The interaction of Neuropilin-1 and Neuropilin-2 with tyrosine-kinase receptors for VEGF

Semaphorin Receptors Antagonize Wnt Signaling Through Beta-Catenin Degradation

Precise control of morphogen signaling levels is essential for proper development. An outstanding question is: what mechanisms ensure proper morphogen activity and correct cellular responses? Previous work has identified Semaphorin (SEMA) receptors, Neuropilins (NRPs) and Plexins (PLXNs), as positive regulators of the Hedgehog (HH) signaling pathway. Here, we provide evidence that NRPs and PLXNs antagonize Wnt signaling in both fibroblasts and epithelial cells. Further, Nrp1/2 deletion in fibroblasts results in elevated baseline Wnt pathway activity and increased maximal responses to Wnt stimulation. Notably, and in contrast to HH signaling, SEMA receptor-mediated Wnt antagonism is independent of primary cilia. Mechanistically, PLXNs and NRPs act downstream of Dishevelled (DVL) to destabilize β-catenin (CTNNB1) in a proteosome-dependent manner. Further, NRPs, but not PLXNs, act in a GSK3β/CK1-dependent fashion to antagonize Wnt signaling, suggesting distinct repressive mechanisms for these SEMA receptors. Overall, this study identifies SEMA receptors as novel Wnt pathway antagonists that may also play larger roles integrating signals from multiple inputs.

The VEGFs/VEGFRs system in Alzheimer's and Parkinson's diseases: Pathophysiological roles and therapeutic implications

The vascular endothelial growth factors (VEGFs) and their cognate receptors (VEGFRs), besides their well-known involvement in physiological angiogenesis/lymphangiogenesis and in diseases associated to pathological vessel formation, play multifaceted functions in the central nervous system (CNS). In addition to shaping brain development, by controlling cerebral vasculogenesis and regulating neurogenesis as well as astrocyte differentiation, the VEGFs/VEGFRs axis exerts essential functions in the adult brain both in physiological and pathological contexts. In this article, after describing the physiological VEGFs/VEGFRs functions in the CNS, we focus on the VEGFs/VEGFRs involvement in neurodegenerative diseases by reviewing the current literature on the rather complex VEGFs/VEGFRs contribution to the pathogenic mechanisms of Alzheimer's (AD) and Parkinson's (PD) diseases. Thereafter, based on the outcome of VEGFs/VEGFRs targeting in animal models of AD and PD, we discuss the factual relevance of pharmacological VEGFs/VEGFRs modulation as a novel and potential disease-modifying approach for these neurodegenerative pathologies. Specific VEGFRs targeting, aimed at selective VEGFR-1 inhibition, while preserving VEGFR-2 signal transduction, appears as a promising strategy to hit the molecular mechanisms underlying AD pathology. Moreover, therapeutic VEGFs-based approaches can be proposed for PD treatment, with the aim of fine-tuning their brain levels to amplify neurotrophic/neuroprotective effects while limiting an excessive impact on vascular permeability.

Pleiotrophin and the Expression of Its Receptors during Development of the Human Cerebellar Cortex

During embryonic and fetal development, the cerebellum undergoes several histological changes that require a specific microenvironment. Pleiotrophin (PTN) has been related to cerebral and cerebellar cortex ontogenesis in different species. PTN signaling includes PTPRZ1, ALK, and NRP-1 receptors, which are implicated in cell differentiation, migration, and proliferation. However, its involvement in human cerebellar development has not been described so far. Therefore, we investigated whether PTN and its receptors were expressed in the human cerebellar cortex during fetal and early neonatal development. The expression profile of PTN and its receptors was analyzed using an immunohistochemical method. PTN, PTPRZ1, and NRP-1 were expressed from week 17 to the postnatal stage, with variable expression among granule cell precursors, glial cells, and Purkinje cells. ALK was only expressed during week 31. These results suggest that, in the fetal and neonatal human cerebellum, PTN is involved in cell communication through granule cell precursors, Bergmann glia, and Purkinje cells via PTPRZ1, NRP-1, and ALK signaling. This communication could be involved in cell proliferation and cellular migration. Overall, the present study represents the first characterization of PTN, PTPRZ1, ALK, and NRP-1 expression in human tissues, suggesting their involvement in cerebellar cortex development.

Association between the VEGFR-2 -604T/C polymorphism (rs2071559) and type 2 diabetic retinopathy

This retrospective case-control study examined the association between the rs2071559 (-604T/C) single nucleotide polymorphism (SNP) in the vascular endothelial growth factor receptor (VEGFR)-2 gene and the risk of diabetic retinopathy (DR) in Northern Han Chinese. This study included patients diagnosed with diabetes mellitus (DM) in Shijiazhuang between 07/2014 and 07/2016. The healthy controls were unrelated individuals who received routine physical examinations. The diabetic patients were grouped as DM (diabetes but no fundus examination abnormalities), proliferative DR (PDR), and non-proliferative DR (NPDR). Finally, 438 patients were included: 114 controls and 123, 105, and 96 patients in the DM, NPDR, and PDR groups, respectively. In the multivariable analyses and all genetic models, the VEGFR-2 rs2071559 SNP was not associated with DR (among all diabetic patients) or with PDR (among the patients with DR) after adjustment for age, sex, duration of DM, blood glucose, systolic blood pressure, diastolic blood pressure, and body mass index (all P > 0.05). In conclusion, the VEGFR-2- 604T/C rs2071559 SNP is not associated with DR or PDR in the Han Chinese population of Shijiazhuang (China).

CPSF4 promotes tumor-initiating phenotype by enhancing VEGF/NRP2/TAZ signaling in lung cancer

Lung cancer is the leading cause of malignant tumor-related deaths worldwide. The presence of tumor-initiating cells in lung cancer leads to tumor recurrence, metastasis, and resistance to conventional treatment. Cleavage and polyadenylation specificity factor 4 (CPSF4) activation in tumor cells contributes to the poor prognosis of lung cancer. However, the precise biological functions and molecular mechanisms of CPSF4 in the regulation of tumor-initiating cells remain unclear. We demonstrated that CPSF4 promotes tumor-initiating phenotype and confers chemoresistance to paclitaxel both in vitro and in vivo. Mechanistically, we showed that CPSF4 binds to the promoters of vascular endothelial growth factor (VEGF) and neuropilin-2 (NRP2) and activated their transcription. In addition, we showed that CPSF4/VEGF/NRP2-mediated tumor-initiating phenotype and chemoresistance through TAZ induction. Furthermore, analysis of clinical data revealed that lung cancer patients with high CPSF4 expression exhibit high expression levels of VEGF, NRP2, and TAZ and that expression of these proteins are positively correlated with poor prognosis. Importantly, selective inhibition of VEGF, NRP2, or TAZ markedly suppressed CPSF4-mediated tumor-initiating phenotype and chemoresistance. Our findings reveal the mechanism of CPSF4 modulating tumor-initiating phenotype and chemoresistance in lung cancer and indicate that the CPSF4-VEGF-NRP2-TAZ signaling pathway may be a prognosis marker and therapeutic target in lung cancer.

