The role of c-Met and VEGFR2 in glioblastoma resistance to bevacizumab.

Dismal prognosis of glioblastoma (GBM) prompts for the identification of response predictors and therapeutic resistance mechanisms of current therapies. The authors investigated the impact of c-Met, HGF, VEGFR2 expression and microvessel density (MVD) in GBM patients submitted to second-line chemotherapy with bevacizumab. Immunohistochemical expression of c-Met, HGF, VEGFR2, and MVD was assessed in tumor specimens of GBM patients treated with bevacizumab, after progression under temozolomide. Survival analysis was evaluated according to the expression of the aforementioned biomarkers. c-Met overexpression was associated with a time-to-progression (TTP) after bevacizumab of 3 months (95% CI, 1.5-4.5) compared with a TTP of 7 months (95% CI, 4.6-9.4) in patients with low or no expression of c-Met (p = 0.05). VEGFR2 expression was associated with a TTP after bevacizumab of 3 months (95% CI, 1.8-4.2) compared with a TTP of 7 months (95% CI, 5.7-8.3) in patients with no tumoral expression of VEGFR2 (p = 0.009). Concomitant c-Met/VEGFR2 overexpression was associated with worse overall survival (13 months) compared with concomitant c-Met/VEGFR2 negative expression (19 months; p = 0.025). Our data support the hypothesis that c-Met and VEGFR2 overexpression have a role in the development of glioblastoma early resistance and might predict poorer responses to anti-angiogenic therapies.

RIPK3 modulates growth factor receptor expression in endothelial cells to support angiogenesis.

Receptor-interacting protein kinase 3 (RIPK3) is a multifunctional intracellular protein that was first recognized as an important component of the necroptosis programmed cell death pathway. RIPK3 is also highly expressed in non-necroptotic murine embryonic endothelial cells (ECs) during vascular development, indicating its potential contribution to angiogenesis. To test this hypothesis, we generated mice lacking endothelial RIPK3 and found non-lethal embryonic and perinatal angiogenesis defects in multiple vascular beds. Our in vitro data indicate that RIPK3 supports angiogenesis by regulating growth factor receptor degradation in ECs. We found that RIPK3 interacted with the membrane trafficking protein myoferlin to sustain expression of vascular endothelial growth factor receptor 2 (VEGFR2) in cultured ECs following vascular endothelial growth factor A (VEGFA) stimulation. Restoration of myoferlin, which was diminished after RIPK3 knockdown, rescued decreased VEGFR2 expression and vascular sprouting in RIPK3-deficient ECs after VEGFA treatment. In addition, we found that RIPK3 modulated expression of genes involved in endothelial identity by inhibiting ERK signaling independently of growth factor receptor turnover. Altogether, our data reveal unexpected non-necroptotic roles for RIPK3 in ECs and evidence that RIPK3 promotes developmental angiogenesis in vivo.

PD-L1 and VEGFR-2 expression in synchronous metastatic renal cell carcinoma treated with targeted therapy following cytoreductive nephrectomy.

OBJECTIVES: Few studies have independently investigated the population of patients with synchronous metastatic renal cell carcinoma (smRCC). In this study, we evaluated programmed death protein-ligand 1 (PD-L1) and vascular endothelial growth factor receptor 2 (VEGFR-2) expression in primary tumor tissue of smRCC. METHODS: A total of 96 patients with smRCC who were treated with cytoreductive nephrectomy followed by targeted therapy from January 2006 to January 2013 were identified. PD-L1 and VEGFR-2 expression were evaluated by immunohistochemistry. Kaplan-Meier and Cox methods were used for analysis. RESULTS: PD-L1 and VEGFR-2 protein immunopositivity were observed in 39.6% (38 of 96) and 58.3% (56 of 96) of patients, respectively. A significant correlation was detected between VEGFR-2 and PD-L1 expression (P = 0.030). Based on PD-L1 and VEGFR-2 expression, patients with intermediate-risk disease (n = 63) were divided into 4 subgroups including patients who were PD-L1 (+) VEGFR-2 (+) (n = 21), PD-L1 (+) VEGFR-2 (-) (n = 11), PD-L1 (-) VEGFR-2 (+) (n = 15) and PD-L1 (-) VEGFR-2 (-) (n = 16). Compared to the PD-L1 (-) VEGFR-2 (+), PD-L1 (+) VEGFR-2 (+) and PD-L1 (-) VEGFR-2 (-) groups, patients in the PD-L1 (+) VEGFR-2 (-) group had shorter progression-free survival (median, 9.0 vs. 20.0, 16.0 and 15.5 months, P < 0.05) and overall survival (median, 14.0 vs. 33.0, 24.0 and 26.5 months, P < 0.05). CONCLUSIONS: Intermediate-risk smRCC patients with PD-L1-positive and VEGFR-2-negative expression who were treated with targeted therapy following cytoreductive nephrectomy had poor prognoses. We suggest that other treatments beyond sunitinib or sorafenib may be explored in this subgroup.

Interleukin-6-mediated epigenetic control of the VEGFR2 gene induces disorganized angiogenesis in human breast tumors.

