFR-2 and its downstream PLC-γ, ERK1/2, SRC, AKT, and FAK kinases. Additionally, TAT-AT7 significantly inhibited angiogenesis of zebrafish embryo. Moreover, TAT-AT7 had a better penetrating ability and could penetrate the BBB into glioma tissue and target glioma neovascularization in an orthotopic U87-glioma-bearing nude mice model, and exhibited the effect of inhibiting glioma growth and angiogenesis. Taken together, the binding and function mechanisms of TAT-AT7 were firstly revealed, and TAT-AT7 was proven to be an effective and promising peptide for the development of anti-angiogenic drugs for targeted treatment of glioma.

Scandium-44: Diagnostic Feasibility in Tumor-Related Angiogenesis

Angiogenesis-related cell-surface molecules, including integrins, aminopeptidase N, vascular endothelial growth factor, and gastrin-releasing peptide receptor (GRPR), play a crucial role in tumour formation. Radiolabelled imaging probes targeting angiogenic biomarkers serve as valuable vectors in tumour identification. Nowadays, there is a growing interest in novel radionuclides other than gallium-68 (⁶⁸Ga) or copper-64 (⁶⁴Cu) to establish selective radiotracers for the imaging of tumour-associated neo-angiogenesis. Given its ideal decay characteristics (E_β⁺_average: 632 KeV) and a half-life (T_1/2 = 3.97 h) that is well matched to the pharmacokinetic profile of small molecules targeting angiogenesis, scandium-44 (⁴⁴Sc) has gained meaningful attention as a promising radiometal for positron emission tomography (PET) imaging. More recently, intensive research has been centered around the investigation of ⁴⁴Sc-labelled angiogenesis-directed radiopharmaceuticals. Previous studies dealt with the evaluation of ⁴⁴Sc-appended a_vb₃ integrin-affine Arg-Gly-Asp (RGD) tripeptides, GRPR-selective aminobenzoyl-bombesin analogue (AMBA), and hypoxia-associated nitroimidazole derivatives in the identification of various cancers using experimental tumour models. Given the tumour-related hypoxia- and angiogenesis-targeting capability of these PET probes, ⁴⁴Sc seems to be a strong competitor of the currently used positron emitters in radiotracer development. In this review, we summarize the preliminary preclinical achievements with ⁴⁴Sc-labelled angiogenesis-specific molecular probes.

Tumor-infiltrating regulatory T cells as targets of cancer immunotherapy

Regulatory T cells (Tregs) are abundant in tumor tissues, raising a question of whether immunosuppressive tumor-infiltrating Tregs (TI-Tregs) can be selectively depleted or functionally attenuated to evoke effective anti-tumor immune responses by conventional T cells (Tconvs), without perturbing Treg-dependent immune homeostasis in healthy organs and causing autoimmunity. Here, we review current cancer immunotherapy strategies, including immune checkpoint blockade (ICB) antibodies against CTLA-4 and PD-1 and discuss their effects on TI-Tregs. We also discuss approaches that exploit differentially regulated molecules on the cell surface (e.g., CTLA-4) and intracellularly (e.g., T cell receptor signaling molecules) between TI-Tregs and Tconvs as well as their dependence on cytokines (e.g., IL-2) and metabolites (e.g., lactate). We envisage that targeting TI-Tregs could be effective as a monotherapy and/or when combined with ICB antibodies.

Identification of Four New Chemical Series of Small Drug-Like Natural Products as Potential Neuropilin-1 Inhibitors by Structure-Based Virtual Screening: Pharmacophore-Based Molecular Docking and Dynamics Simulation

Neuropilin-1 (NRP-1), a surface transmembrane glycoprotein, is one of the most important co-receptors of VEGF-A165 (vascular endothelial growth factor) responsible for pathological angiogenesis. In general, NRP-1 overexpression in cancer correlates with poor prognosis and more tumor aggressiveness. NRP-1 role in cancer has been mainly explained by mediating VEGF-A165-induced effects on tumor angiogenesis. NRP-1 was recently identified as a co-receptor and an independent gateway for SARS-CoV-2 through binding subunit S2 of Spike protein in the same way as VEGF-A165. Thus, NRP-1 is of particular value as a target for cancer therapy and other angiogenesis-dependent diseases as well as for SARS-CoV-2 antiviral intervention. Herein, The Super Natural II, the largest available database of natural products (∼0.33 M), pre-filtered with drug-likeness criteria (absorption, distribution, metabolism and excretion/toxicity), was screened against NRP-1. NRP-1/VEGF-A165 interaction is one of protein-protein interfaces (PPIs) known to be challenging when approached in-silico. Thus, a PPI-suited multi-step virtual screening protocol, incorporating a derived pharmacophore with molecular docking and followed by MD (molecular dynamics) simulation, was designed. Two stages of pharmacophorically constrained molecular docking (standard and extra precisions), a mixed Torsional/Low-mode conformational search and MM-GBSA ΔG binding affinities calculation, resulted in the selection of 100 hits. These 100 hits were subjected to 20 ns MD simulation, that was extended to 100 ns for top hits (20) and followed by post-dynamics analysis (atomic ligand-protein contacts, RMSD, RMSF, MM-GBSA ΔG, Rg, SASA and H-bonds). Post-MD analysis showed that 19 small drug-like nonpeptide natural molecules, grouped in four chemical scaffolds (purine, thiazole, tetrahydropyrimidine and dihydroxyphenyl), well verified the derived pharmacophore and formed stable and compact complexes with NRP-1. The discovered molecules are promising and can serve as a base for further development of new NRP-1 inhibitors.

High expression of E2F transcription factors 7: An independent predictor of poor prognosis in patients with lung adenocarcinoma

Adenocarcinoma is the most common pathological type of lung cancer. The E2F7 transcription factor has been confirmed to be related to the occurrence and development of a variety of solid tumors, but the relationship with the prognosis of lung cancer is still unclear. Therefore, we conducted this study to explore the prognostic value of E2F7 for lung adenocarcinoma (LUAD) patients. In this study, we analyzed samples from the Cancer Genome Atlas (TCGA) to study the correlation between the expression of E2F7 and clinical features, the difference in expression between tumors and normal tissues, the prognostic and diagnostic value, and Enrichment analysis of related genes. All statistical analysis uses R statistical software (version 3.6.3). The result shows that the expression level of E2F7 in LUAD was significantly higher than that of normal lung tissue (P = 1e-34). High expression of E2F7 was significantly correlated with gender (P = .034), pathologic stage (P = .046) and M stage (P = .025). Multivariate Cox analysis confirmed that E2F7 is an independent risk factor for OS in LUAD patients (P = .027). Genes related to cell cycle checkpoints, DNA damage telomere stress-induced senescence, DNA methylation, chromosome maintenance and mitotic prophase showed differential enrichment in the E2F7 high expression group. In short, high expression of E2F7 is an independent risk factor for OS in LUAD patients and has a high diagnostic value.

