VEGF-A splice variants bind VEGFRs with differential affinities

VEGF/VEGFR axis and its signaling in melanoma: Current knowledge toward therapeutic targeting agents and future perspectives

Melanoma is responsible for most skin cancer-associated deaths globally. The progression of melanoma is influenced by a number of pathogenic processes. Understanding the VEGF/VEGFR axis, which includes VEGF-A, PlGF, VEGF-B, VEGF-C, and VEGF-D and their receptors, VEGFR-1, VEGFR-2, and VEGFR-3, is of great importance in melanoma due to its crucial role in angiogenesis. This axis generates multifactorial and complex cellular signaling, engaging the MAPK/ERK, PI3K/AKT, PKC, PLC-γ, and FAK signaling pathways. Melanoma cell growth and proliferation, migration and metastasis, survival, and acquired resistance to therapy are influenced by this axis. The VEGF/VEGFR axis was extensively examined for their potential as diagnostic/prognostic biomarkers in melanoma patients and results showed that VEGF overexpression can be associated with unfavorable prognosis, higher level of tumor invasion and poor response to therapy. MicroRNAs linking to the VEGF/VEGFR axis were identified and, in this review, divided into two categories according to their functions, some of them promote melanoma angiogenesis (promotive group) and some restrict melanoma angiogenesis (protective group). In addition, the approach of treating melanoma by targeting the VEGF/VEGFR axis has garnered significant interest among researchers. These agents can be divided into two main groups: anti-VEGF and VEGFR inhibitors. These therapeutic options may be a prominent step along with the modern targeting and immune therapies for better coverage of pathological processes leading to melanoma progression and therapy resistance.

Full-Length Single Protein Molecules Tracking and Counting in Thin Silicon Channels

Emerging single-molecule protein sensing techniques are ushering in a transformative era in biomedical research. Nevertheless, challenges persist in realizing ultra-fast full-length protein sensing, including loss of molecular integrity due to protein fragmentation, biases introduced by antibodies affinity, identification of proteoforms, and low throughputs. Here, a single-molecule method for parallel protein separation and tracking is introduced, yielding multi-dimensional molecular properties used for their identification. Proteins are tagged by chemo-selective dual amino-acid specific labels and are electrophoretically separated by their mass/charge in custom-designed thin silicon channel with subwavelength height. This approach allows analysis of thousands of individual proteins within a few minutes by tracking their motion during the migration. The power of the method is demonstrated by quantifying a cytokine panel for host-response discrimination between viral and bacterial infections. Moreover, it is shown that two clinically-relevant splice isoforms of Vascular endothelial growth factor (VEGF) can be accurately quantified from human serum samples. Being non-destructive and compatible with full-length intact proteins, this method opens up ways for antibody-free single-protein molecule quantification.

Recent trends in aptamer-based nanobiosensors for detection of vascular endothelial growth factors (VEGFs) biomarker: A review

Vascular endothelial growth factor (VEGF) is a remarkable cytokine that plays an important role in regulating vascular formation during the angiogenesis process. Therefore, real-time detection and quantification of VEGF is essential for clinical diagnosis and treatment due to its overexpression in various tumors. Among various sensing strategies, the aptamer-based sensors in combination with biological molecules improve the detection ability VEGFs. Aptamers are suitable biological recognition agents for the preparation of sensitive and reproducible aptasensors (Apt-sensors) due to their low immunogenicity, simple and straightforward chemical modification, and high resistance to denaturation. Here, a summary of the strategies for immobilization of aptamers (e.g., direct or self-assembled monolayer (SAM) attachment, etc.) on different types of electrodes was provided. Moreover, we discussed nanoparticle deposition techniques and surface modification methods used for signal amplification in the detection of VEGF. Furthermore, we are investigating various types of optical and electrochemical Apt-sensors used to improve sensor characterization in the detection of VEGF biomarkers.

