Extracellular regulation of VEGF: isoforms, proteolysis, and vascular patterning

Characterization of Naturally Occurring Bioactive Factor Mixtures for Bone Regeneration

In this study, the bone-regenerative potential of bioactive factors derived from adipose tissue, platelet-rich plasma (PRP) and conditioned medium from hypoxia-treated human telomerase immortalized bone-marrow-derived mesenchymal stem cells (hTERT-MSC) was investigated in vitro with the aim to develop cost-effective and efficient bone substitutes for optimized regeneration of bone defects. Adipose tissue was harvested from human donors undergoing reconstructive surgery, and adipose tissue extract (ATE) was prepared. Platelet lysates (PL) were produced by repeated freeze-thaw cycles of PRP, and hypoxia-conditioned medium (HCM) was obtained by culturing human telomerase immortalized bone-marrow-derived mesenchymal stromal cells for 5 days with 1% O2. Besides analysis by cytokine and angiogenesis arrays, ELISA was performed. Angiogenic potential was investigated in cocultures of bone-marrow-derived (BM)-MSC and human umbilical vein endothelial cells. Multiple angiogenic proteins and cytokines were detected in all growth factor mixtures. HCM and ATE contained high amounts of angiogenin and CCL2/MCP-1, whereas PL contained high amounts of IGFBP-1. Culturing cells with HCM and ATE significantly increased specific ALP activity of BM-MSC as well as tubule length and junctions of endothelial networks, indicating osteogenic and angiogenic stimulation. To achieve a synergism between chemoattractive potential and osteogenic and angiogenic differentiation capacity, a combination of different growth factors appears promising for potential clinical applications.

Regulation of matrix metalloproteinases 2 and 9 in corneal neovascularization

Corneal neovascularization (CNV), a pathological process of angiogenesis, can lead to serious consequences in the cornea. CNV is generally proved to associate with inflammation in the cornea closely, which is mainly elicited by the disruption of equilibrium between angiogenic and antiangiogenic factors. Angiogenic factors including vascular endothelial growth factors (VEGFs), basic fibroblast growth factors (bFGFs), and matrix metalloproteinases (MMPs) are vital factors in the formation of CNV. Especially VEGFs are convinced to be the core angiogenic factors in CNV, and MMPs are proved to exert dual effects on the process. Strikingly, matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) are determined to play key roles in the formation of CNV, while the mechanism is still vague. In this review, the latest researches are reviewed to discuss the role of MMP-2 and MMP-9 in CNV, respectively, and some inhibitors of them are presented. We hope to provide a new direction of drug research for CNV.

Role of meprin metalloproteases in metastasis and tumor microenvironment

A crucial step for tumor cell extravasation and metastasis is the migration through the extracellular matrix, which requires proteolytic activity. Hence, proteases, particularly matrix metalloproteases (MMPs), have been discussed as therapeutic targets and their inhibition should diminish tumor growth and metastasis. The metalloproteases meprin α and meprin β are highly abundant on intestinal enterocytes and their expression was associated with different stages of colorectal cancer. Due to their ability to cleave extracellular matrix (ECM) components, they were suggested as pro-tumorigenic enzymes. Additionally, both meprins were shown to have pro-inflammatory activity by cleaving cytokines and their receptors, which correlates with chronic intestinal inflammation and associated conditions. On the other hand, meprin β was identified as an essential enzyme for the detachment and renewal of the intestinal mucus, important to prevent bacterial overgrowth and infection. Considering this, it is hard to estimate whether high activity of meprins is generally detrimental or if these enzymes have also protective functions in certain cancer types. For instance, for colorectal cancer, patients with high meprin β expression in tumor tissue exhibit a better survival prognosis, which is completely different to prostate cancer. This demonstrates that the very same enzyme may have contrary effects on tumor initiation and growth, depending on its tissue and subcellular localization. Hence, precise knowledge about proteolytic enzymes is required to design the most efficient therapeutic options for cancer treatment. In this review, we summarize the current findings on meprins' functions, expression, and cancer-associated variants with possible implications for tumor progression and metastasis.

Neuropilin: Handyman and Power Broker in the Tumor Microenvironment

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

A novel LC-MS/MS approach to the pharmacokinetic study of free and bound aflibercept simultaneously

To comprehensively evaluate the pharmacokinetic (PK) characteristics of aflibercept, we established a liquid chromatography with tandem mass spectrometry (LC-MS/MS) method to determine the concentration of vascular endothelial growth factor (VEGF)-A-bound aflibercept and free aflibercept. A specific sample preparation method of nano-surface and molecular-orientation limited (nSMOL) proteolysis was performed to extract both free and bound aflibercept from plasma. The tryptic peptides unique to aflibercept and VEGF-A were selected to quantify the amounts of total aflibercept and aflibercept-VEGF complex, respectively. The method was validated by evaluating its selectivity, linearity, precision, accuracy, extraction recovery, matrix effect, and stability. It was then successfully used to quantify total and bound aflibercept concentrations in cynomolgus monkey plasma, while indirectly obtaining the concentration of free aflibercept by subtraction. The PK results of this LC-MS/MS method are comparable to the traditional enzyme-linked immunosorbent assay (ELISA) results. It is thus a reliable and complementary method for the PK evaluation of aflibercept. Graphical abstract.

New Aspects of Ultrasound-Mediated Targeted Delivery and Therapy for Cancer

Ultrasound-mediated targeted delivery (UMTD), a novel delivery modality of therapeutic materials based on ultrasound, shows great potential in biomedical applications. By coupling ultrasound contrast agents with therapeutic materials, UMTD combines the advantages of ultrasound imaging and carrier, which benefit deep tissue penetration and high concentration aggregation. In this paper we introduced recent advances in ultrasound contrast agents and applications in tumor therapy. Ultrasound contrast agents were categorized by their functions, mainly including thermosensitive, pH-sensitive and photosensitive ultrasound contrast agents. The various applications of UMTD in tumor treatment were summarized as follows: drug therapy, transfection of anti-oncogene, RNA interference, vaccine immunotherapy, monoclonal antibody immunotherapy, adoptive cellular immunotherapy, cytokine immunotherapy, and so on. In the end, we elaborated on the current challenges and provided perspectives of UMTD for clinical applications.