Sars-Cov2 Induced Biochemical Mechanisms in Liver Damage and Intestinal Lesions

Multiple pathogenic mechanisms are found in SARS-CoV2 systemic inflammation. Oxidative stress, altered proteolysis, hypercoagulation, and metabolic disorders are significant in virus-induced lesions. The study aimed to investigate the biochemical mechanism of virus-induced disorders and determine the biochemical features in SARS-CoV2-associated liver damage and intestine lesions. A retrospective case series of ninety-two patients diagnosed with COVID-19 pnemonia. The ACE, α1-proteinase inhibitor, trypsin-like proteinase, and elastase activity were measured. Nitrites level was detected in reaction with Griess reagent. The ELISA kit measured Troponin, C-peptide, leptin, adiponectin, PAR4, and neuropilin level. It was obtained an increase in ACE activity and nitrites ions content in SARS-CoV2 associated patients. The hyperglycemia and an increase in adipose tissue-derived hormones guided the virus-induced metabolic disorders. Proteolysis activation was revealed in SARS-CoV2 pneumonia patients. The found molecular event was accompanied by hyperglycemia induction. Multiorgan lesions manifest in in cardiac failure, which was detected in patients with ARDS. Moreover, high arterial blood pressure in patients with COVID-19 was associated with the hyperglycemia and increased ACE activity and NO ions level. Liver damage was specific for COVID-19-associated patients with severe ARDS and heart failure. Proteolysis overactivation resulting in vasoactive substances imbalance was detected in patients with the intestinal lesions. The obtained data shows the the neuropilin-dependent axis in damage prevalence in the intestine. Metabolic disorders resulting in the growth of adipose-derived tissue hormones, nitrites, and neuropilin levels was triggered by prolonged inflammation. So, the impaired metabolism and SARS-CoV2 associated hyperglycemia influence on SARS-CoV2 multiple mechanisms. Gastrointestinal manifestations in SARS-CoV2 infection was found to be related to various biochemical and molecular tools. ACE2 receptors axis is prevalent for liver damage, but NRP-1 protein (neuropilin), NO derivatives, and adipose tissue-derived hormones are essential for intestinal lesions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-022-01089-x.

Neuropilin-2 promotes lineage plasticity and progression to neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC), a lethal subset of prostate cancer, is characterized by loss of AR signaling and resulting resistance to AR-targeted therapy during neuroendocrine transdifferentiation, for which the molecular mechanisms remain unclear. Here, we report that neuropilin 2 (NRP2) is upregulated in both de novo and therapy-induced NEPC, which induces neuroendocrine markers, neuroendocrine cell morphology, and NEPC cell aggressive behavior. NRP2 silencing restricted NEPC tumor xenograft growth. Mechanistically, NRP2 engages in reciprocal crosstalk with AR, where NRP2 is transcriptionally inhibited by AR, and in turn suppresses AR signaling by downregulating the AR transcriptional program and confers resistance to enzalutamide. Moreover, NRP2 physically interacts with VEGFR2 through the intracellular SEA domain to activate STAT3 phosphorylation and subsequently SOX2, thus driving NEPC differentiation and growth. Collectively, these results characterize NRP2 as a driver of NEPC and suggest NRP2 as a potential therapeutic target in NEPC.

Adenoviral VEGF-B186R127S gene transfer induces angiogenesis and improves perfusion in ischemic heart

Vascular endothelial growth factor B (VEGF-B) is an interesting therapeutic candidate for coronary artery disease. However, it can also cause ventricular arrhythmias, potentially preventing its use in clinics. We cloned VEGF-B isoforms with different receptor binding profiles to clarify the roles of VEGFR-1 and Nrp-1 in angiogenesis and to see if angiogenic properties can be maintained while avoiding side effects. VEGF-B constructs were studied in vivo using adenovirus (Ad)-mediated intramyocardial gene transfers into the normoxic and ischemic porcine heart (n = 51). It was found that the unprocessed isoform VEGF-B186R127S is as efficient angiogenic growth factor as the native VEGF-B186 in normoxic and ischemic heart. In addition, AdVEGF-B186R127S increased myocardial perfusion reserve by 22% in ischemic heart without any side effects. AdVEGF-B127 (VEGFR-1 and Nrp-1 ligand) and AdVEGF-B109 (VEGFR-1 ligand) did not induce angiogenesis. Thus, VEGF-B186 is angiogenic only before its proteolytic processing to VEGF-B127. Only the VEGF-B186 C-terminal fragment was associated with arrhythmias.

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AdVEGF-B186R127S induces angiogenesis and improves perfusion in the ischemic heart

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No significant side effects were observed after AdVEGF-B186R127S therapy

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VEGF-B186 is angiogenic only prior to its proteolytic processing

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C-terminal fragment of VEGF-B186 is associated with ventricular arrhythmias

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.

COVID-19 and the Pediatric Nervous System: Global Collaboration to Meet a Global Need

The coronavirus disease 2019 (COVID-19) pandemic has affected mortality and morbidity across all ages, including children. It is now known that neurological manifestations of COVID-19, ranging from headaches to stroke, may involve the central and/or peripheral nervous system at any age. Neurologic involvement is also noted in the multisystem inflammatory syndrome in children, a pediatric condition that occurs weeks after infection with the causative virus of COVID-19, severe acute respiratory syndrome coronavirus 2. Knowledge about mechanisms of neurologic disease is scarce but rapidly growing. COVID-19 neurologic manifestations may have particularly adverse impacts on the developing brain. Emerging data suggest a cohort of patients with COVID-19 will have longitudinal illness affecting their cognitive, physical, and emotional health, but little is known about the long-term impact on affected children and their families. Pediatric collaboratives have begun to provide important initial information on neuroimaging manifestations and the incidence of ischemic stroke in children with COVID 19. The Global Consortium Study of Neurologic Dysfunction in COVID-19-Pediatrics, a multinational collaborative, is working to improve understanding of the epidemiology, mechanisms of neurological manifestations, and the long-term implications of COVID-19 in children and their families.

PlGF Immunological Impact during Pregnancy

During pregnancy, the mother’s immune system has to tolerate the persistence of paternal alloantigens without affecting the anti-infectious immune response. Consequently, several mechanisms aimed at preventing allograft rejection, occur during a pregnancy. In fact, the early stages of pregnancy are characterized by the correct balance between inflammation and immune tolerance, in which proinflammatory cytokines contribute to both the remodeling of tissues and to neo-angiogenesis, thus, favoring the correct embryo implantation. In addition to the creation of a microenvironment able to support both immunological privilege and angiogenesis, the trophoblast invades normal tissues by sharing the same behavior of invasive tumors. Next, the activation of an immunosuppressive phase, characterized by an increase in the number of regulatory T (Treg) cells prevents excessive inflammation and avoids fetal immuno-mediated rejection. When these changes do not occur or occur incompletely, early pregnancy failure follows. All these events are characterized by an increase in different growth factors and cytokines, among which one of the most important is the angiogenic growth factor, namely placental growth factor (PlGF). PlGF is initially isolated from the human placenta. It is upregulated during both pregnancy and inflammation. In this review, we summarize current knowledge on the immunomodulatory effects of PlGF during pregnancy, warranting that both innate and adaptive immune cells properly support the early events of implantation and placental development. Furthermore, we highlight how an alteration of the immune response, associated with PlGF imbalance, can induce a hypertensive state and lead to the pre-eclampsia (PE).