The impact of sensory neuropathy and inflammation on epithelial wound healing in diabetic corneas

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes, with several underlying pathophysiological mechanisms, some of which are still uncertain. The cornea is an avascular tissue and sensitive to hyperglycemia, resulting in several diabetic corneal complications including delayed epithelial wound healing, recurrent erosions, neuropathy, loss of sensitivity, and tear film changes. The manifestation of DPN in the cornea is referred to as diabetic neurotrophic keratopathy (DNK). Recent studies have revealed that disturbed epithelial-neural-immune cell interactions are a major cause of DNK. The epithelium is supplied by a dense network of sensory nerve endings and dendritic cell processes, and it secretes growth/neurotrophic factors and cytokines to nourish these neighboring cells. In turn, sensory nerve endings release neuropeptides to suppress inflammation and promote epithelial wound healing, while resident immune cells provide neurotrophic and growth factors to support neuronal and epithelial cells, respectively. Diabetes greatly perturbs these interdependencies, resulting in suppressed epithelial proliferation, sensory neuropathy, and a decreased density of dendritic cells. Clinically, this results in a markedly delayed wound healing and impaired sensory nerve regeneration in response to insult and injury. Current treatments for DPN and DNK largely focus on managing the severe complications of the disease. Cell-based therapies hold promise for providing more effective treatment for diabetic keratopathy and corneal ulcers.

Mediating EGFR-TKI Resistance by VEGF/VEGFR Autocrine Pathway in Non-Small Cell Lung Cancer

NSCLC treatment includes targeting of EGFR with tyrosine kinase inhibitors (TKIs) such as Erlotinib; however, resistance to TKIs is commonly acquired through T790M EGFR mutations or overexpression of vascular endothelial growth factor receptor-2 (VEGFR-2). We investigated the mechanisms of EGFR-TKI resistance in NSCLC cell lines with EGFR mutations or acquired resistance to Erlotinib. These studies showed upregulated gene and protein expression of VEGF, VEGFR-2, and a VEGF co-receptor neuropilin-1 (NP-1) in Erlotinib-resistant (1.4-5.3-fold) and EGFR double-mutant (L858R and T790M; 4.1-8.3-fold) NSCLC cells compared to parental and EGFR single-mutant (L858R) NSCLC cell lines, respectively. Immunofluorescence and FACS analysis revealed increased expression of VEGFR-2 and NP-1 in EGFR-TKI-resistant cell lines compared to TKI-sensitive cell lines. Cell proliferation assays showed that treatment with a VEGFR-2 inhibitor combined with Erlotinib lowered cell survival in EGFR double-mutant NSCLC cells to 9% compared to 72% after treatment with Erlotinib alone. Furthermore, Kaplan-Meier analysis revealed shorter median survival in late-stage NSCLC patients with high vs. low VEGFR-2 expression (14 mos vs. 21 mos). The results indicate that VEGFR-2 may play a key role in EGFR-TKI resistance and that combined treatment of Erlotinib with a VEGFR-2 inhibitor may serve as an effective therapy in NSCLC patients with EGFR mutations.

Synthesis, Physicochemical and Biological Study of Gallium-68- and Lutetium-177-Labeled VEGF-A165/NRP-1 Complex Inhibitors Based on Peptide A7R and Branched Peptidomimetic

Neuropilin-1 (NRP-1) is a surface receptor found on many types of cancer cells. The overexpression of NRP-1 and its interaction with vascular endothelial growth factor-165 (VEGF₁₆₅) are associated with tumor growth and metastasis. Therefore, compounds that block the VEGF₁₆₅/NRP-1 interaction represent a promising strategy to image and treat NRP-1-related pathologies. The aim of the presented work was to design and synthesize radioconjugates of two known peptide-type inhibitors of the VEGF₁₆₅/NRP-1 complex: A7R peptide and its shorter analog, the branched peptidomimetic Lys(hArg)-Dab-Pro-Arg. Both peptide-type inhibitors were coupled to a radionuclide chelator (DOTA) via a linker (Ahx) and so radiolabeled with Ga-68 and Lu-177 radionuclides, for diagnostic and therapeutic uses, respectively. The synthesized radioconjugates were tested for their possible use as theranostic-like radiopharmaceuticals for the imaging and therapy of cancers that overexpress NRP-1. The obtained results indicate good efficiency of the radiolabeling reaction and satisfactory stability, at least 3t_1/2 for the ⁶⁸Ga- and 1t_1/2 for the ¹⁷⁷Lu-radiocompounds, in solutions mimicking human body fluids. However, enzymatic degradation of both the studied inhibitors caused insufficient stability of the radiocompounds in human serum, indicating that further modifications are needed to sufficiently stabilize the peptidomimetics with inhibitory properties against VEGF₁₆₅/NRP-1 complex formation.

A Structural Overview of Vascular Endothelial Growth Factors Pharmacological Ligands: From Macromolecules to Designed Peptidomimetics

The vascular endothelial growth factor (VEGF) family of cytokines plays a key role in vasculogenesis, angiogenesis, and lymphangiogenesis. VEGF-A is the main member of this family, alongside placental growth factor (PlGF), VEGF-B/C/D in mammals, and VEGF-E/F in other organisms. To study the activities of these growth factors under physiological and pathological conditions, resulting in therapeutic applications in cancer and age-related macular degeneration, blocking ligands have been developed. These have mostly been large biomolecules like antibodies. Ligands with high affinities, at least in the nanomolar range, and accurate structural data from X-ray crystallography and NMR spectroscopy have been described. They constitute the main focus of this overview, which evidences similarities and differences in their binding modes. For VEGF-A ligands, and to a limited extent also for PlGF, a transition is now observed towards developing smaller ligands like nanobodies and peptides. These include unnatural amino acids and chemical modifications for designed and improved properties, such as serum stability and greater affinity. However, this review also highlights the scarcity of such small molecular entities and the striking lack of small organic molecule ligands. It also shows the gap between the rather large array of ligands targeting VEGF-A and the general absence of ligands binding other VEGF members, besides some antibodies. Future developments in these directions are expected in the upcoming years, and the study of these growth factors and their promising therapeutic applications will be welcomed.