Triple-marker cardiac MRI detects sequential tissue changes of healing myocardium after a hydrogel-based therapy

Regenerative therapies based on injectable biomaterials, hold an unparalleled potential for treating myocardial ischemia. Yet, noninvasive evaluation of their efficacy has been lagging behind. Here, we report the development and longitudinal application of multiparametric cardiac magnetic resonance imaging (MRI) to evaluate a hydrogel-based cardiac regenerative therapy. A pH-switchable hydrogel was loaded with slow releasing insulin growth factor 1 and vascular endothelial growth factor, followed by intramyocardial injection in a mouse model of ischemia reperfusion injury. Longitudinal cardiac MRI assessed three hallmarks of cardiac regeneration: angiogenesis, resolution of fibrosis and (re)muscularization after infarction. The multiparametric approach contained dynamic contrast enhanced MRI that measured improved vessel features by assessing fractional blood volume and permeability*surface area product, T1-mapping that displayed reduced fibrosis, and tagging MRI that showed improved regional myocardial strain in hydrogel treated infarcts. Finally, standard volumetric MRI demonstrated improved left ventricular functioning in hydrogel treated mice followed over time. Histology confirmed MR-based vessel features and fibrotic measurements. Our novel triple-marker strategy enabled detection of ameliorated regeneration in hydrogel treated hearts highlighting the translational potential of these longitudinal MRI approaches.

Associations of microRNAs, Angiogenesis-Regulating Factors and CFH Y402H Polymorphism-An Attempt to Search for Systemic Biomarkers in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) remains the leading cause of blindness in elderly people, but the pathophysiology of this disease is still largely unknown. We investigated the systemic expression of angiogenesis-regulating growth factors and selected miRNAs known to regulate angiogenesis in AMD patients. We also focused on possible correlations of their expression with the presence of CFH Y402H or ARMS A69S risk variants. A total of 354 AMD patients and 121 controls were enrolled in this study. The levels of angiogenesis-regulating factors were analyzed in plasma samples using Luminex technology. The expression of selected miRNAs was analyzed in peripheral blood plasma using real-time qPCR. The genetic analysis was performed with an Illumina NextSeq500 system. AMD was an independent factor associated with lower levels of angiogenin (β = −0.29, p < 0.001), endostatin (β = −0.18, p < 0.001), FGF-basic (β = −0.18, p < 0.001), PlGF (β = −0.24, p < 0.001), miRNA-21-3p (β = −0.13, p = 0.01) and miRNA-155-5p (β = −0.16, p = 0.002); and with higher levels of FGF-acidic (β = 0.11, p = 0.03), miRNA-23a-3p (β = 0.17, p < 0.001), miRNA-126-5p (β = 0.13, p = 0.009), miRNA-16-5p (β = 0.40, p < 0.001), miRNA-17-3p (β = 0.13, p = 0.01), miRNA-17-5p (β = 0.17, p < 0.001), miRNA-223-3p (β = 0.15, p = 0.004), and miRNA-93 (β = 0.11, p = 0.04). The expression of analyzed miRNA molecules significantly correlated with the levels of tested angiogenesis-regulating factors and clinical parameters in AMD patients, whereas such correlations were not observed in controls. We also found an association between the CFH Y402H polymorphism and miRNA profiles, whereby TT homozygotes showed evidently higher expression of miRNA-16-5p than CC homozygotes or TC heterozygotes (p = 0.0007). Our results suggest that the balance between systemic pro- and anti-angiogenic factors and miRNAs is vital in multifactorial AMD pathogenesis.

VEGF-A-Cleavage by FSAP and Inhibition of Neo-Vascularization

Alternative splicing leads to the secretion of multiple forms of vascular endothelial growth factor-A (VEGF-A) that differ in their activity profiles with respect to neovascularization. FSAP (factor VII activating protease) is the zymogen form of a plasma protease that is activated (FSAPa) upon tissue injury via the release of histones. The purpose of the study was to determine if FSAPa regulates VEGF-A activity in vitro and in vivo. FSAP bound to VEGF₁₆₅, but not VEGF₁₂₁, and VEGF₁₆₅ was cleaved in its neuropilin/proteoglycan binding domain. VEGF₁₆₅ cleavage did not alter its binding to VEGF receptors but diminished its binding to neuropilin. The stimulatory effects of VEGF₁₆₅ on endothelial cell proliferation, migration, and signal transduction were not altered by FSAP. Similarly, proliferation of VEGF receptor-expressing BAF3 cells, in response to VEGF₁₆₅, was not modulated by FSAP. In the mouse matrigel model of angiogenesis, FSAP decreased the ability of VEGF₁₆₅, basic fibroblast growth factor (bFGF), and their combination, to induce neovascularization. Lack of endogenous FSAP in mice did not influence neovascularization. Thus, FSAP inhibited VEGF₁₆₅-mediated angiogenesis in the matrigel model in vivo, where VEGF’s interaction with the matrix and its diffusion are important.

TRF2 positively regulates SULF2 expression increasing VEGF-A release and activity in tumor microenvironment

The telomeric protein TRF2 is overexpressed in several human malignancies and contributes to tumorigenesis even though the molecular mechanism is not completely understood. By using a high-throughput approach based on the multiplexed Luminex X-MAP technology, we demonstrated that TRF2 dramatically affects VEGF-A level in the secretome of cancer cells, promoting endothelial cell-differentiation and angiogenesis. The pro-angiogenic effect of TRF2 is independent from its role in telomere capping. Instead, TRF2 binding to a distal regulatory element promotes the expression of SULF2, an endoglucosamine-6-sulfatase that impairs the VEGF-A association to the plasma membrane by inducing post-synthetic modification of heparan sulfate proteoglycans (HSPGs). Finally, we addressed the clinical relevance of our findings showing that TRF2/SULF2 expression is a worse prognostic biomarker in colorectal cancer (CRC) patients.

Bioassay for Endothelial Damage Mediators Retrieved by Hemoadsorption

Hemoadsorption devices are used to treat septic shock by adsorbing inflammatory cytokines and as yet incompletely defined danger and pathogen associated molecular patterns. In an ideal case, hemoadsorption results in immediate recovery of microvascular endothelial cells’ (mEC) function and rapid recovery from catecholamine-dependency and septic shock. We here tested a single device, which consists of polystyrene-divinylbenzene core particles of 450 μm diameter with a high affinity for hydrophobic compounds. The current study aimed at the proof of concept that endothelial-specific damage mediators are adsorbed and can be recovered from hemoadsorption devices. Because of excellent clinical experience, we tested protein fractions released from a hemoadsorber in a novel endothelial bioassay. Video-based, long-term imaging of mEC proliferation and cell death were evaluated and combined with apoptosis and ATP measurements. Out of a total of 39 fractions recovered from column fractionation, we identified 3 fractions that caused i) inhibition of mEC proliferation, ii) increased cell death and iii) induction of apoptosis in mEC. When adding these 3 fractions to mEC, their ATP contents were reduced. These fractions contained proteins of approximately 15 kDa, and high amounts of nucleic acid, which was at least in part oxidized. The efficacy for endothelial cell damage prevention by hemoadsorption can be addressed by a novel endothelial bioassay and long-term video observation procedures. Protein fractionation of the hemoadsorption devices used is feasible to study and define endothelial damage ligands on a molecular level. The results suggest a significant effect by circulating nucleic acids – bound to an as yet undefined protein, which may constitute a major danger-associated molecular pattern (DAMP) in the exacerbation of inflammation when patients experience septic shock. Hemoadsorption devices may thus limit endothelial damage, through the binding of nucleic acid-bearing aggregates and thus contribute to improved endothelial barrier function.