Disorganized vessels in the tumor vasculature lead to impaired perfusion, resulting in reduced accessibility to immune cells and chemotherapeutic drugs. In the breast tumor-stroma interplay, paracrine factors such as interleukin-6 (IL-6) often facilitate disordered angiogenesis. We show here that epigenetic mechanisms regulate the crosstalk between IL-6 and vascular endothelial growth factor receptor 2 (VEGFR2) signaling pathways in myoepithelial (CD10+) and endothelial (CD31+, CD105+, CD146+, and CD133-) cells isolated from malignant and nonmalignant tissues of clinically characterized human breast tumors. Tumor endothelial (Endo-T) cells in 3D cultures exhibited higher VEGFR2 expression levels, accelerated migration, invasion, and disorganized sprout formation in response to elevated IL-6 levels secreted by tumor myoepithelial (Epi-T) cells. Constitutively, compared with normal endothelial (Endo-N) cells, Endo-T cells differentially expressed DNA methyltransferase isoforms and had increased levels of IL-6 signaling intermediates such as IL-6R and signal transducer and activator of transcription 3 (STAT3). Upon IL-6 treatment, Endo-N and Endo-T cells displayed altered expression of the DNA methyltransferase 1 (DNMT1) isoform. Mechanistic studies revealed that IL-6 induced proteasomal degradation of DNMT1, but not of DNMT3A and DNMT3B and subsequently led to promoter hypomethylation and expression/activation of VEGFR2. IL-6-induced VEGFR2 up-regulation was inhibited by overexpression of DNMT1. Transfection of a dominant-negative STAT3 mutant, but not of STAT1, abrogated VEGFR2 expression. Our results indicate that in the breast tumor microenvironment, IL-6 secreted from myoepithelial cells influences DNMT1 stability, induces the expression of VEGFR2 in endothelial cells via a promoter methylation-dependent mechanism, and leads to disordered angiogenesis.

VEGF-A in Cardiomyocytes and Heart Diseases.

The vascular endothelial growth factor (VEGF), a homodimeric vasoactive glycoprotein, is the key mediator of angiogenesis. Angiogenesis, the formation of new blood vessels, is responsible for a wide variety of physio/pathological processes, including cardiovascular diseases (CVD). Cardiomyocytes (CM), the main cell type present in the heart, are the source and target of VEGF-A and express its receptors, VEGFR1 and VEGFR2, on their cell surface. The relationship between VEGF-A and the heart is double-sided. On the one hand, VEGF-A activates CM, inducing morphogenesis, contractility and wound healing. On the other hand, VEGF-A is produced by CM during inflammation, mechanical stress and cytokine stimulation. Moreover, high concentrations of VEGF-A have been found in patients affected by different CVD, and are often correlated with an unfavorable prognosis and disease severity. In this review, we summarized the current knowledge about the expression and effects of VEGF-A on CM and the role of VEGF-A in CVD, which are the most important cause of disability and premature death worldwide. Based on clinical studies on angiogenesis therapy conducted to date, it is possible to think that the control of angiogenesis and VEGF-A can lead to better quality and span of life of patients with heart disease.

Role of NDEL1 and VEGF/VEGFR-2 in Mouse Hippocampus After Status Epilepticus.

Nuclear-distribution element-like 1 (NDEL1) is associated with the proliferation and migration of neurons. Vascular endothelial growth factor (VEGF) in combination with VEGF receptor-2 (VEGFR-2) regulates the proliferation and migration of neurons. This study was performed to explore undefined alterations in the expression levels of NDEL1 and VEGF/VEGFR-2 within the hippocampus after status epilepticus (SE). Following the creation of pilocarpine-induced epilepsy models using adolescent male C57BL/6 mice, Western blotting and reverse transcription quantitative polymerase chain reaction were applied to assess the levels of NDEL1, VEGF, and VEGFR-2 expression in whole hippocampi at 1, 2, 3, and 4 weeks post-SE, respectively. Immunofluorescent labeling was also employed to detect the colocalization of NDEL1 and VEGF in the hippocampus. Our results indicated that NDEL1 and VEGF have similar patterns of upregulation throughout the hippocampus. Upregulation of VEGFR-2 occurred only in the early stages, and the expression decreased shortly afterward. NDEL1 and VEGF were coexpressed in the cornu ammonis 3 pyramidal cell, granular, and polymorph layers of the dentate gyrus in the hippocampus. This study revealed that NDEL1, VEGF, and VEGFR-2 may work together and are involved in the pathophysiology in the hippocampus after SE.

Substance P accelerates the progression of human esophageal squamous cell carcinoma via MMP-2, MMP-9, VEGF-A, and VEGFR1 overexpression.