Numerical and analytical analysis of an ultrahigh sensitive surface plasmon resonance sensor based on a black phosphorene/graphene heterostructure

In this study, a surface plasmon resonance biosensor using angular interrogation based on a black phosphorene (BP) and graphene (G) heterostructure as two-dimensional materials are designed to enhance the sensitivity of conventional biosensors. The proposed structure is composed of eight layers: FK51A coupling prism, silver (Ag) thin film as the plasmonic metal, gold (Au) nanolayer in a protective role, BP nanosheets as an evanescent field enhancer, G monolayer as an immobilization process facilitator, DNA aptamer as biorecognition element, and phosphate buffered saline as a running buffer and sensing medium. To evaluate the performance of the proposed biosensor, analytical parameters such as minimum reflectivity (R m i n ), sensitivity, as well as the full width at half-maximum (FWHM), detection accuracy (DA), and quality factor (QF) are systematically assessed by the use of the transfer matrix method analytically and the finite-difference time-domain method numerically, to validate each other. It is observed that the structure has been optimized with 1.49 (RIU) for the coupling prism and the heterostructure T i O 2/A g/A u/B P/G thicknesses of 65/35/1/3.18/0.34 nm, respectively. It was revealed that the proposed biosensor offered the sensitivity of 356 (°/RIU), QF of 42.4 (R I U -1), R m i n of 0.07 (a.u), FWHM of 8.3 (degree), and DA of 0.22 (unitless) and outperformed those of other results published up to now from the sensitivity point of view.

Aptamers Versus Vascular Endothelial Growth Factor (VEGF): A New Battle against Ovarian Cancer

Cancer is one of the diseases that causes a high mortality as it involves unregulated and abnormal cell growth proliferation that can manifest in any body region. One of the typical ovarian cancer symptoms is damage to the female reproductive system. The death rate can be reduced through early detection of the ovarian cancer. Promising probes that can detect ovarian cancer are suitable aptamers. Aptamers, i.e., so-called chemical antibodies, have a strong affinity for the target biomarker and can typically be identified starting from a random library of oligonucleotides. Compared with other probes, ovarian cancer targeting using aptamers has demonstrated superior detection effectiveness. Various aptamers have been selected to detect the ovarian tumor biomarker, vascular endothelial growth factor (VEGF). The present review highlights the development of particular aptamers that target VEGF and detect ovarian cancer at its earliest stages. The therapeutic efficacy of aptamers in ovarian cancer treatment is also discussed.

New advances in the research of clinical treatment and novel anticancer agents in tumor angiogenesis

In 1971, Folkman proposed that tumors could be limited to very small sizes by blocking angiogenesis. Angiogenesis is the generation of new blood vessels from pre-existing vessels, considered to be one of the important processes in tumor growth and metastasis. Angiogenesis is a complex process regulated by various factors and involves many secreted factors and signaling pathways. Angiogenesis is important in the transport of oxygen and nutrients to the tumor during tumor development. Therefore, inhibition of angiogenesis has become an important strategy in the clinical management of many solid tumors. Combination therapies of angiogenesis inhibitors with radiotherapy and chemotherapy are often used in clinical practice. In this article, we will review common targets against angiogenesis, the most common and up-to-date anti-angiogenic drugs and clinical treatments in recent years, including active ingredients from chemical and herbal medicines.

Mechanistic insights into the development of severe fetal growth restriction

Fetal growth restriction (FGR), which most commonly results from suboptimal placental function, substantially increases risks for adverse perinatal and long-term outcomes. The only "treatment" that exists is delivery, which averts stillbirth but does not improve outcomes in survivors. Furthermore, the potential long-term consequences of FGR to the fetus, including cardiometabolic disorders, predispose these individuals to developing FGR in their future pregnancies. This creates a multi-generational cascade of adverse effects stemming from a single dysfunctional placenta, and understanding the mechanisms underlying placental-mediated FGR is critically important if we are to improve outcomes and overall health. The mechanisms behind FGR remain unknown. However, placental insufficiency derived from maldevelopment of the placental vascular systems is the most common etiology. To highlight important mechanistic interactions within the placenta, we focus on placental vascular development in the setting of FGR. We delve into fetoplacental angiogenesis, a robust and ongoing process in normal pregnancies that is impaired in severe FGR. We review cellular models of FGR, with special attention to fetoplacental angiogenesis, and we highlight novel integrin-extracellular matrix interactions that regulate placental angiogenesis in severe FGR. In total, this review focuses on key developmental processes, with specific focus on the human placenta, an underexplored area of research.