Human Umbilical Tissue-Derived Cells Secrete Soluble VEGFR1 and Inhibit Choroidal Neovascularization

Exudative age-related macular degeneration (AMD), characterized by choroidal neovascularization (CNV), is the leading cause of irreversible blindness in developed countries. Anti-vascular endothelial growth factor (VEGF) drugs are the standard treatment for AMD, but they have limitations. Cell therapy is a promising approach for ocular diseases, and it is being developed in the clinic for the treatment of retinal degeneration, including AMD. We previously showed that subretinal injection of human umbilical tissue-derived cells (hUTCs) in a rodent model of retinal degeneration preserved photoreceptors and visual function through rescue of retinal pigment epithelial (RPE) cell phagocytosis. Here we investigated the effect of hUTCs on a rat model of laser-induced CNV and on a human RPE cell line, ARPE-19, for VEGF production. We demonstrate that subretinal injection of hUTCs significantly inhibited CNV and lowered choroidal VEGF in vivo. VEGF release from ARPE-19 decreased when co-cultured with hUTCs. Soluble VEGF receptor 1 (sVEGFR1) is identified as the only factor in hUTC conditioned medium (CM) that binds to VEGF. The level of exogenous recombinant VEGF in hUTC CM was dramatically reduced and could be recovered with sVEGFR1-neutralizing antibody. This suggests that hUTC inhibits angiogenesis through the secretion of sVEGFR1 and could serve as a novel treatment for angiogenic ocular diseases, including AMD.

Heparan Sulfate-Editing Extracellular Sulfatases Enhance VEGF Bioavailability for Ischemic Heart Repair

RATIONALE

Mechanistic insight into the inflammatory response after acute myocardial infarction may inform new molecularly targeted treatment strategies to prevent chronic heart failure.

OBJECTIVE

We identified the sulfatase SULF2 in an in silico secretome analysis in bone marrow cells from patients with acute myocardial infarction and detected increased sulfatase activity in myocardial autopsy samples. SULF2 (Sulf2 in mice) and its isoform SULF1 (Sulf1) act as endosulfatases removing 6-O-sulfate groups from heparan sulfate (HS) in the extracellular space, thus eliminating docking sites for HS-binding proteins. We hypothesized that the Sulfs have a role in tissue repair after myocardial infarction.

METHODS AND RESULTS

Both Sulfs were dynamically upregulated after coronary artery ligation in mice, attaining peak expression and activity levels during the first week after injury. Sulf2 was expressed by monocytes and macrophages, Sulf1 by endothelial cells and fibroblasts. Infarct border zone capillarization was impaired, scar size increased, and cardiac dysfunction more pronounced in mice with a genetic deletion of either Sulf1 or Sulf2. Studies in bone marrow-chimeric Sulf-deficient mice and Sulf-deficient cardiac endothelial cells established that inflammatory cell-derived Sulf2 and endothelial cell-autonomous Sulf1 promote angiogenesis. Mechanistically, both Sulfs reduced HS sulfation in the infarcted myocardium, thereby diminishing Vegfa (vascular endothelial growth factor A) interaction with HS. Along this line, both Sulfs rendered infarcted mouse heart explants responsive to the angiogenic effects of HS-binding Vegfa₁₆₄ but did not modulate the angiogenic effects of non-HS-binding Vegfa₁₂₀. Treating wild-type mice systemically with the small molecule HS-antagonist surfen (bis-2-methyl-4-amino-quinolyl-6-carbamide, 1 mg/kg/day) for 7 days after myocardial infarction released Vegfa from HS, enhanced infarct border-zone capillarization, and exerted sustained beneficial effects on cardiac function and survival.

CONCLUSIONS

These findings establish HS-editing Sulfs as critical inducers of postinfarction angiogenesis and identify HS sulfation as a therapeutic target for ischemic tissue repair.

Immunotherapy: breaching the barriers for cancer treatment

The great ambition to treat cancer through harnessing a patient's own immune responses has started to become reality. Clinical trials have shown impressive results and some patients reaching the end of existing treatment options have achieved full remission. Yet the response rate even within the most promising trials remain at just 30-40% of patients. To date, the focus of immunotherapy research has been to identify tumour antigens, and to enhance activation of effector lymphocytes. Yet this is only the first step to effective immunotherapy for a broader range of patients. Activated cytotoxic T cells can only act on their tumour cell targets if they have free and easy access to all tumour regions. Solid tumours are complex, heterogeneous environments which vary greatly in their physical properties. We must now focus our efforts on understanding how factors such as the composition, density and geometry of tumour extracellular matrix acts to impede or promote immune cell infiltration and activation, and work to design novel pharmacological interventions which restore and enhance leucocyte trafficking within solid tumours. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.

Peripheral blood mononuclear cells extracts VEGF protein levels and VEGF mRNA: Associations with inflammatory molecules in a healthy population

Background

Vascular endothelial growth factor (VEGF) is a signal protein, implicated in various physiological and pathophysiological processes together with other common inflammatory biomarkers. However, their associations have not yet been fully elucidated. In the present study, we investigated associations between VEGF and four specific VEGF mRNA isoforms with levels of 11 inflammation molecules, derived from peripheral blood mononuclear cells (PBMCs) extracts.

Methods

Healthy participants from the STANISLAS Family Study (n = 285) were included. Levels of VEGF (four mRNA isoforms and protein levels) and inflammatory molecules (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, INF-γ, TNF-α, MCP-1, EGF) were measured in PBMCs extracts. Multiple regression analyses were performed, adjusted for age and gender.

Results

The analyses revealed significant associations between VEGF protein levels and levels of IL-4 (β = 0.028, P = 0.013), MCP-1 (β = 0.015, P<0.0001) and EGF (β = 0.017, P<0.0001). Furthermore, mRNA isoform VEGF₁₆₅ was associated with MCP-1 and IL-1α (P = 0.002 and P = 0.008, respectively); and mRNA isoform VEGF₁₈₉ was associated with IL-4 and IL-6 (P = 0.019 and P = 0.034, respectively).

Conclusions

To our knowledge, the present study represents the first investigation that successfully demonstrates links between VEGF protein levels and inflammatory molecules levels derived from PBMCs extracts and identifies associations between specific VEGF mRNA isoforms and inflammatory molecules.

Impact

These findings provide novel insights that may assist in the development of new tissue and mRNA isoform specific measurements of VEGF levels, which may positively contribute to predicting the risk of common complex diseases and response of currently used anti-VEGF agents, and developing of novel targeted therapies for VEGF-related pathophysiology.