New insights into the role of co-receptor neuropilins in tumour angiogenesis and lymphangiogenesis and targeted therapy strategies

Local tumour sites lead to pathological angiogenesis and lymphangiogenesis due to malignant conditions such as hypoxia. Although VEGF and VEGFR are considered to be the main anti-tumour treatment targets, the problems of limited efficacy and observable side effects of some drugs relevant to this target still remain to be solved. Therefore, it is necessary to identify new therapeutic targets for angiogenesis or lymphangiogenesis. The neuropilin family is a class of single transmembrane glycoprotein receptors, including neuropilin1 (NRP1) and neuropilin2 (NRP2), which could act as co-receptors of VEGFA-165 and VEGFC and play a key role in promoting tumour proliferation, invasion and metastasis. In this review, we introduced the schematic diagram to visually reveal the function of NRP1 and NRP2 in enhancing the binding affinity of VEGFR2 to VEGFA-165 and VEGFR3 to VEGFC, respectively. We also discussed the signalling pathways that depend on the co-receptors NRP1 and NRP2 and some existing targeted therapeutic strategies, such as monoclonal antibodies, targeted peptides, microRNAs and small molecule inhibitors. It will contribute a vital foundation for the future research and development of new drugs targeting NRPs. HIGHLIGHTS NRP1 acts as a co-receptor with VEGFR2 and the pro-angiogenic factor VEGFA-165 to up-regulate tumour angiogenesis by promoting endothelial cells proliferation, survival, migration, invasion and by preventing of apoptosis. NRP2 acts as a co-receptor with VEGFR3 and the pro-lymphogenic factor VEGFC to facilitate tumour metastasis by promoting lymphangiogenesis. Although NRP1 and NRP2 do not have enzymatic signalling activity, the affinity of VEGFR2 for VEGFA-165 and VEGFR3 for VEGFC can increase in a co-receptor manner, as detailed in the schematic. The exclusive roles of NRP1 and NRP2 in signalling pathways are specifically described to emphasise the molecular regulatory mechanisms involved in co-receptors. Various studies have shown that the co-receptors NRP1 and NRP2 can be directly or indirectly targeted by different methods to prevent tumour angiogenesis and lymphangiogenesis. Therapeutic strategies targeting NRPs look promising soon as evidenced by preclinical and clinical studies.

The Role of Rho GTPases in VEGF Signaling in Cancer Cells

Vascular endothelial growth factors (VEGFs) consist of five molecules (VEGFA through D as well as placental growth factor) which are crucial for regulating key cellular and tissue functions. The role of VEGF and its intracellular signaling and downstream molecular pathways have been thoroughly studied. Activation of VEGF signal transduction can be initiated by the molecules' binding to two classes of transmembrane receptors: (1) the VEGF tyrosine kinase receptors (VEGF receptors 1 through 3) and (2) the neuropilins (NRP1 and 2). The involvement of Rho GTPases in modulating VEGFA signaling in both cancer cells and endothelial cells has also been well established. Additionally, different isoforms of Rho GTPases, namely, RhoA, RhoC, and RhoG, have been shown to regulate VEGF expression as well as blood vessel formation. This review article will explore how Rho GTPases modulate VEGF signaling and the consequences of such interaction on cancer progression.

Expression of NRP-1 and NRP-2 in Endometrial Cancer

Background: Neuropilins (NRPs) participate in many processes related to cancer development such as angiogenesis, lymphangiogenesis and metastasis. Although endometrial cancer is one of the most common gynecological cancers, it has not been studied in terms of NRPs expression.

Objective: The aim of this study was to investigate the potential utility of NRPs as important factors in the diagnosis and treatment of endometrial cancer.

Methods: Our study consisted of 45 women diagnosed with endometrial cancer at the following degrees of histological differentiation: G1, 17; G2, 15; G3, 13 cases. The control group included 15 women without neoplastic changes. The immunohistochemical reactions were evaluated using light microscopy.

Results: We did not detect the expression of NRP-1 and NRP-2 in the control group. NRP-1 expression was found exclusively in cancer cells. It was higher in G2 and G3 and reached about 190% of G1. NRP-2 expression was observed in the endothelium and was similar across all three cancer grades. In cancer cells, NRP-2 expression increased with the degree of histological differentiation.

Conclusion: NRP1 and NRP2 are candidates for complementary diagnostic molecular markers and promising new targets for molecular, personalized anticancer therapies.

The VEGF receptor neuropilin 2 promotes homologous recombination by stimulating YAP/TAZ-mediated Rad51 expression

Vascular endothelial growth factor (VEGF) signaling in tumor cells mediated by neuropilins (NRPs) contributes to the aggressive nature of several cancers, including triple-negative breast cancer (TNBC), independently of its role in angiogenesis. Understanding the mechanisms by which VEGF-NRP signaling contributes to the phenotype of such cancers is a significant and timely problem. We report that VEGF-NRP2 promote homologous recombination (HR) in BRCA1 wild-type TNBC cells by contributing to the expression and function of Rad51, an essential enzyme in the HR pathway that mediates efficient DNA double-strand break repair. Mechanistically, we provide evidence that VEGF-NRP2 stimulates YAP/TAZ-dependent Rad51 expression and that Rad51 is a direct YAP/TAZ-TEAD transcriptional target. We also discovered that VEGF-NRP2-YAP/TAZ signaling contributes to the resistance of TNBC cells to cisplatin and that Rad51 rescues the defects in DNA repair upon inhibition of either VEGF-NRP2 or YAP/TAZ. These findings reveal roles for VEGF-NRP2 and YAP/TAZ in DNA repair, and they indicate a unified mechanism involving VEGF-NRP2, YAP/TAZ, and Rad51 that contributes to resistance to platinum chemotherapy.

Multifaceted Role of the Placental Growth Factor (PlGF) in the Antitumor Immune Response and Cancer Progression

The sharing of molecules function that affects both tumor growth and neoangiogenesis with cells of the immune system creates a mutual interplay that impairs the host’s immune response against tumor progression. Increasing evidence shows that tumors are able to create an immunosuppressive microenvironment by recruiting specific immune cells. Moreover, molecules produced by tumor and inflammatory cells in the tumor microenvironment create an immunosuppressive milieu able to inhibit the development of an efficient immune response against cancer cells and thus fostering tumor growth and progression. In addition, the immunoediting could select cancer cells that are less immunogenic or more resistant to lysis. In this review, we summarize recent findings regarding the immunomodulatory effects and cancer progression of the angiogenic growth factor namely placental growth factor (PlGF) and address the biological complex effects of this cytokine. Different pathways of the innate and adaptive immune response in which, directly or indirectly, PlGF is involved in promoting tumor immune escape and metastasis will be described. PlGF is important for building up vascular structures and functions. Although PlGF effects on vascular and tumor growth have been widely summarized, its functions in modulating the immune intra-tumoral microenvironment have been less highlighted. In agreement with PlGF functions, different antitumor strategies can be envisioned.

Naturally occurring and synthetic constitutive-active cytokine receptors in disease and therapy

Cytokines control immune related events and are critically involved in a plethora of patho-physiological processes including autoimmunity and cancer development. Mutations which cause ligand-independent, constitutive activation of cytokine receptors are quite frequently found in diseases. Many constitutive-active cytokine receptor variants have been directly connected to disease development and mechanistically analyzed. Nature's solutions to generate constitutive cytokine receptors has been recently adopted by synthetic cytokine receptor biology, with the goal to optimize immune therapeutics. Here, CAR T cell immmunotherapy represents the first example to combine synthetic biology with genetic engineering during therapy. Hence, constitutive-active cytokine receptors are therapeutic targets, but also emerging tools to improve or modulate immunotherapeutic strategies. This review gives a comprehensive insight into the field of naturally occurring and synthetic constitutive-active cytokine receptors.