VEGFA Isoforms as Pro-Angiogenic Therapeutics for Cerebrovascular Diseases

Therapeutic angiogenesis has long been considered a viable treatment for vasculature disruptions, including cerebral vasculature diseases. One widely-discussed treatment method to increase angiogenesis is vascular endothelial growth factor (VEGF) A. In animal models, treatment with VEGFA proved beneficial, resulting in increased angiogenesis, increased neuronal density, and improved outcome. However, VEGFA administration in clinical trials has thus far failed to replicate the promising results seen in animal models. The lack of beneficial effects in humans and the difficulty in medicinal translation may be due in part to administration methods and VEGFA's ability to increase vascular permeability. One solution to mitigate the side effects of VEGFA may be found in the VEGFA isoforms. VEGFA is able to produce several different isoforms through alternative splicing. Each VEGFA isoform interacts differently with both the cellular components and the VEGF receptors. Because of the different biological effects elicited, VEGFA isoforms may hold promise as a tangible potential therapeutic for cerebrovascular diseases.

The vascular endothelial growth factor (VEGF) system as a key regulator of ovarian follicle angiogenesis and growth

The vascular endothelial growth factor-A (VEGFA) system is a complex set of proteins, with multiple isoforms and receptors, including both angiogenic (VEGFxxx, VEGFR2) and antiangiogenic members (VEGFxxxb, VEGFR1 and soluble forms of VEGFR). The members of the VEGF system affect the proliferation, survival, and migration of endothelial and nonendothelial cells and are involved in the regulation of follicular angiogenesis and development. The production of VEGF by secondary follicles stimulates preantral follicular development by directly affecting follicular cells and promoting the acquisition of the follicular vasculature and downstream antrum formation. Additionally, the pattern of expression of the components of the VEGF system may provide a proangiogenic milieu capable of triggering angiogenesis and stimulating follicular cells to promote antral follicle growth, whereas, during atresia, this milieu becomes antiangiogenic and blocks follicular development.

Highly Multiplexed Spatially Resolved Proteomic and Transcriptional Profiling of the Glioblastoma Microenvironment Using Archived Formalin-Fixed Paraffin-Embedded Specimens

Glioblastoma is a heterogeneous tumor for which effective treatment options are limited and often insufficient. Few studies have examined the intratumoral transcriptional and proteomic heterogeneity of the glioblastoma microenvironment to characterize the spatial distribution of potential molecular and cellular therapeutic immunooncology targets. We applied an integrated multimodal approach comprised of NanoString GeoMx Digital Spatial Profiling, single-cell RNA-seq (scRNA-seq), and expert neuropathologic assessment to characterize archival formalin-fixed paraffin-embedded glioblastoma specimens. Clustering analysis and spatial cluster maps highlighted the intratumoral heterogeneity of each specimen. Mixed cell deconvolution analysis revealed that neoplastic and vascular cells were the prominent cell types throughout each specimen, with macrophages, oligodendrocyte precursors, neurons, astrocytes, and oligodendrocytes present in lower abundance and illustrated the regional distribution of the respective cellular enrichment scores. The spatial resolution of the actionable immunotherapeutic landscape showed that robust B7H3 gene and protein expression was broadly distributed throughout each specimen and identified STING and VISTA as potential targets. Lastly, we uncovered remarkable variability in VEGFA expression and discovered unanticipated associations between VEGFA, endothelial cell markers, hypoxia, and the expression of immunoregulatory genes, indicative of regionally distinct immunosuppressive microdomains. This work provides an early demonstration of the ability of an integrated panel-based spatial biology approach to characterize and quantify the intrinsic molecular heterogeneity of the glioblastoma microenvironment.