Promotion of angiogenesis by M13 phage and RGD peptide in vitro and in vivo

One of the most important goals of regenerative medicines is to generate alternative tissues with a developed vascular network. Endothelial cells are the most important cell type required in angiogenesis process, contributing to the blood vessels formation. The stimulation of endothelial cells to initiate angiogenesis requires appropriate extrinsic signals. The aim of this study was to evaluate the effects of M13 phage along with RGD peptide motif on in vitro and in vivo vascularization. The obtained results demonstrated the increased cellular proliferation, HUVECs migration, cells altered morphology, and cells attachment to M13 phage-RGD coated surface. In addition, the expression of Vascular Endothelial Growth Factor A (VEGF-A), VEGF Receptors 2 and 3, Matrix Metalloproteinase 9 (MMP9), and epithelial nitric oxide synthase (eNOS) transcripts were significantly upregulated due to the HUVECs culturing on M13 phage-RGD coated surface. Furthermore, VEGF protein secretion, nitric oxide, and reactive oxygen species (ROS) production were significantly increased in cells cultured on M13 phage-RGD coated surface.

Vascular endothelial growth factor A/Vascular endothelial growth factor receptor 2 axis promotes human dental pulp stem cell migration via the FAK/PI3K/Akt and p38 MAPK signalling pathways

AIM

To investigate the effects of vascular endothelial growth factor A (VEGFA) and the underlying molecular mechanisms on the migration of human dental pulp stem cells (hDPSCs).

METHODOLOGY

The expression of VEGFA in inflammatory pulp tissue and lipopolysaccharide (LPS)-stimulated dental pulp cells was examined by immunofluorescence staining and qRT-PCR. The migration of hDPSCs was detected using transwell migration and wound healing assays. The activation of FAK, PI3K, Akt and p38 signalling was evaluated by Western blot analysis. Silence RNA (siRNA) technology was utilized to knockdown the expression of VEGFR1 (Flt-1) and VEGFR2 (Flk-1/KDR). PF573228 (inhibitor of FAK), LY294002 (inhibitor of PI3K), SB203580 (inhibitor of p38) and SU5416 (inhibitor of VEGFR2) were employed to investigate the effect of VEGFA on the migratory mechanism of hDPSCs. Data were analysed statistically using the Student's t-test or one-way ANOVA.

RESULTS

The expression levels of VEGFA in inflammatory pulp tissue in vivo and LPS-stimulated dental pulp cells in vitro were significantly greater than those in the control groups (P < 0.05). Vascular endothelial growth factor A promoted the migration of hDPSCs in a concentration-dependent manner. Several signalling pathways, including FAK, PI3K, Akt and p38, were activated by VEGFA in a dose- and time-dependent manner in hDPSCs. The VEGFA-induced migration of hDPSCs was significantly inhibited with drug inhibitors such as PF573228, LY294002, SB203580 or SU5416 (P < 0.05). These signalling pathways activated by VEGFA stimulation were significantly suppressed by pre-treatment with inhibitor of VEGFR2 (SU5416) or transfection with siRNA of VRGFR2 (P < 0.05) but not VEGFR1 siRNA.

CONCLUSIONS

Vascular endothelial growth factor A/VEGFR2 axis promoted the migration of hDPSCs via the FAK/PI3K/Akt and p38 MAPK signalling pathways. These findings reveal a novel molecular mechanism for cell migration of hDPSCs, which may contribute to the remodelling of pulp tissue and dentine.

Comparison of the ligand-binding properties of fluorescent VEGF-A isoforms to VEGF receptor 2 in living cells and membrane preparations using NanoBRET

Background and Purpose

Vascular endothelial growth factor A (VEGF‐A) is a key mediator of angiogenesis. A striking feature of the binding of a fluorescent analogue of VEGF₁₆₅a to nanoluciferase‐tagged VEGF receptor 2 (VEGFR2) in living cells is that the BRET signal is not sustained and declines over time. This may be secondary to receptor internalisation. Here, we have compared the binding of three fluorescent VEGF‐A isoforms to VEGFR2 in cells and isolated membrane preparations.

Experimental Approach

Ligand‐binding kinetics were monitored in both intact HEK293T cells and membranes (expressing nanoluciferase‐tagged VEGFR2) using BRET between tagged receptor and fluorescent analogues of VEGF₁₆₅a, VEGF₁₆₅b, and VEGF₁₂₁a. VEGFR2 endocytosis in intact cells expressing VEGFR2 was monitored by following the appearance of fluorescent ligand‐associated receptors in intracellular endosomes using automated quantitative imaging.

Key Results

Quantitative analysis of the effect of fluorescent VEGF‐A isoforms on VEGFR2 endocytosis in cells demonstrated that they produce a rapid and potent translocation of ligand‐bound VEGFR2 into intracellular endosomes. NanoBRET can be used to monitor the kinetics of the binding of fluorescent VEGF‐A isoforms to VEGFR2. In isolated membrane preparations, ligand‐binding association curves were maintained for the duration of the 90‐min experiment. Measurement of the k_off at pH 6.0 in membrane preparations indicated shorter ligand residence times than those obtained at pH 7.4.

Conclusions and Implications

These studies suggest that rapid VEGF‐A isoform‐induced receptor endocytosis shortens agonist residence times on the receptor (1/k_off) as VEGFR2 moves from the plasma membrane to the intracellular endosomes.

Anti-colorectal cancer targets of resveratrol and biological molecular mechanism: Analyses of network pharmacology, human and experimental data

In this study, colorectal cancer (CRC)-diseased targets and resveratrol (Res)-associated targets were combined and constructed by the use of grouped databases for identification of the predicted targets. After production of target-functional protein interaction network of Res anti-CRC, the topological analysis was used to create the core targets of Res anti-CRC. All core targets performed the analyses of biological function and pathway enrichment to optimize the biological processes and key signaling pathways of Res anti-CRC. The resultant five core therapeutic targets of Res anti-CRC were identified as protein kinase B1 (AKT1), interleukin 6 (IL6), Tumor protein p53 (TP53), vascular endothelial growth factor, and mitogen-activated protein kinase 1, respectively. Biological processes of Res anti-CRC were predominantly associated with regulating apoptosis, immune response, cellular communication, signal transduction, and metabolism of the nuclide. In addition, the top 10 key signaling pathways were identified, respectively. In human CRC sample assays, CRC histologic sections showed elevated expression of AKT1 and IL6 proteins, accompanied with abnormal changes in blood molecules. In pharmacological experiments of Res anti-CRC in vitro, Res-treated HCT116 cells showed inhibited cell growth, induced cell death. In addition, downregulation of intracellular AKT1 and IL6 expression were checked in Res-treated HCT116 cells. Taken together, these bioinformatic findings and preliminary validated data uncovered pharmacological molecular mechanisms associated with Res anti-CRC, and further identified top five core therapeutic targets. Beneficially, these five predicted targets might serve as potential biomolecules for anti-CRC treatment.