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

Neuropilin‐1 (NRP‐1) is a semaphorin receptor involved in neuron guidance, and a co‐receptor for selected isoforms of the vascular endothelial growth factor (VEGF) family. NRP‐1 binding to several VEGF‐A isoforms promotes growth factor interaction with VEGF receptor (VEGFR)‐2, increasing receptor phosphorylation. Additionally, NRP‐1 directly interacts with VEGFR‐1, but this interaction competes with NRP‐1 binding to VEGF‐A165 and does not enhance VEGFR‐1 activation. In this work, we investigated in detail the role of NRP‐1 interaction with the soluble isoform of VEGFR‐1 (sVEGFR‐1) in angiogenesis. sVEGFR‐1 acts both as a decoy receptor for VEGFs and as an extracellular matrix protein directly binding to α5β1 integrin on endothelial cells. By combining cell adhesion assays and surface plasmon resonance experiments on purified proteins, we found that sVEGFR‐1/NRP‐1 interaction is required both for α5β1 integrin binding to sVEGFR‐1 and for endothelial cell adhesion to a sVEGFR‐1‐containing matrix. We also found that a previously reported anti‐angiogenic peptide (Flt_2‐11), which maps in the second VEGFR‐1 Ig‐like domain, specifically binds NRP‐1 and inhibits NRP‐1/sVEGFR‐1 interaction, a process that likely contributes to its anti‐angiogenic activity. In view of potential translational applications, we developed a five‐residue‐long peptide, derived from Flt_2‐11, which has the same ability as the parent Flt_2‐11 peptide to inhibit cell adhesion to, and migration towards, sVEGFR‐1. Therefore, the Flt_2‐5 peptide represents a potential anti‐angiogenic compound per se, as well as an attractive lead for the development of novel angiogenesis inhibitors acting with a different mechanism with respect to currently used therapeutics, which interfere with VEGF‐A165 binding.

Neuropilin-1: A feasible link between liver pathologies and COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has a tremendous impact on the health of millions of people worldwide. Unfortunately, those suffering from previous pathological conditions are more vulnerable and tend to develop more severe disease upon infection with the new SARS-CoV-2. This coronavirus interacts with the angiotensin-converting enzyme 2 receptor to invade the cells. Recently, another receptor, neuropilin-1 (NRP-1), has been reported to amplify the viral infection. Interestingly, NRP-1 is expressed in nonparenchymal liver cells and is related to and upregulated in a wide variety of liver-related pathologies. It has been observed that SARS-CoV-2 infection promotes liver injury through several pathways that may be influenced by the previous pathological status of the patient and liver expression of NRP-1. Moreover, coronavirus disease 2019 causes an inflammatory cascade called cytokine storm in patients with severe disease. This cytokine storm may influence liver sinusoidal-cell phenotype, facilitating viral invasion. In this review, the shreds of evidence linking NRP-1 with liver pathologies such as hepatocellular carcinoma, liver fibrosis, nonalcoholic fatty liver disease and inflammatory disorders are discussed in the context of SARS-CoV-2 infection. In addition, the involvement of the infection-related cytokine storm in NRP-1 overexpression and the subsequent increased risk of SARS-CoV-2 infection are also analyzed. This review aims to shed some light on the involvement of liver NRP-1 during SARS-CoV-2 infection and emphasizes the possible involvement this receptor with the observed liver damage.

Use of NanoBiT and NanoBRET to monitor fluorescent VEGF-A binding kinetics to VEGFR2/NRP1 heteromeric complexes in living cells

BACKGROUND AND PURPOSE

VEGF-A is a key mediator of angiogenesis, primarily signalling via VEGF receptor 2 (VEGFR2). Endothelial cells also express the co-receptor neuropilin-1 (NRP1) that potentiates VEGF-A/VEGFR2 signalling. VEGFR2 and NRP1 had distinct real-time ligand binding kinetics when monitored using BRET. We previously characterised fluorescent VEGF-A isoforms tagged at a single site with tetramethylrhodamine (TMR). Here, we explored differences between VEGF-A isoforms in living cells that co-expressed both receptors.

EXPERIMENTAL APPROACH

Receptor localisation was monitored in HEK293T cells expressing both VEGFR2 and NRP1 using membrane-impermeant HaloTag and SnapTag technologies. To isolate ligand binding pharmacology at a defined VEGFR2/NRP1 complex, we developed an assay using NanoBiT complementation technology whereby heteromerisation is required for luminescence emissions. Binding affinities and kinetics of VEGFR2-selective VEGF165 b-TMR and non-selective VEGF165 a-TMR were monitored using BRET from this defined complex.

KEY RESULTS

Cell surface VEGFR2 and NRP1 were co-localised and formed a constitutive heteromeric complex. Despite being selective for VEGFR2, VEGF165 b-TMR had a distinct kinetic ligand binding profile at the complex that largely remained elevated in cells over 90 min. VEGF165 a-TMR bound to the VEGFR2/NRP1 complex with kinetics comparable to those of VEGFR2 alone. Using a binding-dead mutant of NRP1 did not affect the binding kinetics or affinity of VEGF165 a-TMR.

CONCLUSION AND IMPLICATIONS

This NanoBiT approach enabled real-time ligand binding to be quantified in living cells at 37°C from a specified complex between a receptor TK and its co-receptor for the first time.