The VEGF/VEGFR Axis Revisited: Implications for Cancer Therapy

The vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor (VEGFR) axis is indispensable in the process of angiogenesis and has been implicated as a key driver of tumor vascularization. Consequently, several strategies that target VEGF and its cognate receptors, VEGFR-1 and VEGFR-2, have been designed to treat cancer. While therapies targeting full-length VEGF have resulted in an improvement in both overall survival and progression-free survival in various cancers, these benefits have been modest. In addition, the inhibition of VEGFRs is associated with undesirable off-target effects. Moreover, VEGF splice variants that modulate sprouting and non-sprouting angiogenesis have been identified in recent years. Cues within the tumor microenvironment determine the expression patterns of these variants. Noteworthy is that the mechanisms of action of these variants challenge the established norm of VEGF signaling. Furthermore, the aberrant expression of some of these variants has been observed in several cancers. Herein, developments in the understanding of the VEGF/VEGFR axis and the splice products of these molecules, as well as the environmental cues that regulate these variants are reviewed. Furthermore, strategies that incorporate the targeting of VEGF variants to enhance the effectiveness of antiangiogenic therapies in the clinical setting are discussed.

What Went Wrong with VEGF-A in Peripheral Arterial Disease? A Systematic Review and Biological Insights on Future Therapeutics

BACKGROUND

Of the 200 million patients worldwide affected by peripheral arterial disease (PAD), 4% will inevitably require major limb amputation. Previous systematic reviews presented a conflicting body of evidence in terms of vascular endothelial growth factor (VEGF) family member effects upon PAD natural progression. Despite that, modulation of intrinsic angiogenesis mechanisms targeting the VEGF family members still confers an attractive therapeutic target. The aim of the present study was to evaluate current evidence of VEGF modulation in the context of PAD.

METHODS

This is a systematic literature review conducted according to the PRISMA guidelines and registered under PROSPERO database [CRD42021285988]. Independent literature search was performed up to April 1, 2022, on six databases. A total of 22 eligible studies were identified [N: 3, interventional patient studies; N: 19, animal studies]. Animal studies were appraised by the SYRCLE risk of bias tool, while human participant studies were assessed by the Newcastle Ottawa scale. Overall, quality of evidence was deemed fair for both animal and human studies. Main study outcomes were percentage change of injured vessel lumen stenosis and neointimal area formation upon VEGF modulation (inhibition or activation) in comparison with control group.

FINDINGS

Nineteen animal models and three human participant studies were included in the systematic review and assessed separately. Positive modulation of VEGF-A in animal models resulted in a median decrease of 65.58% [95% CI 45.2; 71.87] in lumen stenosis [14 studies]. Furthermore, positive modulation of VEGF-A was found to reduce neointimal area proliferation by a median decrease of 63.41% [95% CI 41.6; 79.59] [14 studies]. Median end of study duration was 28 days [range: 14-84 days]. Data were insufficient to assess these outcomes with respect to VEGF-B or VEGF-C modulation. The limited number of available human studies presented inadequate outcome assessment despite their overall fair NOS grading.

INTERPRETATION

VEGF-A-positive modulation decreases lumen stenosis and neointimal hyperplasia in PAD simulation animal models. Previously identified variability among outcomes was found to strongly stem from the variability of experimental designs. Clinical applicability and safety profile of VEGF-A in the context of PAD remain to be defined by a robust and uniformly designed body of further animal model-based experiments.

Characterization of the Expression of Angiogenic Factors in Cutaneous Squamous Cell Carcinoma of Domestic Cats