The roles and role-players in thyroid cancer angiogenesis

Thyroid cancer is the most prevalent endocrine cancer worldwide. Angiogenesis, the formation of new blood vessels, plays a pivotal role in the development and progression of tumors. Over the past years, cancer research has focused on the ability of tumors to induce newly formed blood vessel, because tumor growth and the process of cancer metastasis mainly depends on angiogenesis. Tumor neovascularization occurs following the imbalance between pro-angiogenic and anti-angiogenic factors until the tumor switches to an angiogenic phenotype. A number of signaling factors and receptors that are implicated in the regulation of angiogenesis have been identified and characterized; most notably, the vascular endothelial growth factors (VEGFs) family and their receptors, which are the main pro-angiogenic molecules during early development and in pathological conditions such as cancer. Although thyroid is a highly vascularized organ, angiogenic switch in tumors of this organ leads to the formation of a vast network of blood vessels that favors the dissemination of tumor cells to distant organs and results in deterioration of patient conditions. Accordingly, the identification of key angiogenic biomarkers for thyroid cancer can facilitate diagnosis, prognosis and clinical decision-making and also may help to discover targeting factors for effective cancer therapy as well as monitoring response to therapy. Hence, the main purposes of this review are to summarize the types and mechanisms of angiogenesis emphasizing the prominent factors implicated in thyroid cancer angiogenesis.

Is it useful to use several "omics" for obtaining valuable results?

The integration of cell communication and the transfer of signals from stimuli via transcription to translation and further to activation of new protein is crucial for appropriate metabolism and function of living organisms. The overall elucidation and the examination of these complex processes require multistep laboratory approaches in order to obtain results which will not only detect particular stage but also indicate the mechanisms lying upon this process. Such results will be reliable because they will cover multidirectional methods and approaches. The analysis of currently available results already provided with the conclusion that often single omics approach does not correspond with other expected information and may bring misinterpretations. That is why the integration of several "omics" is useful for searching entire explanations and answers as well as appropriate interpretation of obtained complex results. The hypothesis was stated that "from transcriptomics can not be concluded to proteomics". This review focuses on the reasons for the integration of transcriptomic, proteomic and other-omics analysis. Moreover it also describes the examples of clinical meanings and mentions some methods used in these approaches.

The heparin binding domain of von Willebrand factor binds to growth factors and promotes angiogenesis in wound healing

During wound healing, the distribution, availability, and signaling of growth factors (GFs) are orchestrated by their binding to extracellular matrix components in the wound microenvironment. Extracellular matrix proteins have been shown to modulate angiogenesis and promote wound healing through GF binding. The hemostatic protein von Willebrand factor (VWF) released by endothelial cells (ECs) in plasma and in the subendothelial matrix has been shown to regulate angiogenesis; this function is relevant to patients in whom VWF deficiency or dysfunction is associated with vascular malformations. Here, we show that VWF deficiency in mice causes delayed wound healing accompanied by decreased angiogenesis and decreased amounts of angiogenic GFs in the wound. We show that in vitro VWF binds to several GFs, including vascular endothelial growth factor-A (VEGF-A) isoforms and platelet-derived growth factor-BB (PDGF-BB), mainly through the heparin-binding domain (HBD) within the VWF A1 domain. VWF also binds to VEGF-A and fibroblast growth factor-2 (FGF-2) in human plasma and colocalizes with VEGF-A in ECs. Incorporation of the VWF A1 HBD into fibrin matrices enables sequestration and slow release of incorporated GFs. In vivo, VWF A1 HBD-functionalized fibrin matrices increased angiogenesis and GF retention in VWF-deficient mice. Treatment of chronic skin wounds in diabetic mice with VEGF-A165 and PDGF-BB incorporated within VWF A1 HBD-functionalized fibrin matrices accelerated wound healing, with increased angiogenesis and smooth muscle cell proliferation. Therefore, the VWF A1 HBD can function as a GF reservoir, leading to effective angiogenesis and tissue regeneration.

Angioneurins - Key regulators of blood-brain barrier integrity during hypoxic and ischemic brain injury

The loss of blood-brain barrier (BBB) integrity leading to vasogenic edema and brain swelling is a common feature of hypoxic/ischemic brain diseases such as stroke, but is also central to the etiology of other CNS disorders. In the past decades, numerous proteins, belonging to the family of angioneurins, have gained increasing attention as potential therapeutic targets for ischemic stroke, but also other CNS diseases attributed to BBB dysfunction. Angioneurins encompass mediators that affect both neuronal and vascular function. Recently, increasing evidence has been accumulated that certain angioneurins critically determine disease progression and outcome in stroke among others through multifaceted effects on the compromised BBB. Here, we will give a concise overview about the family of angioneurins. We further describe the most important cellular and molecular components that contribute to structural integrity and low permeability of the BBB under steady-state conditions. We then discuss BBB alterations in ischemic stroke, and highlight underlying cellular and molecular mechanisms. For the most prominent angioneurin family members including vascular endothelial growth factors, angiopoietins, platelet-derived growth factors and erythropoietin, we will summarize current scientific literature from experimental studies in animal models, and if available from clinical trials, on the following points: (i) spatiotemporal expression of these factors in the healthy and hypoxic/ischemic CNS, (ii) impact of loss- or gain-of-function during cerebral hypoxia/ischemia for BBB integrity and beyond, and (iii) potential underlying molecular mechanisms. Moreover, we will highlight novel therapeutic strategies based on the activation of endogenous angioneurins that might improve BBB dysfuntion during ischemic stroke.

Context-dependent regulation of receptor tyrosine kinases: Insights from systems biology approaches

Receptor tyrosine kinases (RTKs) are cell membrane proteins that provide cells with the ability to sense proteins in their environments. Many RTKs are essential to development and organ growth. Derangement of RTKs-by mutation or by overexpression-is central to several developmental and adult disorders including cancer, short stature, and vascular pathologies. The mechanism of action of RTKs is complex and is regulated by contextual components, including the existence of multiple competing ligands and receptors in many families, the intracellular location of the RTK, the dynamic and cell-specific coexpression of other RTKs, and the commonality of downstream signaling pathways. This means that both the state of the cell and the microenvironment outside the cell play a role, which makes sense given the pivotal location of RTKs as the nexus linking the extracellular milieu to intracellular signaling and modification of cell behavior. In this review, we describe these different contextual components through the lens of systems biology, in which both computational modeling and experimental "omics" approaches have been used to better understand RTK networks. The complexity of these networks is such that using these systems biology approaches is necessary to get a handle on the mechanisms of pathology and the design of therapeutics targeting RTKs. In particular, we describe in detail three concrete examples (involving ErbB3, VEGFR2, and AXL) that illustrate how systems approaches can reveal key mechanistic and therapeutic insights. This article is categorized under: Biological Mechanisms > Cell Signaling Models of Systems Properties and Processes > Mechanistic Models Translational, Genomic, and Systems Medicine > Therapeutic Methods.