VEGFR2 survival and mitotic signaling depends on joint activation of associated C3ar1/C5ar1 and IL-6R-gp130

Purified vascular endothelial cell (EC) growth factor receptor-2 (VEGFR2) auto-phosphorylates upon VEGF-A occupation in vitro, arguing that VEGR2 confers its mitotic and viability signaling in and of itself. Herein, we show that, in ECs, VEGFR2 function requires concurrent C3a/C5a receptor (C3ar1/C5ar1) and IL-6 receptor (IL-6R)-gp130 co-signaling. C3ar1/C5ar1 or IL-6R blockade totally abolished VEGFR2 auto-phosphorylation, downstream Src, ERK, AKT, mTOR and STAT3 activation, and EC cell cycle entry. VEGF-A augmented production of C3a/C5a/IL-6 and their receptors via a two-step p-Tyk2/p-STAT3 process. Co-immunoprecipitation analyses, confocal microscopy, ligand pulldown and bioluminescence resonance energy transfer assays all indicated that the four receptors are physically interactive. Angiogenesis in murine day 5 retinas and in adult tissues was accelerated when C3ar1/C5ar1 signaling was potentiated, but repressed when it was disabled. Thus, C3ar1/C5ar1 and IL-6R-gp130 joint activation is needed to enable physiological VEGFR2 function.

VEGF/Neuropilin Signaling in Cancer Stem Cells

The function of vascular endothelial growth factor (VEGF) in cancer extends beyond angiogenesis and vascular permeability. Specifically, VEGF-mediated signaling occurs in tumor cells and this signaling contributes to key aspects of tumorigenesis including the self-renewal and survival of cancer stem cells (CSCs). In addition to VEGF receptor tyrosine kinases, the neuropilins (NRPs) are critical for mediating the effects of VEGF on CSCs, primarily because of their ability to impact the function of growth factor receptors and integrins. VEGF/NRP signaling can regulate the expression and function of key molecules that have been implicated in CSC function including Rho family guanosine triphosphatases (GTPases) and transcription factors. The VEGF/NRP signaling axis is a prime target for therapy because it can confer resistance to standard chemotherapy, which is ineffective against most CSCs. Indeed, several studies have shown that targeting either NRP1 or NRP2 can inhibit tumor initiation and decrease resistance to other therapies.

Convergence of VEGF and YAP/TAZ signaling: Implications for angiogenesis and cancer biology

Vascular endothelial growth factor (VEGF) stimulates endothelial cells to promote both developmental and pathological angiogenesis. VEGF also directly affects tumor cells and is associated with the initiation, progression, and recurrence of tumors, as well as the emergence and maintenance of cancer stem cells (CSCs). Studies have uncovered the importance of the transcriptional regulators YAP and TAZ in mediating VEGF signaling. For example, VEGF stimulates the GTPase activity of Rho family members and thereby alters cytoskeletal dynamics, which contributes to the activation of YAP and TAZ. In turn, YAP- and TAZ-mediated changes in gene expression sustain Rho family member activity and cytoskeletal effects to promote both vascular growth and remodeling in endothelial cells and the acquisition of stem-like traits in tumor cells. In this Review, we discuss how these findings further explain the pathophysiological roles of VEGF and YAP/TAZ, identify their connections to other receptor-mediated pathways, and reveal ways of therapeutically targeting their convergent signals in patients.

Jack of many trades: Multifaceted role of neuropilins in pancreatic cancer

Neuropilins (NRPs) have been described as receptors for class 3 semaphorins and coreceptors for a plethora of ligands, such as members of the vascular endothelial growth factor (VEGF) family of angiogenic cytokines and transforming growth factor (TGF). Initial studies using genetic models have indicated that neuropilin-1 (NRP-1) is essential for axonal guidance during neuronal and cardiovascular development, regulated via semaphorins and VEGF, respectively, whereas the other homolog of neuropilin, NRP-2, has been shown to play a more specific role in neuronal patterning and lymphangiogenesis. Pancreatic ductal adenocarcinoma (PDAC) remains a significant cause of cancer mortality with the lowest five-year survival rate compared to other types of cancer. Recent findings have indicated that NRPs are abundantly expressed in pancreatic cancer cell lines and pancreatic tumor tissues, where they mediate several essential cancer-initiating and cancer-promoting functional responses through their unique ability to bind multiple ligands. Specifically, NRPs have been implicated in numerous biological processes such as cancer cell proliferation, survival, invasion, and tumor growth. More recently, several other protumorigenic roles mediated by NRPs have emerged, advocating NRPs as ideal therapeutic targets against PDAC.

Expression of ID4 protein in breast cancer cells induces reprogramming of tumour-associated macrophages

Background

As crucial regulators of the immune response against pathogens, macrophages have been extensively shown also to be important players in several diseases, including cancer. Specifically, breast cancer macrophages tightly control the angiogenic switch and progression to malignancy. ID4, a member of the ID (inhibitors of differentiation) family of proteins, is associated with a stem-like phenotype and poor prognosis in basal-like breast cancer. Moreover, ID4 favours angiogenesis by enhancing the expression of pro-angiogenic cytokines interleukin-8, CXCL1 and vascular endothelial growth factor. In the present study, we investigated whether ID4 protein exerts its pro-angiogenic function while also modulating the activity of tumour-associated macrophages in breast cancer.

Methods

We performed IHC analysis of ID4 protein and macrophage marker CD68 in a triple-negative breast cancer series. Next, we used cell migration assays to evaluate the effect of ID4 expression modulation in breast cancer cells on the motility of co-cultured macrophages. The analysis of breast cancer gene expression data repositories allowed us to evaluate the ability of ID4 to predict survival in subsets of tumours showing high or low macrophage infiltration. By culturing macrophages in conditioned media obtained from breast cancer cells in which ID4 expression was modulated by overexpression or depletion, we identified changes in the expression of ID4-dependent angiogenesis-related transcripts and microRNAs (miRNAs, miRs) in macrophages by RT-qPCR.

Results

We determined that ID4 and macrophage marker CD68 protein expression were significantly associated in a series of triple-negative breast tumours. Interestingly, ID4 messenger RNA (mRNA) levels robustly predicted survival, specifically in the subset of tumours showing high macrophage infiltration. In vitro and in vivo migration assays demonstrated that expression of ID4 in breast cancer cells stimulates macrophage motility. At the molecular level, ID4 protein expression in breast cancer cells controls, through paracrine signalling, the activation of an angiogenic programme in macrophages. This programme includes both the increase of angiogenesis-related mRNAs and the decrease of members of the anti-angiogenic miR-15b/107 group. Intriguingly, these miRNAs control the expression of the cytokine granulin, whose enhanced expression in macrophages confers increased angiogenic potential.

Conclusions

These results uncover a key role for ID4 in dictating the behaviour of tumour-associated macrophages in breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-0990-2) contains supplementary material, which is available to authorized users.

VEGF-neuropilin-2 signaling promotes stem-like traits in breast cancer cells by TAZ-mediated repression of the Rac GAP β2-chimaerin

The role of vascular endothelial growth factor (VEGF) signaling in cancer is not only well known in the context of angiogenesis but also important in the functional regulation of tumor cells. Autocrine VEGF signaling mediated by its co-receptors called neuropilins (NRPs) appears to be essential for sustaining the proliferation and survival of cancer stem cells (CSCs), which are implicated in mediating tumor growth, progression, and drug resistance. Therefore, understanding the mechanisms involved in VEGF-mediated support of CSCs is critical to successfully treating cancer patients. The expression of the Hippo effector TAZ is associated with breast CSCs and confers stem cell-like properties. We found that VEGF-NRP2 signaling contributed to the activation of TAZ in various breast cancer cells, which mediated a positive feedback loop that promoted mammosphere formation. VEGF-NRP2 signaling activated the GTPase Rac1, which inhibited the Hippo kinase LATS, thus leading to TAZ activity. In a complex with the transcription factor TEAD, TAZ then bound and repressed the promoter of the gene encoding the Rac GTPase-activating protein (Rac GAP) β2-chimaerin. By activating GTP hydrolysis, Rac GAPs effectively turn off Rac signaling; hence, the TAZ-mediated repression of β2-chimaerin resulted in sustained Rac1 activity in CSCs. Depletion of β2-chimaerin in non-CSCs increased Rac1 activity, TAZ abundance, and mammosphere formation. Analysis of a breast cancer patient database revealed an inverse correlation between β2-chimaerin and TAZ expression in tumors. Our findings highlight an unexpected role for β2-chimaerin in a feed-forward loop of TAZ activation and the acquisition of CSC properties.