Cutaneous squamous cell carcinoma (CSCC) is a common malignant skin cancer with a significant impact on health, and it is important to determine the degree of reliance of CSCC on angiogenesis for growth and metastasis. Major regulators of angiogenesis are the vascular endothelial growth factor (VEGF) family and their associated receptors. Alternative pre-mRNA splicing produces multiple isoforms of VEGF-A and PLGF with distinct biological properties. Several studies highlight the function of VEGF-A in CSCC, but there are no studies of the different isoforms of VEGF-A and PLGF for this neoplasm. We characterized the expression of three isoforms of VEGF-A, two isoforms of PLGF, and their receptors in cat CSCC biopsies compared to normal haired skin (NHS). Although our results revealed no significant changes in transcript levels of panVEGF-A or their isoforms, the mRNA levels of PLGF I and the receptors Flt-1 and KDR were downregulated in CSCC compared to NHS. Differences were observed in ligand:receptor mRNA expression ratio, with the expression of VEGF-A relative to its receptor KDR higher in CSCC, which is consistent with our hypothesis and prior human SCC studies. Immunolocalization in tissue showed increased expression of all measured factors and receptors in tumor cells compared to NHS and surrounding vasculature. We conclude that the factors measured may play a pivotal role in CSCC growth, although further studies are needed to clarify the role of angiogenic factors in feline CSCC.

Enhanced Microvasculature Formation and Patterning in iPSC–Derived Kidney Organoids Cultured in Physiological Hypoxia

Stem cell–derived kidney organoids have been shown to self-organize from induced pluripotent stem cells into most important renal structures. However, the structures remain immature in culture and contain endothelial networks with low connectivity and limited organoid invasion. Furthermore, the nephrons lose their phenotype after approximately 25 days. To become applicable for future transplantation, further maturation in vitro is essential. Since kidneys in vivo develop in hypoxia, we studied the modulation of oxygen availability in culture. We hypothesized that introducing long-term culture at physiological hypoxia, rather than the normally applied non-physiological, hyperoxic 21% O₂, could initiate angiogenesis, lead to enhanced growth factor expression and improve the endothelial patterning. We therefore cultured the kidney organoids at 7% O₂ instead of 21% O₂ for up to 25 days and evaluated nephrogenesis, growth factor expression such as VEGF-A and vascularization. Whole mount imaging revealed a homogenous morphology of the endothelial network with enhanced sprouting and interconnectivity when the kidney organoids were cultured in hypoxia. Three-dimensional vessel quantification confirmed that the hypoxic culture led to an increased average vessel length, likely due to the observed upregulation of VEGFA-189 and VEGFA-121, and downregulation of the antiangiogenic protein VEGF-A165b measured in hypoxia. This research indicates the importance of optimization of oxygen availability in organoid systems and the potential of hypoxic culture conditions in improving the vascularization of organoids.

How VEGF-A and its splice variants affect breast cancer development - clinical implications

BACKGROUND

Altered expression levels and structural variations in the vascular endothelial growth factor (VEGF) have been found to play important roles in cancer development and to be associated with the overall survival and therapy response of cancer patients. Particularly VEGF-A and its splice variants have been found to affect physiological and pathological angiogenic processes, including tumor angiogenesis, correlating with tumor progression, mostly caused by overexpression. This review focuses on the expression and impact of VEGF-A splice variants under physiologic conditions and in tumors and, in particular, the distribution and role of isoform VEGF165b in breast cancer.

CONCLUSIONS AND PERSPECTIVES

Many publications already highlighted the importance of VEGF-A and its splice variants in tumor therapy, especially in breast cancer, which are summarized in this review. Furthermore, we were able to demonstrate that cytoplasmatic VEGFA/165b expression is higher in invasive breast cancer tumor cells than in normal tissues or stroma. These examples show that the detection of VEGF splice variants can be performed also on the protein level in formalin fixed tissues. Although no quantitative conclusions can be drawn, these results may be the starting point for further studies at a quantitative level, which can be a major step towards the design of targeted antibody-based (breast) cancer therapies.

Novel engineered, membrane-tethered VEGF-A variants promote formation of filopodia, proliferation, survival, and cord or tube formation by endothelial cells via persistent VEGFR2/ERK signaling and activation of CDC42/ROCK pathways