TAZ Expression on Endothelial Cells Is Closely Related to Blood Vascular Density and VEGFR2 Expression in Astrocytomas

Significant angiogenesis is one of the malignant features in astrocytomas. Cotransfactor Yes-associated protein/transcriptional coactivator with PDZ-binding motif (YAP/TAZ) is a major regulator of embryonic angiogenesis, in which it plays an essential role in vascular tip cell migration, blood vessel formation, and vascular barrier maturation. We quantified TAZ expression on blood vessels and parenchyma of astrocytomas of varying malignancy to investigate its role in tumor angiogenesis. Replicating others' findings, we observed that TAZ is expressed in tumor cells but also in vascular cells. TAZ expression in both cell types was correlated with malignant grade. Immunofluorescence staining for TAZ, smooth muscle actin, and CD31 verified that TAZ-expressing vascular cells are endothelial cells, not pericytes. Analysis of blood vessel density using CD31 immunolabeling revealed that endothelial cell TAZ immunoreactivity was positively correlated with blood vessel density. MRI-acquired tumor blood perfusion measurements in 12 pre-excision glioblastomas and subsequent postexcision TAZ staining supported that TAZ immunoreactivity-blood vessel density correlation with blood perfusion. In glioblastoma, TAZ staining was denser in glomerular neovascularization than that in the thin-walled neovascularization. TAZ expression was also correlated with vascular endothelial growth factor 2 (VEGFR2) immunoreactivity on endothelial cells. Our results indicate that VEGFR2/TAZ signaling pathway plays an important role in angiogenesis in astrocytomas.

Neuropilins in the Context of Tumor Vasculature

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

Identifying the Growth Factors for Improving Neointestinal Regeneration in Rats through Transcriptome Analysis Using RNA-Seq Data

Using our novel surgical model of simultaneous intestinal adaptation "A" and neointestinal regeneration "N" conditions in individual rats to determine feasibility for research and clinical application, we further utilized next generation RNA sequencing (RNA-Seq) here in normal control tissue and both conditions ("A" and "N") across time to decipher transcriptome changes in neoregeneration and adaptation of intestinal tissue at weeks 1, 4, and 12. We also performed bioinformatics analyses to identify key growth factors for improving intestinal adaptation and neointestinal regeneration. Our analyses indicate several interesting phenomena. First, Gene Ontology and pathway analyses indicate that cell cycle and DNA replication processes are enhanced in week 1 "A"; however, in week 1 "N", many immune-related processes are involved. Second, we found some growth factors upregulated or downregulated especially in week 1 "N" versus "A". Third, based on each condition and time point versus normal control tissue, we found in week 1 "N" BMP2, BMP3, and NTF3 are significantly and specifically downregulated, indicating that the regenerative process may be inhibited in the absence of these growth factors. This study reveals complex growth factor regulation in small neointestinal regeneration and intestinal adaptation and provides potential applications in tissue engineering by introducing key growth factors identified here into the injury site.

Role of the complement system in the tumor microenvironment

The complement system has traditionally been considered a component of innate immunity against invading pathogens and "nonself" cells. Recent studies have demonstrated the immunoregulatory functions of complement activation in the tumor microenvironment (TME). The TME plays crucial roles in tumorigenesis, progression, metastasis and recurrence. Imbalanced complement activation and the deposition of complement proteins have been demonstrated in many types of tumors. Plasma proteins, receptors, and regulators of complement activation regulate several biological functions of stromal cells in the TME and promote the malignant biological properties of tumors. Interactions between the complement system and cancer cells contribute to the proliferation, epithelial-mesenchymal transition, migration and invasion of tumor cells. In this review, we summarize recent advances related to the function of the complement system in the TME and discuss the therapeutic potential of targeting complement-mediated immunoregulation in cancer immunotherapy.

Targeting the vasculature of tumours: combining VEGF pathway inhibitors with radiotherapy

The development of blood vessels by the process of angiogenesis underpins the growth and metastasis of many tumour types. Various angiogenesis inhibitors targeted against vascular endothelial growth factor A (VEGF-A) and its receptors have entered the clinic more than a decade ago. However, despite substantial clinical improvements, their overall efficacy proved to be significantly lower than many of the pre-clinical studies had predicted. Antiangiogenic agents have been combined with chemotherapy, radiotherapy and more recently immunotherapy in many pre-clinical and clinical studies in an effort to improve their efficacy. To date, only their use alongside chemotherapy is approved as part of standard treatment protocols. Most pre-clinical studies have reported improved tumour control from the addition of antiangiogenic therapies to radiotherapy and progress has been made in unravelling the complex mechanisms through which VEGF inhibition potentiates radiotherapy responses. However, the efficacy of this combination is variable, and many questions still remain as to how best to administer the two modalities to achieve optimal response and minimal toxicity. One important limiting factor is that, unlike some other targeted therapies, antiangiogenic agents are not administered to selected patient populations, since biomarkers for identifying responders have not yet been established. Here, we outline VEGF biology and review current approaches that aim to identify biomarkers for stratifying patients for treatment with angiogenesis inhibitors. We also discuss current progress in elucidating mechanisms of interaction between radiotherapy and VEGF inhibitors. Ongoing clinical trials will determine whether these combinations will ultimately improve treatment outcomes for cancer patients.

Intestinal microcirculation and necrotizing enterocolitis: The vascular endothelial growth factor system

Necrotizing enterocolitis (NEC), a leading cause of morbidity and mortality in preterm neonates, is a devastating disease characterized by intestinal tissue inflammation and necrosis. NEC pathogenesis is multifactorial but remains unclear. Translocation of bacteria and/or bacterial products across a weak intestinal barrier in the setting of impaired mucosal immunity leads to an exaggerated inflammatory response and secondary mucosal epithelial injury. In addition to prematurity, other risk factors for NEC include congenital heart disease, maternal pre-eclampsia with placental vascular insufficiency, severe anemia and blood transfusion - all conditions that predispose the intestine to ischemia. We recently found that maldevelopment of the intestinal microvasculature plays an important role in NEC pathogenesis. Here we review the evidence supporting a role for defective development of the intestinal mucosal microvasculature and perturbations of intestinal blood flow in NEC, emphasizing the importance of vascular endothelial growth factor (VEGF) and the VEGF receptor-2 signaling pathway.