Neuroimmune semaphorins as costimulatory molecules and beyond

Several neuronal guidance proteins, known as semaphorin molecules, function in the immune system. This dual tissue performance has led to them being defined as "neuroimmune semaphorins". They have been shown to regulate T cell activation by serving as costimulatory molecules. Similar to classical costimulatory molecules, neuroimmune semaphorins are either constitutively or inducibly expressed on immune cells. In contrast to the classical costimulatory molecule function, the action of neuroimmune semaphorins requires the presence of two signals, the first one provided by TCR/MHC engagement, and the second one provided by B7/CD28 interaction. Thus, neuroimmune semaphorins serve as a "signal three" for immune cell activation and regulate the overall intensity of immune response. The current knowledge on their structures, multiple receptors, specific cell/tissue/organ expression, and distinct functions in different diseases are summarized and discussed in this review.

Biology of Vascular Endothelial Growth Factor C in the Morphogenesis of Lymphatic Vessels

Because virtually all tissues contain blood vessels, the importance of hemevascularization has been long recognized in regenerative medicine and tissue engineering. However, the lymphatic vasculature has only recently become a subject of interest. Central to the task of growing a lymphatic network are lymphatic endothelial cells (LECs), which constitute the innermost layer of all lymphatic vessels. The central molecule that directs proliferation and migration of LECs during embryogenesis is vascular endothelial growth factor C (VEGF-C). VEGF-C is therefore an important ingredient for LEC culture and attempts to (re)generate lymphatic vessels and networks. During its biosynthesis VEGF-C undergoes a stepwise proteolytic processing, during which its properties and affinities for its interaction partners change. Many of these fundamental aspects of VEGF-C biosynthesis have only recently been uncovered. So far, most—if not all—applications of VEGF-C do not discriminate between different forms of VEGF-C. However, for lymphatic regeneration and engineering purposes, it appears mandatory to understand these differences, since they relate, e.g., to important aspects such as biodistribution and receptor activation potential. In this review, we discuss the molecular biology of VEGF-C as it relates to the growth of LECs and lymphatic vessels. However, the properties of VEGF-C are similarly relevant for the cardiovascular system, since both old and recent data show that VEGF-C can have a profound effect on the blood vasculature.

Vascular endothelial growth factor-B: Impact on physiology and pathology

Angiogenesis plays an important role in controlling tissue development and maintaining normal tissue function. Dysregulated angiogenesis is implicated in the pathogenesis of a variety of diseases, particularly diabetes, cancers, and neurodegenerative disorders. As the major regulator of angiogenesis, the vascular endothelial growth factor (VEGF) family is composed of a group of crucial members including VEGF-B. While the physiological roles of VEGF-B remain debatable, increasing evidence suggests that this protein is able to protect certain type of cells from apoptosis under pathological conditions. More importantly, recent studies reveal that VEGF-B is involved in lipid transport and energy metabolism, implicating this protein in obesity, diabetes and related metabolic complications. This article summarizes the current knowledge and understanding of VEGF-B in physiology and pathology, and shed light on the therapeutic potential of this crucial protein.

CD133+ cancer stem cells promoted by VEGF accelerate the recurrence of hepatocellular carcinoma

The role of cancer stem cells (CSCs) in inducing the recurrence of hepatocellular carcinoma (HCC) after radiofrequency ablation (RFA) remains unclear. Here, we found that a dramatic increase in plasma vascular endothelial growth factor (VEGF) and an induction of local CD133⁺ CSCs are associated with early HCC recurrence, suggesting that VEGF expression and tumour stemness contribute to the relapse. In vitro studies demonstrated that VEGF, via activation of VEGFR2, increased the number of CD133⁺ CSCs and enhanced their capacity for self-renewal by inducing the expression of Nanog. In vivo studies further demonstrated that VEGF-treated CD133⁺ CSCs formed tumours larger than those developing from unstimulated cells and VEGF pre-treatment increased the tumorigenic cell frequency of primary HCC cells dependently on the presence of Nanog and VEGFR2. In HCC tissue derived from patients with early recurrence, almost all CD133⁺ cells were Nanog and p-VEGFR2 positive, suggesting that activation of VEGFR2 is critical for RFA-induced tumour stemness in HCC. In summary, RFA-induced VEGF promotes tumour stemness and accelerates tumourigenesis in HCC in a manner dependent on Nanog and VEGFR2, which is valuable for the prediction of HCC recurrence after RFA and the development of novel therapeutics.

Exploring Novel Methods for Modulating Tumor Blood Vessels in Cancer Treatment

Several studies have explored the potential of targeting tumor angiogenesis in cancer treatment. Anti-angiogenesis monotherapy, which reduces blood vessel numbers, may still hold some promise in cancer treatment, but thus far it has only provided a modest effect on overall survival benefits. When combined with standard chemotherapies, some significant improvements in cancer therapy have been reported. However, anti-angiogenesis therapies can have undesirable effects, including the induction of tumor hypoxia and reduction of delivery of chemotherapeutic drugs. Interestingly, anti-angiogenic drugs, such as bevacizumab, when used at lower doses, can actually induce vascular normalization (that is, they improve blood vessel function and flow) and potentially enhance co-administrated chemotherapeutic drug delivery. Unfortunately, vascular normalization is a difficult approach to apply in clinical settings. Thus, there is an urgent need to explore new approaches for modulating the tumor vasculature. Here, we explore how vascular promotion strategies (which enhance blood vessel numbers and leakiness) may be optimized for combination therapies as an alternative option for cancer treatment.

Relationship of VEGF/VEGFR with immune and cancer cells: staggering or forward?

Vascular endothelial growth factor (VEGF) is primarily known as a proangiogenic factor and is one of the most important growth and survival factors affecting the vascular endothelium. However, recent studies have shown that VEGF also plays a vital role in the immune environment. In addition to the traditional growth factor role of VEGF and VEGF receptors (VEGFRs), they have a complicated relationship with various immune cells. VEGF also reportedly inhibits the differentiation and function of immune cells during hematopoiesis. Dendritic cells (DCs), macrophages, and lymphocytes further express certain types of VEGF receptors. VEGF can be secreted as well by tumor cells through the autocrine pathway and can stimulate the function of cancer stemness. This review will provide a paradigm shift in our understanding of the role of VEGF/VEGFR signaling in the immune and cancer environment.

Lack of VEGFR2 signaling causes maldevelopment of the intestinal microvasculature and facilitates necrotizing enterocolitis in neonatal mice

The pathogenesis of necrotizing enterocolitis (NEC), a common gastrointestinal disease affecting premature infants, remains poorly understood. We previously found that intestinal VEGF-A expression is decreased in human NEC samples and in a neonatal mouse NEC model prior to detectable histological injury. Therefore, we hypothesized that lack of VEGF receptor 2 (VEGFR2) signaling facilitates neonatal intestinal injury by impairing intestinal microvasculature development. Here, we found that intestinal VEGF-A and its receptor, VEGFR2, were highly expressed at the end of fetal life and significantly decreased after birth in mice. Furthermore, selective inhibition of VEGFR2 kinase activity and exposure to a neonatal NEC protocol significantly decreased the density of the intestinal microvascular network, which was further reduced when both interventions were provided together. Furthermore, VEGFR2 inhibition resulted in greater mortality and incidence of severe injury in pups submitted to the NEC model. The percentage of lamina propria endothelial cells was decreased during NEC induction, and further decreased when VEGFR2 signaling was inhibited. This was associated with decreased endothelial cell proliferation rather than apoptosis. In conclusion, we found that VEGF-A and VEGFR2 proteins are highly expressed in the intestine before birth, and are significantly downregulated in the immediate neonatal period. Furthermore, VEGFR2 signaling is necessary to maintain the integrity of the intestinal mucosal microvasculature during the postnatal period and lack of VEGFR2 signaling predisposes to NEC in neonatal mice.