Novel Compounds Targeting Neuropilin Receptor 1 with Potential To Interfere with SARS-CoV-2 Virus Entry

Neuropilin-1 (NRP-1) is a multifunctional transmembrane receptor for ligands that affect developmental axonal growth and angiogenesis. In addition to a role in cancer, NRP-1 is a reported entry point for several viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of coronavirus disease 2019 (COVID-19). The furin cleavage product of SARS-CoV-2 Spike protein takes advantage of the vascular endothelial growth factor A (VEGF-A) binding site on NRP-1 which accommodates a polybasic stretch ending in a C-terminal arginine. This site has long been a focus of drug discovery efforts for cancer therapeutics. We recently showed that interruption of the VEGF-A/NRP-1 signaling pathway ameliorates neuropathic pain and hypothesize that interference of this pathway by SARS-CoV-2 Spike protein interferes with pain signaling. Here, we report confirmed hits from a small molecule and natural product screen of nearly 0.5 million compounds targeting the VEGF-A binding site on NRP-1. We identified nine chemical series with lead- or drug-like physicochemical properties. Using ELISA, we demonstrate that six compounds disrupt VEGF-A-NRP-1 binding more effectively than EG00229, a known NRP-1 inhibitor. Secondary validation in cells revealed that all tested compounds inhibited VEGF-A triggered VEGFR2 phosphorylation. Further, two compounds displayed robust inhibition of a recombinant vesicular stomatitis virus protein that utilizes the SARS-CoV-2 Spike for entry and fusion. These compounds represent a first step in a renewed effort to develop small molecule inhibitors of the VEGF-A/NRP-1 signaling for the treatment of neuropathic pain and cancer with the added potential of inhibiting SARS-CoV-2 virus entry.

Soluble Neuropilin-1 Response to Hypoglycemia in Type 2 Diabetes: Increased Risk or Protection in SARS-CoV-2 Infection?

INTRODUCTION

Neuropilin-1(NRP1) is a cofactor that enhances SARS-CoV-2 coronavirus cell infectivity when co-expressed with angiotensin-converting enzyme 2(ACE2). The Renin-Angiotensin System (RAS) is activated in type 2 diabetes (T2D); therefore, the aim of this study was to determine if hypoglycaemia-induced stress in T2D would potentiate serum NRP1(sNRP1) levels, reflecting an increased risk for SARS-CoV-2 infection.

METHODS

A case-control study of aged-matched T2D (n = 23) and control (n = 23) subjects who underwent a hyperinsulinemic clamp over 1-hour to hypoglycemia(<40mg/dl) with subsequent timecourse of 4-hours and 24-hours. Slow Off-rate Modified Aptamer (SOMA)-scan plasma protein measurement determined RAS-related proteins: renin (REN), angiotensinogen (AGT), ACE2, soluble NRP1(sNRP1), NRP1 ligands (Vascular endothelial growth factor, VEGF and Class 3 Semaphorins, SEM3A) and NRP1 proteolytic enzyme (A Disintegrin and Metalloproteinase 9, ADAM9).

RESULTS

Baseline RAS overactivity was present with REN elevated and AGT decreased in T2D (p<0.05); ACE2 was unchanged. Baseline sNRP1, VEGF and ADAM9 did not differ between T2D and controls and remained unchanged in response to hypoglycaemia. However, 4-hours post-hypoglycemia, sNRP1, VEGF and ADAM9 were elevated in T2D(p<0.05). SEMA3A was not different at baseline; at hypoglycemia, SEMA3A decreased in controls only. Post-hypoglycemia, SEMA3A levels were higher in T2D versus controls. sNRP1 did not correlate with ACE2, REN or AGT. T2D subjects stratified according to ACE inhibitor (ACEi) therapies showed no difference in sNRP1 levels at either glucose normalization or hypoglycaemia.

CONCLUSION

Hypoglycemia potentiated both plasma sNRP1 level elevation and its ligands VEGF and SEMA3A, likely through an ADAM9-mediated mechanism that was not associated with RAS overactivity or ACEi therapy; however, whether this is protective or promotes increased risk for SARS-CoV-2 infection in T2D is unclear.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov, identifier NCT03102801.

Urea-Peptide Hybrids as VEGF-A165/NRP-1 Complex Inhibitors with Improved Receptor Affinity and Biological Properties

Neuropilin-1 (NRP-1), the major co-receptor of vascular endothelial growth factor receptor-2 (VEGFR-2), may also independently act with VEGF-A₁₆₅ to stimulate tumour growth and metastasis. Therefore, there is great interest in compounds that can block VEGF-A165/NRP-1 interaction. Peptidomimetic type inhibitors represent a promising strategy in the treatment of NRP-1-related disorders. Here, we present the synthesis, affinity, enzymatic stability, molecular modeling and in vitro binding evaluation of the branched urea–peptide hybrids, based on our previously reported Lys(hArg)-Dab-Oic-Arg active sequence, where the Lys(hArg) branching has been modified by introducing urea units to replace the peptide bond at various positions. One of the resulting hybrids increased the affinity of the compound for NRP-1 more than 10-fold, while simultaneously improving resistance for proteolytic stability in serum. In addition, ligand binding to NRP-1 induced rapid protein stock exocytotic trafficking to the plasma membrane in breast cancer cells. Examined properties characterize this compound as a good candidate for further development of VEGF₁₆₅/NRP-1 inhibitors.

A Dual Receptor Targeting- and BBB Penetrating- Peptide Functionalized Polyethyleneimine Nanocomplex for Secretory Endostatin Gene Delivery to Malignant Glioma

PURPOSE

Vascular endothelial growth factor receptor 2 (VEGFR-2) and neuropilin-1 (NRP-1) are two prominent synergistic receptors overexpressed on new blood vessels in glioma and may be promising targets for antiglioma therapy. The aim of this study was to design a dual receptor targeting and blood-brain barrier (BBB) penetrating peptide-modified polyethyleneimine (PEI) nanocomplex that can efficiently deliver the angiogenesis-inhibiting secretory endostatin gene (pVAXI-En) to treat glioma.

MATERIALS AND METHODS

We first constructed the tandem peptide TAT-AT7 by conjugating AT7 to TAT and evaluated its binding affinity to VEGFR-2 and NRP-1, vasculature-targeting ability and BBB crossing capacity. Then, TAT-AT7-modified PEI polymer (PPTA) was synthesized, and a pVAXI-En-loaded PPTA nanocomplex (PPTA/pVAXI-En) was prepared. The physicochemical properties, cytotoxicity, transfection efficiency, capacities to cross the BBB and BTB (blood-tumor barrier) and glioma-targeting properties of PPTA/pVAXI-En were investigated. Moreover, the in vivo anti-angiogenic behaviors and anti-glioma effects of PPTA/pVAXI-En were evaluated in nude mice.

RESULTS

The binding affinity of TAT-AT7 to VEGFR-2 and NRP-1 was approximately 3 to 10 times greater than that of AT7 or TAT. The cellular uptake of TAT-AT7 in endothelial cells was 5-fold and 119-fold greater than that of TAT and AT7 alone, respectively. TAT-AT7 also displayed remarkable efficiency in penetrating the BBB and glioma tissue in vivo. PPTA/pVAXI-En exhibited lower cytotoxicity, stronger BBB and BTB traversing abilities, higher selective glioma targeting and better gene transfection efficiency than PEI/pVAXI-En. More importantly, PPTA/pVAXI-En significantly suppressed the tube formation and migration of endothelial cells, inhibited glioma growth, and reduced the microvasculature in orthotopic U87 glioma-bearing nude mice.