Therapeutic angiogenesis would be clinically valuable in situations such as peripheral vascular disease in diabetic patients and tissue reperfusion following ischemia or injury, but approaches using traditional isoforms of vascular endothelial growth factor-A (VEGF) have had little success. The isoform VEGF165 is both soluble and matrix-associated, but can cause pathologic vascular changes. Freely diffusible VEGF121 is not associated with pathologic angiogenesis, but its failure to remain in the vicinity of the targeted area presents therapeutic challenges. In this study, we evaluate the cellular effects of engineered VEGF variants that tether extracellular VEGF121 to the cell membrane with the goal of activating VEGF receptor 2 (VEGFR2) in a sustained, autologous fashion in endothelial cells. When expressed by primary human retinal endothelial cells (hRECs), the engineered, membrane-tethered variants eVEGF-38 and eVEGF-53 provide a lasting VEGF signal that induces cell proliferation and survival, increases endothelial permeability, promotes the formation of a cord/tube network, and stimulates the formation of elongated filopodia on the endothelial cells. The engineered VEGF variants activate VEGFR2, MAPK/ERK, and the Rho GTPase mediators CDC42 and ROCK, activities that are required for the formation of the elongated filopodia. The sustained, pro-angiogenic activities induced by eVEGF-38 and eVEGF-53 support the potential of engineered VEGF variants-overexpressing endothelial cells as a novel combination of gene and cell-based therapeutic strategy for stimulating endothelial cell-autologous therapeutic angiogenesis.

Alternative Splicing: A Key Mediator of Diabetic Vasculopathy

Cardiovascular disease is the leading cause of death amongst diabetic individuals. Atherosclerosis is the prominent driver of diabetic vascular complications, which is triggered by the detrimental effects of hyperglycemia and oxidative stress on the vasculature. Research has extensively shown diabetes to result in the malfunction of the endothelium, the main component of blood vessels, causing severe vascular complications. The pathogenic mechanism in which diabetes induces vascular dysfunction, however, remains largely unclear. Alternative splicing of protein coding pre-mRNAs is an essential regulatory mechanism of gene expression and is accepted to be intertwined with cellular physiology. Recently, a role for alternative splicing has arisen within vascular health, with aberrant mis-splicing having a critical role in disease development, including in atherosclerosis. This review focuses on the current knowledge of alternative splicing and the roles of alternatively spliced isoforms within the vasculature, with a particular focus on disease states. Furthermore, we explore the recent elucidation of the alternatively spliced QKI gene within vascular cell physiology and the onset of diabetic vasculopathy. Potential therapeutic strategies to restore aberrant splicing are also discussed.

New insights on the role of vascular endothelial growth factor in biliary pathophysiology

The family of vascular endothelial growth factors (VEGFs) includes 5 members (VEGF-A to -D, and placenta growth factor), which regulate several critical biological processes. VEGF-A exerts a variety of biological effects through high-affinity binding to tyrosine kinase receptors (VEGFR-1, -2 and -3), co-receptors and accessory proteins. In addition to its fundamental function in angiogenesis and endothelial cell biology, VEGF/VEGFR signalling also plays a role in other cell types including epithelial cells. This review provides an overview of VEGF signalling in biliary epithelial cell biology in both normal and pathologic conditions. VEGF/VEGFR-2 signalling stimulates bile duct proliferation in an autocrine and paracrine fashion. VEGF/VEGFR-1/VEGFR-2 and angiopoietins are involved at different stages of biliary development. In certain conditions, cholangiocytes maintain the ability to secrete VEGF-A, and to express a functional VEGFR-2 receptor. For example, in polycystic liver disease, VEGF secreted by cystic cells stimulates cyst growth and vascular remodelling through a PKA/RAS/ERK/HIF1α-dependent mechanism, unveiling a new level of complexity in VEFG/VEGFR-2 regulation in epithelial cells. VEGF/VEGFR-2 signalling is also reactivated during the liver repair process. In this context, pro-angiogenic factors mediate the interactions between epithelial, mesenchymal and inflammatory cells. This process takes place during the wound healing response, however, in chronic biliary diseases, it may lead to pathological neo-angiogenesis, a condition strictly linked with fibrosis progression, the development of cirrhosis and related complications, and cholangiocarcinoma. Novel observations indicate that in cholangiocarcinoma, VEGF is a determinant of lymphangiogenesis and of the immune response to the tumour. Better insights into the role of VEGF signalling in biliary pathophysiology might help in the search for effective therapeutic strategies.