DNA Methylation in Newborns and Maternal Smoking in Pregnancy: Genome-wide Consortium Meta-analysis

Epigenetic modifications, including DNA methylation, represent a potential mechanism for environmental impacts on human disease. Maternal smoking in pregnancy remains an important public health problem that impacts child health in a myriad of ways and has potential lifelong consequences. The mechanisms are largely unknown, but epigenetics most likely plays a role. We formed the Pregnancy And Childhood Epigenetics (PACE) consortium and meta-analyzed, across 13 cohorts (n = 6,685), the association between maternal smoking in pregnancy and newborn blood DNA methylation at over 450,000 CpG sites (CpGs) by using the Illumina 450K BeadChip. Over 6,000 CpGs were differentially methylated in relation to maternal smoking at genome-wide statistical significance (false discovery rate, 5%), including 2,965 CpGs corresponding to 2,017 genes not previously related to smoking and methylation in either newborns or adults. Several genes are relevant to diseases that can be caused by maternal smoking (e.g., orofacial clefts and asthma) or adult smoking (e.g., certain cancers). A number of differentially methylated CpGs were associated with gene expression. We observed enrichment in pathways and processes critical to development. In older children (5 cohorts, n = 3,187), 100% of CpGs gave at least nominal levels of significance, far more than expected by chance (p value < 2.2 × 10(-16)). Results were robust to different normalization methods used across studies and cell type adjustment. In this large scale meta-analysis of methylation data, we identified numerous loci involved in response to maternal smoking in pregnancy with persistence into later childhood and provide insights into mechanisms underlying effects of this important exposure.

VEGF-C and TGF-β reciprocally regulate mesenchymal stem cell commitment to differentiation into lymphatic endothelial or osteoblastic phenotypes

The direction of mesenchymal stem cell (MSC) differentiation is regulated by stimulation with various growth factors and cytokines. We recently established MSC lines, [transforming growth factor-β (TGF-β)-responsive SG‑2 cells, bone morphogenetic protein (BMP)-responsive SG‑3 cells, and TGF-β/BMP-non-responsive SG‑5 cells], derived from the bone marrow of green fluorescent protein-transgenic mice. In this study, to compare gene expression profiles in these MSC lines, we used DNA microarray analysis to characterize the specific gene expression profiles observed in the TGF-β-responsive SG‑2 cells. Among the genes that were highly expressed in the SG‑2 cells, we focused on vascular endothelial growth factor (VEGF) receptor 3 (VEGFR3), the gene product of FMS-like tyrosine kinase 4 (Flt4). We found that VEGF-C, a specific ligand of VEGFR3, significantly induced the cell proliferative activity, migratory ability (as shown by Transwell migration assay), as well as the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 in the SG‑2 cells. Additionally, VEGF-C significantly increased the expression of prospero homeobox 1 (Prox1) and lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1), which are lymphatic endothelial cell markers, and decreased the expression of osteogenic differentiation marker genes in these cells. By contrast, TGF-β significantly increased the expression of early-phase osteogenic differentiation marker genes in the SG‑2 cells and markedly decreased the expression of lymphatic endothelial cell markers. The findings of our study strongly suggest the following: i) that VEGF-C promotes the proliferative activity and migratory ability of MSCs; and ii) VEGF-C and TGF-β reciprocally regulate MSC commitment to differentiation into lymphatic endothelial or osteoblastic phenotypes, respectively. Our findings provide new insight into the molecular mechanisms underlying the regenerative ability of MSCs.

Endothelial progenitor cells in tumor angiogenesis: another brick in the wall

Until 15 years ago, vasculogenesis, the formation of new blood vessels from undifferentiated cells, was thought to occur only during embryonic development. The discovery of circulating cells that are able to promote vascular regeneration and repair—the so-called endothelial progenitor cells (EPCs)—changed that, and EPCs have since been studied extensively. It is already known that EPCs include many subtypes of cells that play a variety of roles in promoting vascular growth. Some EPCs are destined to differentiate into endothelial cells, whereas others are capable of promoting and sustaining angiogenesis through paracrine mechanisms. Vasculogenesis and angiogenesis might constitute complementary mechanisms for postnatal neovascularization, and EPCs could be at the core of this process. Although the formation of new blood vessels from preexisting vasculature plays a beneficial role in many physiological processes, such as wound healing, it also contributes to tumor growth and metastasis. However, many aspects of the role played by EPCs in tumor angiogenesis remain unclear. This review aims to address the main aspects of EPCs differentiation and certain characteristics of their main function, especially in tumor angiogenesis, as well as the potential clinical applications.

Semaphorin signaling in cardiovascular development

Semaphorins were originally identified as neuronal guidance molecules mediating their attractive or repulsive signals by forming complexes with plexin and neuropilin receptors. Subsequent research has identified functions for semaphorin signaling in many organs and tissues outside of the nervous system. Vital roles for semaphorin signaling in vascular patterning and cardiac morphogenesis have been demonstrated, and impaired semaphorin signaling has been associated with various human cardiovascular disorders, including persistent truncus arteriosus, sinus bradycardia and anomalous pulmonary venous connections. Here, we review the functions of semaphorins and their receptors in cardiovascular development and disease and highlight important recent discoveries in the field.

Comparative Analysis of Glycogene Expression in Different Mouse Tissues Using RNA-Seq Data

Glycogenes regulate a wide array of biological processes in the development of organisms as well as different diseases such as cancer, primary open-angle glaucoma, and renal dysfunction. The objective of this study was to explore the role of differentially expressed glycogenes (DEGGs) in three major tissues such as brain, muscle, and liver using mouse RNA-seq data, and we identified 579, 501, and 442 DEGGs for brain versus liver (BvL579), brain versus muscle (BvM501), and liver versus muscle (LvM442) groups. DAVID functional analysis suggested inflammatory response, glycosaminoglycan metabolic process, and protein maturation as the enriched biological processes in BvL579, BvM501, and LvM442, respectively. These DEGGs were then used to construct three interaction networks by using GeneMANIA, from which we detected potential hub genes such as PEMT and HPXN (BvL579), IGF2 and NID2 (BvM501), and STAT6 and FLT1 (LvM442), having the highest degree. Additionally, our community analysis results suggest that the significance of immune system related processes in liver, glycosphingolipid metabolic processes in the development of brain, and the processes such as cell proliferation, adhesion, and growth are important for muscle development. Further studies are required to confirm the role of predicted hub genes as well as the significance of biological processes.

Mesenchymal stem cells as cellular vectors for pediatric neurological disorders

Lysosomal storage diseases are a heterogeneous group of hereditary disorders characterized by a deficiency in lysosomal function. Although these disorders differ in their etiology and phenotype those that affect the nervous system generally manifest as a profound deterioration in neurologic function with age. Over the past several decades implementation of various treatment regimens including bone marrow and cord blood cell transplantation, enzyme replacement, and substrate reduction therapy have proved effective for managing some clinical manifestations of these diseases but their ability to ameliorate neurologic complications remains unclear. Consequently, there exists a need to develop alternative therapies that more effectively target the central nervous system. Recently, direct intracranial transplantation of tissue-specific stem and progenitor cells has been explored as a means to reconstitute metabolic deficiencies in the CNS. In this chapter we discuss the merits of bone marrow-derived mesenchymal stem cells (MSCs) for this purpose. Originally identified as progenitors of connective tissue cell lineages, recent findings have revealed several novel aspects of MSC biology that make them attractive as therapeutic agents in the CNS. We relate these advances in MSC biology to their utility as cellular vectors for treating neurologic sequelae associated with pediatric neurologic disorders.