CONCLUSION

Our study demonstrates that PPTA/pVAXI-En can be exploited as an efficient dual-targeting nanocomplex to cross the BBB and BTB, and hence it represents a feasible and promising nonviral gene delivery system for effective glioma therapy.

In silico identification and validation of inhibitors of the interaction between neuropilin receptor 1 and SARS-CoV-2 Spike protein

Neuropilin-1 (NRP-1) is a multifunctional transmembrane receptor for ligands that affect developmental axonal growth and angiogenesis. In addition to a role in cancer, NRP-1 is a reported entry point for several viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of coronavirus disease 2019 (COVID-19). The furin cleavage product of SARS-CoV-2 Spike protein takes advantage of the vascular endothelial growth factor A (VEGF-A) binding site on NRP-1 which accommodates a polybasic stretch ending in a C-terminal arginine. This site has long been a focus of drug discovery efforts for cancer therapeutics. We recently showed that interruption of the VEGF-A/NRP-1 signaling pathway ameliorates neuropathic pain and hypothesize that interference of this pathway by SARS-CoV-2 spike protein interferes with pain signaling. Here, we report hits from a small molecule and natural product screen of nearly 0.5 million compounds targeting the VEGF-A binding site on NRP-1. We identified nine chemical series with lead- or drug-like physico-chemical properties. Using an ELISA, we demonstrate that six compounds disrupt VEGF-A-NRP-1 binding more effectively than EG00229, a known NRP-1 inhibitor. Secondary validation in cells revealed that almost all tested compounds inhibited VEGF-A triggered VEGFR2 phosphorylation. Two compounds displayed robust inhibition of a recombinant vesicular stomatitis virus protein that utilizes the SARS-CoV-2 Spike for entry and fusion. These compounds represent a first step in a renewed effort to develop small molecule inhibitors of the VEGF-A/NRP-1 signaling for the treatment of neuropathic pain and cancer with the added potential of inhibiting SARS-CoV-2 virus entry.

miR-331-3p Suppresses Cell Proliferation in TNBC Cells by Downregulating NRP2

PURPOSE

Triple-negative breast cancer is characterized by fast progression with high possible for metastasis and poor survival. Dysfunction of microRNAs plays an important role in the initiation and progression of cancer. Our previous microRNA-seq data indicated the downregulation of miR-331-3p in triple-negative breast cancer tissues compared with that of the noncancer tissues. However, the function of miR-331-3p in triple-negative breast cancer remains largely unknown. Herein, the involvement of miR-331-3p in triple-negative breast cancer was investigated and the therapeutic potential of miR-331-3p was also explored.

METHODS

Real-time quantitative polymerase chain reaction was performed to detect the expression of miR-331-3p in triple-negative breast cancer tissues and cell lines. The cell proliferation was determined by the cell counting kit-8 assay. Apoptosis of triple-negative breast cancer cells was examined by annexin V/propidium iodide staining. miRDB database was used to predict the potential targets of miR-331-3p. Western blot was performed to examine the expression of the target protein.

RESULTS

miR-331-3p was significantly downregulated in triple-negative breast cancer tissues and cell line. Lower miR-331-3p expression was significantly correlated with the tumor size, TNM stage, and lymph node metastasis of patients with triple-negative breast cancer. Functional experiments showed that the overexpression of miR-331-3p inhibited the proliferation and increased apoptosis of triple-negative breast cancer cells. Neuropilin-2 was identified as a target of miR-331-3p, which harbored binding site of miR-331-3p in its 3'-untranslated region. Overexpression of miR-331-3p decreased the messenger RNA and protein levels of neuropilin-2 in triple-negative breast cancer cells. Restoration of neuropilin-2 partially reversed the inhibitory effects of miR-331-3p on the proliferation of triple-negative breast cancer cells.

CONCLUSIONS

Our results demonstrated the novel function of miR-331-3p/neuropilin-2 signaling in regulating the malignant behaviors of triple-negative breast cancer cells, which suggested miR-331-3p as a potential target for the treatment of triple-negative breast cancer.

Human cardiac fibroblasts expressing VCAM1 improve heart function in postinfarct heart failure rat models by stimulating lymphangiogenesis

Cardiovascular diseases are a leading cause of death worldwide. After an ischemic injury, the myocardium undergoes severe necrosis and apoptosis, leading to a dramatic degradation of function. Numerous studies have reported that cardiac fibroblasts (CFs) play a critical role in heart function even after injury. However, CFs present heterogeneous characteristics according to their development stage (i.e., fetal or adult), and the molecular mechanisms by which they maintain heart function are not fully understood. The aim of this study is to explore the hypothesis that a specific population of CFs can repair the injured myocardium in heart failure following ischemic infarction, and lead to a significant recovery of cardiac function. Flow cytometry analysis of CFs defined two subpopulations according to their relative expression of vascular cell adhesion molecule 1 (VCAM1). Whole-transcriptome analysis described distinct profiles for these groups, with a correlation between VCAM1 expression and lymphangiogenesis-related genes up-regulation. Vascular formation assays showed a significant stimulation of lymphatic cells network complexity by VCFs. Injection of human VCAM1-expressing CFs (VCFs) in postinfarct heart failure rat models (ligation of the left anterior descending artery) led to a significant restoration of the left ventricle contraction. Over the course of the experiment, left ventricular ejection fraction and fractional shortening increased by 16.65% ± 5.64% and 10.43% ± 6.02%, respectively, in VCF-treated rats. Histological examinations revealed that VCFs efficiently mobilized the lymphatic endothelial cells into the infarcted area. In conclusion, human CFs present heterogeneous expression of VCAM1 and lymphangiogenesis-promoting factors. VCFs restore the mechanical properties of ventricular walls by mobilizing lymphatic endothelial cells into the infarct when injected into a rat heart failure model. These results suggest a role of this specific population of CFs in the homeostasis of the lymphatic system in cardiac regeneration, providing new information for the study and therapy of cardiac diseases.