Plasminogen/thrombomodulin signaling enhances VEGF expression to promote cutaneous wound healing

Plasminogen (Plg) and thrombomodulin (TM) are glycoproteins well known for fibrinolytic and anticoagulant functions, respectively. Both Plg and TM are essential for wound healing. However, their significance during the reparative process was separately demonstrated in previous studies. Here, we investigate the interaction between Plg and epithelial TM and its effect on wound healing. Characterization of the wound margin revealed that Plg and TM were simultaneously upregulated at the early stage of wound healing and the two molecules were bound together. In vitro, TM silencing or knockout in keratinocytes inhibited Plg activation. Plg treatment enhanced keratinocyte proliferation and migration, and these actions were abolished by TM antibody. Keratinocyte-expressed vascular endothelial growth factor (VEGF), which presented a dose-response relationship with Plg treatment, can be suppressed by TM silencing. Moreover, treatment with VEGF antibody inhibited Plg-enhanced keratinocyte proliferation and wound recovery. In vivo, TM antibody treatment and keratinocyte-specific TM knockout can impede Plg-enhanced wound healing in mice. In high-glucose environments, Plg-enhanced VEGF expression and wound healing were suppressed due at least in part to downregulation of keratinocyte-expressed TM. Taken together, our findings suggest that activation of Plg/TM signaling may hold therapeutic potential for chronic wounds in diabetic or non-diabetic individuals. KEY MESSAGES: Plg binds to TM in cutaneous wound healing. TM facilitates the activation of Plg to Plm in keratinocytes. Epithelial TM regulates Plg-enhanced wound healing through VEGF expression.

Beyond endothelial cells: Vascular endothelial growth factors in heart, vascular anomalies and placenta

Vascular endothelial growth factors regulate vascular and lymphatic growth. Dysregulation of VEGF signaling is connected to many pathological states, including hemangiomas, arteriovenous malformations and placental abnormalities. In heart, VEGF gene transfer induces myocardial angiogenesis. Besides vascular and lymphatic endothelial cells, VEGFs affect multiple other cell types. Understanding VEGF biology and its paracrine signaling properties will offer new targets for novel treatments of several diseases.

Pentraxin 3 level is elevated in hereditary hemorrhagic telangiectasia and reflects the severity of disease-associated epistaxis

OBJECTIVES/HYPOTHESIS

We aimed to investigate if vascular endothelial growth factor (VEGF) and other angiogenic and inflammatory factors correlated with the clinical presentation in hereditary hemorrhagic telangiectasia (HHT) patients, particularly in regard to the severity of epistaxis.

STUDY DESIGN

Prospective, comparative, single-center study.

METHODS

One hundred nine samples were collected from 75 HHT patients attending the ear, nose, and throat department at Oslo University Hospital from February 2012 to August 2013. For comparison, samples were collected from 16 healthy controls. Angiogenic and inflammatory factors related to endothelial cell activation were analyzed by enzyme immunoassays. The grade of epistaxis was evaluated using the Epistaxis Severity Score and epistaxis Intensity, Frequency, and Need for Blood Transfusion score at the day of blood sampling. The presence of internal organ manifestations in the HHT group was recorded.

RESULTS

Pentraxin 3 (PTX3) was the only factor that was significantly higher in the HHT patients than the controls and showed significant correlation to the epistaxis severity grade and the hemoglobin level. The VEGF level was higher in the HHT patients compared to controls but not to a significant degree. In addition, a significant correlation of the level of VEGF and the grade of epistaxis could not be observed. Also, no significant correlations were observed between the presence of internal organ manifestations and the level of angiogenic factors.

CONCLUSIONS

PTX3, at least partly reflecting vascular inflammation, can be a potential biomarker for the severity of HHT associated epistaxis. The serum level of VEGF was not correlated with the severity of epistaxis in the HHT patients.

LEVEL OF EVIDENCE

2 Laryngoscope, 129:E44-E49, 2019.

Effects of locally applied adipose tissue-derived microvascular fragments by thermoresponsive hydrogel on bone healing

Insufficient vascularization is a major cause for the development of non-unions. To overcome this problem, adipose tissue-derived microvascular fragments (MVF) may serve as vascularization units. However, their application into bone defects needs a carrier system. Herein, we analyzed whether this is achieved by a thermoresponsive hydrogel (TRH). MVF were isolated from CD-1 mice and cultivated after incorporation into TRH, while non-incorporated MVF served as controls. Viability of MVF was assessed immunohistochemically over a 7-day period. Moreover, osteotomies were induced in femurs of CD-1 mice. The osteotomy gaps were filled with MVF-loaded TRH (TRH + MVF), unloaded TRH (TRH) or no material (control). Bone healing was evaluated 14 and 35 days postoperatively. MVF incorporated into TRH exhibited less apoptotic cells and showed a stable vessel morphology compared to controls. Micro-computed tomography revealed a reduced bone volume in TRH + MVF femurs. Histomorphometry showed less bone and more fibrous tissue after 35 days in TRH + MVF femurs compared to controls. Accordingly, TRH + MVF femurs exhibited a lower osseous bridging score and a reduced bending stiffness. Histology and Western blot analysis revealed an increased vascularization and CD31 expression, whereas vascular endothelial growth factor (VEGF) expression was reduced in TRH + MVF femurs. Furthermore, the callus of TRH + MVF femurs showed increased receptor activator of NF-κB ligand expression and higher numbers of osteoclasts. These findings indicate that TRH is an appropriate carrier system for MVF. Application of TRH + MVF increases the vascularization of bone defects. However, this impairs bone healing, most likely due to lower VEGF expression during the early course of bone healing.

STATEMENT OF SIGNIFICANCE

In the present study we analyzed for the first time the in vivo performance of a thermoresponsive hydrogel (TRH) as a delivery system for bioactive microvascular fragments (MVF). We found that TRH represents an appropriate carrier for MVF as vascularization units and maintains their viability. Application of MVF-loaded TRH impaired bone formation in an established murine model of bone healing, although vascularization was improved. This unexpected outcome was most likely due to a reduced VEGF expression in the early phase bone healing.

Computational modeling of synergistic interaction between αVβ3 integrin and VEGFR2 in endothelial cells: Implications for the mechanism of action of angiogenesis-modulating integrin-binding peptides

Cooperation between VEGFR2 and integrin αVβ3 is critical for neovascularization in wound healing, cardiovascular ischemic diseases, ocular diseases, and tumor angiogenesis. In the present study, we developed a rule-based computational model to investigate the potential mechanism by which the Src-induced integrin association with VEGFR2 enhances VEGFR2 activation. Simulations demonstrated that the main function of integrin is to reduce the degradation of VEGFR2 and hence stabilize the activation signal. In addition, receptor synthesis rate and recruitment from internal compartment were found to be sensitive determinants of the activation state of VEGFR2. The model was then applied to simulate the effect of integrin-binding peptides such as tumstatin and cilengitide on VEGFR2 signaling. Further, computational modeling proposed potential molecular mechanisms for the angiogenesis-modulating activity of other integrin-binding peptides. The model highlights the complexity of the crosstalk between αVβ3 integrin and VEGFR2 and the necessity of utilizing models to elucidate potential mechanisms in angiogenesis-modulating peptide therapy.

Angiogenesis and vasculogenic mimicry are inhibited by 8-Br-cAMP through activation of the cAMP/PKA pathway in colorectal cancer

Introduction

Vasculogenic mimicry (VM) describes the formation of an epithelial-independent tumor microcirculation system that differs from traditional angiogenesis. Angiogenesis and the formation of VM are closely related through the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway and the epithelial–mesenchymal transition (EMT) process.