Delayed administration of a bio-engineered zinc-finger VEGF-A gene therapy is neuroprotective and attenuates allodynia following traumatic spinal cord injury

Following spinal cord injury (SCI) there are drastic changes that occur in the spinal microvasculature, including ischemia, hemorrhage, endothelial cell death and blood-spinal cord barrier disruption. Vascular endothelial growth factor-A (VEGF-A) is a pleiotropic factor recognized for its pro-angiogenic properties; however, VEGF has recently been shown to provide neuroprotection. We hypothesized that delivery of AdV-ZFP-VEGF--an adenovirally delivered bio-engineered zinc-finger transcription factor that promotes endogenous VEGF-A expression--would result in angiogenesis, neuroprotection and functional recovery following SCI. This novel VEGF gene therapy induces the endogenous production of multiple VEGF-A isoforms; a critical factor for proper vascular development and repair. Briefly, female Wistar rats--under cyclosporin immunosuppression--received a 35 g clip-compression injury and were administered AdV-ZFP-VEGF or AdV-eGFP at 24 hours post-SCI. qRT-PCR and Western Blot analysis of VEGF-A mRNA and protein, showed significant increases in VEGF-A expression in AdV-ZFP-VEGF treated animals (p<0.001 and p<0.05, respectively). Analysis of NF200, TUNEL, and RECA-1 indicated that AdV-ZFP-VEGF increased axonal preservation (p<0.05), reduced cell death (p<0.01), and increased blood vessels (p<0.01), respectively. Moreover, AdV-ZFP-VEGF resulted in a 10% increase in blood vessel proliferation (p<0.001). Catwalk™ analysis showed AdV-ZFP-VEGF treatment dramatically improves hindlimb weight support (p<0.05) and increases hindlimb swing speed (p<0.02) when compared to control animals. Finally, AdV-ZFP-VEGF administration provided a significant reduction in allodynia (p<0.01). Overall, the results of this study indicate that AdV-ZFP-VEGF administration can be delivered in a clinically relevant time-window following SCI (24 hours) and provide significant molecular and functional benefits.

Roles of vascular endothelial growth factor in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal devastating neurodegenerative disorder, involving progressive degeneration of motor neurons in spinal cord, brainstem, and motor cortex. Riluzole is the only drug approved in ALS but it only confers a modest improvement in survival. In spite of a high number of clinical trials no other drug has proved effectiveness. Recent studies support that vascular endothelial growth factor (VEGF), originally described as a key angiogenic factor, also plays a key role in the nervous system, including neurogenesis, neuronal survival, neuronal migration, and axon guidance. VEGF has been used in exploratory clinical studies with promising results in ALS and other neurological disorders. Although VEGF is a very promising compound, translating the basic science breakthroughs into clinical practice is the major challenge ahead. VEGF-B, presenting a single safety profile, protects motor neurons from degeneration in ALS animal models and, therefore, it will be particularly interesting to test its effects in ALS patients. In the present paper the authors make a brief description of the molecular properties of VEGF and its receptors and review its different features and therapeutic potential in the nervous system/neurodegenerative disease, particularly in ALS.

Placental development during early pregnancy in sheep: effects of embryo origin on vascularization

Utero-placental growth and vascular development are critical for pregnancy establishment that may be altered by various factors including assisted reproductive technologies (ART), nutrition, or others, leading to compromised pregnancy. We hypothesized that placental vascularization and expression of angiogenic factors are altered early in pregnancies after transfer of embryos created using selected ART methods. Pregnancies were achieved through natural mating (NAT), or transfer of embryos from NAT (NAT-ET), or IVF or in vitro activation (IVA). Placental tissues were collected on day 22 of pregnancy. In maternal caruncles (CAR), vascular cell proliferation was less (P<0.05) for IVA than other groups. Compared with NAT, density of blood vessels was less (P<0.05) for IVF and IVA in fetal membranes (FM) and for NAT-ET, IVF, and IVA in CAR. In FM, mRNA expression was decreased (P<0.01-0.08) in NAT-ET, IVF, and IVA compared with NAT for vascular endothelial growth factor (VEGF) and its receptor FLT1, placental growth factor (PGF), neuropilin 1 (NP1) and NP2, angiopoietin 1 (ANGPT1) and ANGPT2, endothelial nitric oxide synthase 3 (NOS3), hypoxia-inducible factor 1A (HIF1A), fibroblast growth factor 2 (FGF2), and its receptor FGFR2. In CAR, mRNA expression was decreased (P<0.01-0.05) in NAT-ET, IVF, and IVA compared with NAT for VEGF, FLT1, PGF, ANGPT1, and TEK. Decreased mRNA expression for 12 of 14 angiogenic factors across FM and CAR in NAT-ET, IVF, and IVA pregnancies was associated with reduced placental vascular development, which would lead to poor placental function and compromised fetal and placental growth and development.

Paxillin controls endothelial cell migration and tumor angiogenesis by altering neuropilin 2 expression

Although a number of growth factors and receptors are known to control tumor angiogenesis, relatively little is known about the mechanism by which these factors influence the directional endothelial cell migration required for cancer microvessel formation. Recently, it has been shown that the focal adhesion protein paxillin is required for directional migration of fibroblasts in vitro. Here, we show that paxillin knockdown enhances endothelial cell migration in vitro and stimulates angiogenesis during normal development and in response to tumor angiogenic factors in vivo. Paxillin produces these effects by decreasing expression of neuropilin 2 (NRP2). Moreover, soluble factors secreted by tumors that stimulate vascular ingrowth, including vascular endothelial growth factor (VEGF), also decrease endothelial cell expression of paxillin and NRP2, and overexpression of NRP2 reverses these effects. These results suggest that the VEGF-paxillin-NRP2 pathway could represent a new therapeutic target for cancer and other angiogenesis-related diseases.

VEGF targets the tumour cell

The function of vascular endothelial growth factor (VEGF) in cancer is not limited to angiogenesis and vascular permeability. VEGF-mediated signalling occurs in tumour cells, and this signalling contributes to key aspects of tumorigenesis, including the function of cancer stem cells and tumour initiation. In addition to VEGF receptor tyrosine kinases, the neuropilins are crucial for mediating the effects of VEGF on tumour cells, primarily because of their ability to regulate the function and the trafficking of growth factor receptors and integrins. This has important implications for our understanding of tumour biology and for the development of more effective therapeutic approaches.

Angiogenesis in liver regeneration and fibrosis: "a double-edged sword"

Angiogenesis, defined as the formation of new microvasculature from preexisting blood vessels and mature endothelial cells, plays a major role in wound healing and scar formation, and it is associated with inflammatory responses. Angiogenesis can occur in physiological conditions, such as during liver regeneration, and in pathological situations, such as during the progression of fibrosis to cirrhosis and also during tumor angiogenesis. Cellular cross-talk among liver sinusoidal endothelial cells (LSECs), hepatic stellate cells and hepatocytes is believed to play an important role in the angiogenesis process during both liver regeneration and development of cirrhosis. In addition to mature endothelial cells, bone marrow (BM)-derived circulating endothelial progenitor cells (EPCs) have been recently identified for their contribution to post-natal vasculogenesis/angiogenesis. In vivo, EPCs are mobilized into the peripheral blood in response to tissue ischemia or traumatic injury, migrate to the sites of injured endothelium and differentiate into mature endothelial cells. In our recent studies, we have explored the role of EPC-mediated angiogenesis in liver regeneration and/or cirrhosis. Results have demonstrated significantly increased endogenous levels of circulating EPCs in cirrhotic patients in comparison to the controls. Also, EPCs from cirrhotic patients have been observed to stimulate substantial angiogenesis by resident LSECs in vitro via paracrine factors such as vascular endothelial growth factor and platelet-derived growth factor. This review gives an overview of the angiogenesis process in liver regeneration and disease and discusses a new mechanism for intrahepatic angiogenesis mediated by BM-derived EPCs.