Neuropilin: Handyman and Power Broker in the Tumor Microenvironment

Neuropilin-1 and neuropilin-2 form a small family of transmembrane receptors, which, due to the lack of a cytosolic protein kinase domain, act primarily as co-receptors for various ligands. Performing at the molecular level both the executive and organizing functions of a handyman as well as of a power broker, they are instrumental in controlling the signaling of various receptor tyrosine kinases, integrins, and other molecules involved in the regulation of physiological and pathological angiogenic processes. In this setting, the various neuropilin ligands and interaction partners on various cells of the tumor microenvironment, such as cancer cells, endothelial cells, cancer-associated fibroblasts, and immune cells, are surveyed. The suitability of various neuropilin-targeting substances and the intervention in neuropilin-mediated interactions is considered as a possible building block of tumor therapy.

Dual Action of Sulfated Hyaluronan on Angiogenic Processes in Relation to Vascular Endothelial Growth Factor-A

Pathological healing characterized by abnormal angiogenesis presents a serious burden to patients’ quality of life requiring innovative treatment strategies. Glycosaminoglycans (GAG) are important regulators of angiogenic processes. This experimental and computational study revealed how sulfated GAG derivatives (sGAG) influence the interplay of vascular endothelial growth factor (VEGF)₁₆₅ and its heparin-binding domain (HBD) with the signaling receptor VEGFR-2 up to atomic detail. There was profound evidence for a HBD-GAG-HBD stacking configuration. Here, the sGAG act as a “molecular glue” leading to recognition modes in which sGAG interact with two VEGF₁₆₅-HBDs. A 3D angiogenesis model demonstrated the dual regulatory role of high-sulfated derivatives on the biological activity of endothelial cells. While GAG alone promote sprouting, they downregulate VEGF₁₆₅-mediated signaling and, thereby, elicit VEGF₁₆₅-independent and -dependent effects. These findings provide novel insights into the modulatory potential of sGAG derivatives on angiogenic processes and point towards their prospective application in treating abnormal angiogenesis.

The functions and applications of A7R in anti-angiogenic therapy, imaging and drug delivery systems

Vascular endothelial growth factor receptor 2 (VEGFR-2) and neuropilin-1 (NRP-1) are two prominent antiangiogenic targets. They are highly expressed on vascular endothelial cells and some tumor cells. Therefore, targeting VEGFR-2 and NRP-1 may be a potential antiangiogenic and antitumor strategy. A7R, a peptide with sequence of Ala-Thr-Trp-Leu-Pro-Pro-Arg that was found by phage display of peptide libraries, can preferentially target VEGFR-2 and NRP-1 and destroy the binding between vascular endothelial growth factor 165 (VEGF165) and VEGFR-2 or NRP-1. This peptide is a new potent inhibitor of tumor angiogenesis and a targeting ligand for cancer therapy. This review describes the discovery, function and mechanism of the action of A7R, and further introduces the applications of A7R in antitumor angiogenic treatments, tumor angiogenesis imaging and targeted drug delivery systems. In this review, strategies to deliver different drugs by A7R-modified liposomes and nanoparticles are highlighted. A7R, a new dual targeting ligand of VEGFR-2 and NRP-1, is expected to have efficient therapeutic or targeting roles in tumor drug delivery.

Characterization of a sandwich ELISA for quantification of total human soluble neuropilin-1

Background

Neuropilin‐1 (NRP1) is a highly interactive molecule that exists as transmembrane and soluble isoforms. Measurement of circulating levels of soluble NRP1 (sNRP1) in human serum and plasma has proven to be difficult due to present matrix interferences and due to the lack of a reliable technique.

Methods

We developed a highly specific and sensitive sandwich ELISA assay for total sNRP1 quantification in peripheral blood, and we validated the test according to ICH guidelines. The linear epitopes of the employed polyclonal and monoclonal anti‐human NRP1 antibodies were mapped with microarray technology. We included a sample pre‐treatment step with guanidine hydrochloride (GuHCl) to release sNRP1 from existing interferants.

Results

The ELISA assay which is calibrated with sNRP1 isoform 2 and covers a calibration range from 0.375 to 12 nmol/L detects sNRP1 in human serum and plasma (heparin, EDTA, and citrate). Multiple linear epitopes recognized by the polyclonal coating antibody are distributed over the whole sNRP1 sequence. The monoclonal detection antibody binds to a linear epitope which is in the N‐terminal region of the a1 domain of human sNRP1. Assay parameters like precision (intra‐assay: 6%), dilution linearity (95%‐115%), specificity (98%), and spike recovery (81%‐109%) meet the international standards of acceptance.

Conclusion

Our novel sandwich ELISA provides a reliable tool for the quantitative determination of total human sNRP1. The assay detects free and previous ligand‐bound total NRP1.

Triazolopeptides Inhibiting the Interaction between Neuropilin-1 and Vascular Endothelial Growth Factor-165

Inhibiting the interaction of neuropilin-1 (NRP-1) with vascular endothelial growth factor (VEGF) has become an interesting mechanism for potential anticancer therapies. In our previous works, we have obtained several submicromolar inhibitors of this interaction, including branched pentapeptides of general structure Lys(Har)-Xxx-Xxx-Arg. With the intent to improve the proteolytic stability of our inhibitors, we turned our attention to 1,4-disubstituted 1,2,3-triazoles as peptide bond isosteres. In the present contribution, we report the synthesis of 23 novel triazolopeptides along with their inhibitory activity. The compounds were synthesized using typical peptide chemistry methods, but with a conversion of amine into azide completely on solid support. The inhibitory activity of the synthesized derivatives spans from 9.2% to 58.1% at 10 μM concentration (the best compound Lys(Har)-GlyΨ[Trl]GlyΨ[Trl]Arg, 3, IC₅₀ = 8.39 μM). Synthesized peptidotriazoles were tested for stability in human plasma and showed remarkable resistance toward proteolysis, with half-life times far exceeding 48 h. In vitro cell survival test resulted in no significant impact on bone marrow derived murine cells 32D viability. By means of molecular dynamics, we were able to propose a binding mode for compound 3 and discuss the observed structure–activity relationships.