Materials and methods

In this study, 8-Br-cAMP, a cAMP analog and PKA activator, was used to activate the cAMP/PKA pathway to evaluate the effects of cAMP/PKA on angiogenesis and VM in colorectal cancer (CRC) cells. We used a syngeneic model of CRC in BALB/c mice.

Results

We discovered that treatment with 8-Br-cAMP significantly reduced tumor number compared to control mice after the 7th, 14th, and 28th days of treatment. VM was evaluated by periodic acid–schiff (PAS)–CD31 staining, and we found that VM was inhibited by 8-Br-cAMP treatment in vivo. Immunohistochemistry confirmed the inhibition of vascular endothelial growth factor (VEGF) and cAMP and the activation of PKA by 8-Br-cAMP; quantitative real-time-PCR (qRT-PCR) demonstrated that 8-Br-cAMP regulated the expression of vascular endothelial (VE)-cadherin, matrix metalloproteinase 2 (MMP2), ephrin type-A receptor 2 (EphA2), and VEGF in vivo. Experiments in vitro revealed that treatment with 8-Br-cAMP and U0126 decreased VEGF expression through PKA–ERK in CT26 cells by qRT-PCR. We further confirmed that tube formation of human umbilical vein endothelial cells was inhibited by 8-Br-cAMP in vitro.

Discussion

This study demonstrates that angiogenesis and VM are inhibited by 8-Br-cAMP treatment. Our data indicate that 8-Br-cAMP acts through the cAMP/PKA–ERK pathway and through EMT processes in CRC. These findings provide an insight into mechanisms of CRC and suggest that the cAMP/PKA–ERK pathway is a novel potential therapeutic target for the treatment of CRC.

Laminin α1 orchestrates VEGFA functions in the ecosystem of colorectal carcinoma

BACKGROUND INFORMATION

Tumor stroma remodeling is a key feature of malignant tumors and can promote cancer progression. Laminins are major constituents of basement membranes that physically separate the epithelium from the underlying stroma.

RESULTS

By employing mouse models expressing high and low levels of the laminin α1 chain (LMα1), we highlighted its implication in a tumor-stroma crosstalk, thus leading to increased colon tumor incidence, angiogenesis and tumor growth. The underlying mechanism involves attraction of carcinoma-associated fibroblasts by LMα1, VEGFA expression triggered by the complex integrin α2β1-CXCR4 and binding of VEGFA to LM-111, which in turn promotes angiogenesis, tumor cell survival and proliferation. A gene signature comprising LAMA1, ITGB1, ITGA2, CXCR4 and VEGFA has negative predictive value in colon cancer.

CONCLUSIONS

Together, we have identified VEGFA, CXCR4 and α2β1 integrin downstream of LMα1 in colon cancer as of bad prognostic value for patient survival.

SIGNIFICANCE

This information opens novel opportunities for diagnosis and treatment of colon cancer.

The urokinase plasminogen activator system components are regulated by vascular endothelial growth factor D in bovine oviduct

SummaryThe mammalian oviduct plays a pivotal role in the success of early reproductive events. The urokinase plasminogen activator system (uPAS) is present in the bovine oviduct and is involved in extracellular matrix remodelling through plasmin generation. This system can be regulated by several members of the vascular endothelial growth factors (VEGF) and their receptors. In this study, the VEGF-D effect on the regulation of uPAS was evaluated. First, RT-polymerase chain reaction (PCR) analyses were used to evidence the expression of VEGF-D and its receptors in oviductal epithelial cells (BOEC). VEGF-D, VEGFR2 and VEGFR3 transcripts were found in ex vivo and in vitro BOEC, while only VEGFR2 mRNA was present after in vitro conditions. VEGF-D showed a regulatory effect on uPAS gene expression in a dose-dependent manner, inducing an increase in the expression of both uPA and its receptor (uPAR) at 24 h post-induction and decreases in the expression of its inhibitor (PAI-1). In addition, the regulation of cell migration induced by VEGF-D and uPA in BOEC monolayer cultures was analyzed. The wound areas of monolayer cultures incubated with VEGF-D 10 ng/ml or uPA 10 nM were modified and significant differences were found at 24 h for both stimulations. These results indicated that uPAS and VEGF-D systems can modify the arrangement of the bovine oviductal epithelium and contribute to the correct maintenance of the oviductal microenvironment.

Shift in VEGFA isoform balance towards more angiogenic variants is associated with tumor stage and differentiation of human hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common and aggressive type of malignant liver tumor. HCC progression depends significantly on its vascularization and formation of new blood vessels. Vascular endothelial growth factor A (VEGFA) is a crucial regulator of tumor vascularization and components of VEGF-induced cell signaling pathways are important targets of therapeutical drugs that demonstrated the highest efficiency in case of advanced HCC (sorafenib and regorafenib). VEGFA is expressed as a set of isoforms with different functional properties, thus VEGFA isoform expression pattern may affect tumor sensitivity to anti-angiogenic drugs. However, information about VEGFA isoforms expression in HCC is still incomplete and contradictory. The present study aims to quantitatively investigate VEGFA isoform expression aberrations in HCC tissue.

METHODS

A total of 50 pairs of HCC and non-tumor tissue samples were used to evaluate the VEGFA isoform spectrum using RT-PCR and quantitatively estimate changes in isoform expression using RT-qPCR. Correlations between these changes and tumor clinicopathological characteristics were analyzed.

RESULTS

We identified VEGFA-189, VEGFA-165, and VEGFA-121 as predominant isoforms in liver tissue. Anti-angiogenic VEGFA-xxxb variants constituted no more than 5% of all mature VEGFA transcripts detected and their expression was not changed significantly in HCC tissue. We demonstrated for the first time that the least active variant VEGFA-189 is frequently repressed in HCC (p < 0.001), while no uniform changes were detected for potent angiogenesis stimulators VEGFA-165 and VEGFA-121. Isoform balance in HCC shifts from VEGFA-189 towards VEGFA-165 or VEGFA-121 in the majority of cases (p < 0.001). Changes in fractions, but not expression levels, of VEGFA-189 (decrease) and VEGFA-121 (increase) correlated with advanced Tumor-Node-Metastasis (TNM) and Barcelona Clinic Liver Cancer (BCLC) tumor stages (p < 0.05), VEGFA-189 fraction reduction was also associated with poor tumor differentiation (p < 0.05).

DISCUSSION

A distinct shift in VEGFA isoform balance towards more pro-angiogenic variants occurs in HCC tissue and may modulate overall impact of VEGFA signaling. We suppose that the ratio between VEGFA isoforms is an important parameter governing HCC angiogenesis that may affect HCC progression and be used for optimizing the strategy of HCC therapy by predicting the response to anti-angiogenic drugs.