Inhibition of stromal PlGF suppresses the growth of prostate cancer xenografts

The growth and vascularization of prostate cancer is dependent on interactions between cancer cells and supporting stromal cells. The primary stromal cell type found in prostate tumors is the carcinoma-associated fibroblast, which produces placental growth factor (PlGF). PlGF is a member of the vascular endothelial growth factor (VEGF) family of angiogenic molecules and PlGF mRNA levels increase after androgen deprivation therapy in prostate cancer. In this study, we show that PlGF has a direct dose-dependent proliferative effect on human PC-3 prostate cancer cells in vitro and fibroblast-derived PlGF increases PC-3 proliferation in co-culture. In xenograft tumor models, intratumoral administration of murine PlGF siRNA reduced stromal-derived PlGF expression, reduced tumor burden and decreased the number of Ki-67 positive proliferating cells associated with reduced vascular density. These data show that targeting stromal PlGF expression may represent a therapeutic target for the treatment of prostate cancer.

GLI1 regulates a novel neuropilin-2/α6β1 integrin based autocrine pathway that contributes to breast cancer initiation

The characterization of cells with tumour initiating potential is significant for advancing our understanding of cancer and improving therapy. Aggressive, triple-negative breast cancers (TNBCs) are enriched for tumour-initiating cells (TICs). We investigated that hypothesis that VEGF receptors expressed on TNBC cells mediate autocrine signalling that contributes to tumour initiation. We discovered the VEGF receptor neuropilin-2 (NRP2) is expressed preferentially on TICs, involved in the genesis of TNBCs and necessary for tumour initiation. The mechanism by which NRP2 signalling promotes tumour initiation involves stimulation of the α6β1 integrin, focal adhesion kinase-mediated activation of Ras/MEK signalling and consequent expression of the Hedgehog effector GLI1. GLI1 also induces BMI-1, a key stem cell factor, and it enhances NRP2 expression and the function of α6β1, establishing an autocrine loop. NRP2 can be targeted in vivo to retard tumour initiation. These findings reveal a novel autocrine pathway involving VEGF/NRP2, α6β1 and GLI1 that contributes to the initiation of TNBC. They also support the feasibility of NRP2-based therapy for the treatment of TNBC that targets and impedes the function of TICs.

Enhancing integrin function by VEGF/neuropilin signaling: implications for tumor biology

This review advances the hypothesis that the ability of integrins to engage their extracellular matrix ligands and signal can be regulated in tumor cells by vascular endothelial growth factor (VEGF), a major angiogenic factor that also has direct effects on the function of tumor cells. More specifically, we will discuss how neuropilins (NRPs), a distinct class of VEGF receptors, enable the function of specific integrins that contribute to tumor initiation and progression.

Angiogenesis in metastatic colorectal cancer and the benefits of targeted therapy

The diverse pathways and molecules involved in angiogenesis, the formation of new blood vessels, have been targeted for the treatment of colorectal and other cancers. Vascular endothelial growth factor (VEGF)-A binding to VEGF receptor (VEGFR)-2 is believed to be the key signaling pathway mediating angiogenesis. Other VEGF pathways involved in angiogenesis include VEGF-A, VEGF-B, and placental growth factor binding to VEGFR-1, and VEGF-C and VEGF-D binding to VEGFR-2 and VEGFR-3. VEGF signaling also intersects with other pathways, including angiopoietin/Tie, Notch, hypoxia-inducible factor, and integrin pathways. The roles of these pathways in tumor angiogenesis and in various human cancers will be explored in this article. In addition, preclinical and clinical data on bevacizumab, aflibercept (known as ziv-aflibercept in the US), and investigational antiangiogenic agents in development for the treatment of colorectal and other cancers will be reviewed.

Motoneuronal Sema3C is essential for setting stereotyped motor tract positioning in limb-derived chemotropic semaphorins

The wiring of neuronal circuits requires complex mechanisms to guide axon subsets to their specific target with high precision. To overcome the limited number of guidance cues, modulation of axon responsiveness is crucial for specifying accurate trajectories. We report here a novel mechanism by which ligand/receptor co-expression in neurons modulates the integration of other guidance cues by the growth cone. Class 3 semaphorins (Sema3 semaphorins) are chemotropic guidance cues for various neuronal projections, among which are spinal motor axons navigating towards their peripheral target muscles. Intriguingly, Sema3 proteins are dynamically expressed, forming a code in motoneuron subpopulations, whereas their receptors, the neuropilins, are expressed in most of them. Targeted gain- and loss-of-function approaches in the chick neural tube were performed to enable selective manipulation of Sema3C expression in motoneurons. We show that motoneuronal Sema3C regulates the shared Sema3 neuropilin receptors Nrp1 and Nrp2 levels in opposite ways at the growth cone surface. This sets the respective responsiveness to exogenous Nrp1- and Nrp2-dependent Sema3A, Sema3F and Sema3C repellents. Moreover, in vivo analysis revealed a context where this modulation is essential. Motor axons innervating the forelimb muscles are exposed to combined expressions of semaphorins. We show first that the positioning of spinal nerves is highly stereotyped and second that it is compromised by alteration of motoneuronal Sema3C. Thus, the role of the motoneuronal Sema3 code could be to set population-specific axon sensitivity to limb-derived chemotropic Sema3 proteins, therefore specifying stereotyped motor nerve trajectories in their target field.

PlGF: a multitasking cytokine with disease-restricted activity

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that also comprises VEGF-A (VEGF), VEGF-B, VEGF-C, and VEGF-D. Unlike VEGF, PlGF is dispensable for development and health but has diverse nonredundant roles in tissue ischemia, malignancy, inflammation, and multiple other diseases. Genetic and pharmacological gain-of-function and loss-of-function studies have identified molecular mechanisms of this multitasking cytokine and characterized the therapeutic potential of delivering or blocking PlGF for various disorders.

VEGF/neuropilin-2 regulation of Bmi-1 and consequent repression of IGF-IR define a novel mechanism of aggressive prostate cancer

We show that the VEGF receptor neuropilin-2 (NRP2) is associated with high-grade, PTEN-null prostate cancer and that its expression in tumor cells is induced by PTEN loss as a consequence of c-Jun activation. VEGF/NRP2 signaling represses insulin-like growth factor-1 receptor (IGF-IR) expression and signaling, and the mechanism involves Bmi-1-mediated transcriptional repression of the IGF-IR. This mechanism has significant functional and therapeutic implications that were evaluated. IGF-IR expression positively correlates with PTEN and inversely correlates with NRP2 in prostate tumors. NRP2 is a robust biomarker for predicting response to IGF-IR therapy because prostate carcinomas that express NRP2 exhibit low levels of IGF-IR. Conversely, targeting NRP2 is only modestly effective because NRP2 inhibition induces compensatory IGF-IR signaling. Inhibition of both NRP2 and IGF-IR, however, completely blocks tumor growth in vivo.