NRP-1 interacts with GIPC1 and SYX to activate p38 MAPK signaling and cancer stem cell survival

Epidermal cancer stem cells (ECS cells) comprise a limited population of cells that form aggressive, rapidly growing, and highly vascularized tumors. VEGF-A/NRP-1 signaling is a key driver of the ECS cell phenotype and aggressive tumor formation. However, relatively less is known regarding the downstream events following VEGF-A/NRP-1 interaction. In the present study, we show that VEGF-A/NRP-1, GIPC1, and Syx interact to increase RhoA-dependent p38 MAPK activity to enhance ECS cell spheroid formation, invasion, migration, and angiogenic potential. Inhibition or knockdown of NRP-1, GIPC1 or Syx attenuates RhoA and p38 activity to reduce the ECS cell phenotype, and NRP-1 knockout, or pharmacologic inhibition of VEGF-A/NRP-1 interaction or RhoA activity, reduces p38 MAPK activity and tumor growth. Moreover, expression of wild-type or constitutively-active RhoA, or p38, in NRP1-knockout cells, restores p38 activity and the ECS cell phenotype. These findings suggest that NRP-1 forms a complex with GIPC1 and Syx to activate RhoA/ROCK-dependent p38 activity to enhance the ECS cell phenotype and tumor formation.

Phytochemicals Targeting VEGF and VEGF-Related Multifactors as Anticancer Therapy

The role of vascular endothelial growth factor (VEGF) in cancer cells is not limited to angiogenesis; there are also multiple factors, such as neuropilins (non-tyrosine kinases receptors), tyrosine kinases receptors, immunodeficiencies, and integrins, that interact with VEGF signaling and cause cancer initiation. By combating these factors, tumor progression can be inhibited or limited. Natural products are sources of several bioactive phytochemicals that can interact with VEGF-promoting factors and inhibit them through various signaling pathways, thereby inhibiting cancer growth. This review provides a deeper understanding of the relation and interaction of VEGF with cancer-promoting factors and phytochemicals in order to develop multi-targeted cancer prevention and treatment.

Neuropilins in the Context of Tumor Vasculature

Neuropilin-1 and Neuropilin-2 form a small family of plasma membrane spanning receptors originally identified by the binding of semaphorin and vascular endothelial growth factor. Having no cytosolic protein kinase domain, they function predominantly as co-receptors of other receptors for various ligands. As such, they critically modulate the signaling of various receptor tyrosine kinases, integrins, and other molecules involved in the regulation of physiological and pathological angiogenic processes. This review highlights the diverse neuropilin ligands and interacting partners on endothelial cells, which are relevant in the context of the tumor vasculature and the tumor microenvironment. In addition to tumor cells, the latter contains cancer-associated fibroblasts, immune cells, and endothelial cells. Based on the prevalent neuropilin-mediated interactions, the suitability of various neuropilin-targeted substances for influencing tumor angiogenesis as a possible building block of a tumor therapy is discussed.

Neuroimmune Semaphorin 4A in Cancer Angiogenesis and Inflammation: A Promoter or a Suppressor?

Neuroimmune semaphorin 4A (Sema4A), a member of semaphorin family of transmembrane and secreted proteins, is an important regulator of neuronal and immune functions. In the nervous system, Sema4A primarily regulates the functional activity of neurons serving as an axon guidance molecule. In the immune system, Sema4A regulates immune cell activation and function, instructing a fine tuning of the immune response. Recent studies have shown a dysregulation of Sema4A expression in several types of cancer such as hepatocellular carcinoma, colorectal, and breast cancers. Cancers have been associated with abnormal angiogenesis. The function of Sema4A in angiogenesis and cancer is not defined. Recent studies have demonstrated Sema4A expression and function in endothelial cells. However, the results of these studies are controversial as they report either pro- or anti-angiogenic Sema4A effects depending on the experimental settings. In this mini-review, we discuss these findings as well as our data on Sema4A regulation of inflammation and angiogenesis, which both are important pathologic processes underlining tumorigenesis and tumor metastasis. Understanding the role of Sema4A in those processes may guide the development of improved therapeutic treatments for cancer.

The role of placental growth factor (PlGF) and its receptor system in retinal vascular diseases

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. Upon binding to VEGF- and neuropilin-receptor sub-types, PlGF modulates a range of neural, glial and vascular cell responses that are distinct from VEGF-A. As PlGF expression is selectively associated with pathological angiogenesis and inflammation, its blockade does not affect the healthy vasculature. PlGF actions have been extensively described in tumor biology but more recently there has been accumulating preclinical evidence that indicates that this growth factor could have an important role in retinal diseases. High levels of PlGF have been found in aqueous humor, vitreous and/or retina of patients exhibiting retinopathies, especially those with diabetic retinopathy (DR) and neovascular age-related macular degeneration (nvAMD). Expression of this growth factor seems to correlate closely with many of the key pathogenic features of early and late retinopathy in preclinical models. For example, studies using genetic modification and/or pharmacological treatment to block PlGF in the laser-induced choroidal neovascularization (CNV) model, oxygen-induced retinopathy model, as well as various murine diabetic models, have shown that PlGF deletion or inhibition can reduce neovascularization, retinal leakage, inflammation and gliosis, without affecting vascular development or inducing neuronal degeneration. Moreover, an inhibitory effect of PlGF blockade on retinal scarring in the mouse CNV model has also been recently demonstrated and was found to be unique for PlGF inhibition, as compared to various VEGF inhibition strategies. Together, these preclinical results suggest that anti-PlGF therapy might have advantages over anti-VEGF treatment, and that it may have clinical applications as a standalone treatment or in combination with anti-VEGF. Additional clinical studies are clearly needed to further elucidate the role of PlGF and its potential as a therapeutic target in ocular diseases.

NRP-1 interacts with GIPC1 and α6/β4-integrins to increase YAP1/∆Np63α-dependent epidermal cancer stem cell survival

We have identified an epidermal cancer stem (ECS) cell population that drives formation of rapidly growing and highly invasive and vascularized tumors. VEGF-A and neuropilin-1 (NRP-1) are highly expressed in ECS cell tumors and VEGF-A/NRP-1 interaction is required for ECS cell survival and tumor vascularization. We now identify a novel signaling cascade that is triggered by VEGF-A/NRP-1. We show that NRP-1 forms a complex with GIPC1 and α6/β4-integrin to activate FAK/Src signaling, which leads to stabilization of a YAP1/∆Np63α to enhance ECS cell survival, invasion, and angiogenesis. Loss of NRP-1, GIPC1, α6/β4-integrins, YAP1, or ∆Np63α reduces these responses. Moreover, restoration of constituently active YAP1 or ∆Np63α in NRP-1 null cells restores the ECS cell phenotype. Tumor xenograft experiments show that NRP-1 knockout ECS cells form small tumors characterized by reduced vascularization as compared to wild-type cells. The NRP-1 knockout tumors display signaling changes consistent with a role for the proposed signaling cascade. These studies suggest that VEGF-A interacts with NRP-1 and GIPC1 to regulate α6/β4-integrin, FAK, Src, PI3K/PDK1, LATS1 signaling to increase YAP1/∆Np63α accumulation to drive ECS cell survival, angiogenesis, and tumor formation.

Real-Time Ligand Binding of Fluorescent VEGF-A Isoforms that Discriminate between VEGFR2 and NRP1 in Living Cells

Fluorescent VEGF-A isoforms have been evaluated for their ability to discriminate between VEGFR2 and NRP1 in real-time ligand binding studies in live cells using BRET. To enable this, we synthesized single-site (N-terminal cysteine) labeled versions of VEGF₁₆₅a, VEGF₁₆₅b, and VEGF₁₂₁a. These were used in combination with N-terminal NanoLuc-tagged VEGFR2 or NRP1 to evaluate the selectivity of VEGF isoforms for these two membrane proteins. All fluorescent VEGF-A isoforms displayed high affinity for VEGFR2. Only VEGF₁₆₅a-TMR bound to NanoLuc-NRP1 with a similar high affinity (4.4 nM). Competition NRP1 binding experiments yielded a rank order of potency of VEGF₁₆₅a > VEGF₁₈₉a > VEGF₁₄₅a. VEGF₁₆₅b, VEGF-Ax, VEGF₁₂₁a, and VEGF₁₁₁a were unable to bind to NRP1. There were marked differences in the kinetic binding profiles of VEGF₁₆₅a-TMR for NRP1 and VEGFR2. These data emphasize the importance of the kinetic aspects of ligand binding to VEGFR2 and its co-receptors in the dynamics of VEGF signaling.

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VEGF₁₆₅a, VEGF₁₂₁a, and VEGF₁₆₅b were single-site labeled with tetramethylrhodamine

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NanoBRET quantified that VEGF-A isoforms have similar binding properties at VEGFR2

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NRP1 expressed in live cells does not bind VEGF₁₆₅b, VEGF₁₂₁a, VEGF-Ax, or VEGF₁₁₁a

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VEGFR2 and NRP1 have markedly distinct kinetic profiles binding VEGF₁₆₅a-TMR

Molecular Pharmacology of VEGF-A Isoforms: Binding and Signalling at VEGFR2

Vascular endothelial growth factor-A (VEGF-A) is a key mediator of angiogenesis, signalling via the class IV tyrosine kinase receptor family of VEGF Receptors (VEGFRs). Although VEGF-A ligands bind to both VEGFR1 and VEGFR2, they primarily signal via VEGFR2 leading to endothelial cell proliferation, survival, migration and vascular permeability. Distinct VEGF-A isoforms result from alternative splicing of the Vegfa gene at exon 8, resulting in VEGFxxxa or VEGFxxxb isoforms. Alternative splicing events at exons 5⁻7, in addition to recently identified posttranslational read-through events, produce VEGF-A isoforms that differ in their bioavailability and interaction with the co-receptor Neuropilin-1. This review explores the molecular pharmacology of VEGF-A isoforms at VEGFR2 in respect to ligand binding and downstream signalling. To understand how VEGF-A isoforms have distinct signalling despite similar affinities for VEGFR2, this review re-evaluates the typical classification of these isoforms relative to the prototypical, “pro-angiogenic” VEGF165a. We also examine the molecular mechanisms underpinning the regulation of VEGF-A isoform signalling and the importance of interactions with other membrane and extracellular matrix proteins. As approved therapeutics targeting the VEGF-A/VEGFR signalling axis largely lack long-term efficacy, understanding these isoform-specific mechanisms could aid future drug discovery efforts targeting VEGF receptor pharmacology.

Vascular Endothelial Growth Factor B and Its Signaling

In diabetes, compromised glucose utilization leads the heart to use FA almost exclusively for ATP generation. Chronically, this adaptation unfortunately leads to the conversion of FA to potentially toxic FA metabolites. Paired with increased formation of reactive oxygen species related to excessive mitochondrial oxidation of FA, can provoke cardiac cell death. To protect against this cell demise, intrinsic mechanisms must be available to the heart. Vascular endothelial growth factor B (VEGFB) may be one growth factor that plays an important role in protecting against heart failure. As a member of the VEGF family, initial studies with VEGFB focused on its role in angiogenesis. Surprisingly, VEGFB does not appear to play a direct role in angiogenesis under normal conditions or even when overexpressed, but has been implicated in influencing vascular growth indirectly by affecting VEGFA action. Intriguingly, VEGFB has also been shown to alter gene expression of proteins involved in cardiac metabolism and promote cell survival. Conversely, multiple models of heart failure, including diabetic cardiomyopathy, have indicated a significant drop in VEGFB. In this review, we will discuss the biology of VEGFB, and its relationship to diabetic cardiomyopathy.

Semaphorin 3C and Its Receptors in Cancer and Cancer Stem-Like Cells

Neurodevelopmental programs are frequently dysregulated in cancer. Semaphorins are a large family of guidance cues that direct neuronal network formation and are also implicated in cancer. Semaphorins have two kinds of receptors, neuropilins and plexins. Besides their role in development, semaphorin signaling may promote or suppress tumors depending on their context. Sema3C is a secreted semaphorin that plays an important role in the maintenance of cancer stem-like cells, promotes migration and invasion, and may facilitate angiogenesis. Therapeutic strategies that inhibit Sema3C signaling may improve cancer control. This review will summarize the current research on the Sema3C pathway and its potential as a therapeutic target.

Role of the Nervous System in Tumor Angiogenesis

The development of cancer involves an intricate process, wherein many identified and unidentified factors play a role. Tumor angiogenesis, growth of new blood vessels, is one of the major prerequisites for tumor growth as tumor cells rely on adequate oxygen and nutrient supply as well as the removal of waste products. Growth factors including VEGF orchestrate the development of angiogenesis. In addition, nervous system via the release of neurotransmitters contributes to tumor angiogenesis. The nervous system governs functional activities of many organs, and, as tumors are not independent organs within an organism, this system is integrally involved in tumor growth and progression via regulating tumor angiogenesis. Various neurotransmitters have been reported to play an important role in tumor angiogenesis.