Tachykinins such as Substance P (SP) are a group of neuropeptides that are involved in cancer development. Neurokinin-1 receptor (NK-1R) is the main tachykinin receptor mediating the effects of SP, which is overexpressed in human esophageal squamous cell carcinoma (ESCC) and other malignant tissues. However, the effects of SP/NK-1R system on the migration of esophageal cancer cells and angiogenesis is not clear yet. This study seeks to obtain data to address these research gaps. In order to assess the effects of the FDA-approved aprepitant drug, a commercially available NK-1R antagonist, on the viability of KYSE-30 ESCC cells, resazurin assay was performed. The influence of SP/NK-1R system on the migration potential of these cells was examined using scratch assay. The effects of this system on the expression levels of metastatic factors were also examined by RT-PCR and western blot analyses. The half-maximal inhibitory concentration (IC50) value for KYSE-30 cells treated with aprepitant found to be 29.88 µM. Treatment with SP significantly promoted KYSE-30 esophageal cancer cell migration, and aprepitant blocked this effect. In addition, SP significantly induced the expression of matrix metalloproteinase-2 (MMP-2), MMP-9, vascular endothelial growth factor-A (VEGF-A), and VEGF receptor1 (VEGFR1) in the cells, whereas aprepitant inhibited the up-regulation effects caused by SP. SP plays important roles in the development of human esophageal squamous cell carcinoma by promoting cancer cell invasion and enhancing the expression of factors involved in cellular migration and angiogenesis, which can be blocked by the NK-1R antagonist, aprepitant.

Neonatal excitotoxicity modifies blood-brain barrier properties increasing its susceptibility to hypertonic shock in adulthood.

Early responses to a neurological excitotoxic process include blood-brain barrier (BBB) impairment and overexpression of vascular endothelial growth factor (VEGF), but the long-term effects of excitotoxicity on the BBB properties remain unknown. To assess this, we induced an excitotoxic process on male rats by neonatal monosodium glutamate (MSG) treatment. At postnatal day (PD) 60, we measured the expression level of structural proteins of the BBB and the VEGF type-2 receptor (VEGFR-2) protein in the cerebral motor cortex (CMC), striatum (STR), hippocampus (Hp), entorhinal cortex (Ent), and hypothalamus (Hyp). We also measured BBB permeability in the same cerebral regions. Neonatal MSG treatment significantly reduced the protein expression level of claudin-5 in the CMC, and of ZO-1 in the CMC and Hp, and increased the expression level of plasmalemmal vesicle-associated protein in the CMC, and of VEGFR-2 in all regions except for the Hyp. BBB permeability was significantly higher in all studied regions of MSG-treated animals after hypertonic shock (HS). The increased BBB permeability observed in the MSG-treated animals after HS was reversed by VEGFR-2 inhibition with SU5416. We conclude that neonatal excitotoxicity leads to lasting impairment on BBB properties in adulthood, increasing its susceptibility to HS that could be regulated by VEGFR-2 activity inhibition.

Purinergic P2Y2 receptors modulate endothelial sprouting.

Purinergic P2 receptors are critical regulators of several functions within the vascular system, including platelet aggregation, vascular inflammation, and vascular tone. However, a role for ATP release and P2Y receptor signalling in angiogenesis remains poorly defined. Here, we demonstrate that blood vessel growth is controlled by P2Y2 receptors. Endothelial sprouting and vascular tube formation were significantly dependent on P2Y2 expression and inhibition of P2Y2 using a selective antagonist blocked microvascular network generation. Mechanistically, overexpression of P2Y2 in endothelial cells induced the expression of the proangiogenic molecules CXCR4, CD34, and angiopoietin-2, while expression of VEGFR-2 was decreased. Interestingly, elevated P2Y2 expression caused constitutive phosphorylation of ERK1/2 and VEGFR-2. However, stimulation of cells with the P2Y2 agonist UTP did not influence sprouting unless P2Y2 was constitutively expressed. Finally, inhibition of VEGFR-2 impaired spontaneous vascular network formation induced by P2Y2 overexpression. Our data suggest that P2Y2 receptors have an essential function in angiogenesis, and that P2Y2 receptors present a therapeutic target to regulate blood vessel growth.

Development of pyogenic granuloma with strong vascular endothelial growth factor receptor-2 expression during ramucirumab treatment.

The angiogenesis inhibitor ramucirumab (IMC-1121B) is a fully humanised IgG1 monoclonal antibody targeting the extracellular domain of vascular endothelial growth factor receptor 2. Ramucirumab has been approved as a second-line treatment for lung cancer. Pyogenic granuloma is an acquired, benign vascular tumour of the skin or mucous membrane. We encountered a patient with pyogenic granuloma who was treated with ramucirumab. The patient was a 48-year-old Japanese woman with advanced lung cancer who had been heavily pretreated using several lines of chemotherapy. Ramucirumab was administered as the fifth-line treatment with docetaxel. After 10 days, a painless rice-coloured or pink papule appeared on her finger. One month later, it increased in size to 20 mm. We examined the pathological condition by immunostaining using the resected specimen diagnosed as pyogenic granuloma. Paradoxically, this vascular tumour arose during the administration of an angiogenesis inhibitor.

Vascular Endothelial Growth Factor A Signaling Promotes Spinal Central Sensitization and Pain-related Behaviors in Female Rats with Bone Cancer.

BACKGROUND: Cancer pain is a pervasive clinical symptom impairing life quality. Vascular endothelial growth factor A has been well studied in tumor angiogenesis and is recognized as a therapeutic target for anti-cancer treatment. This study tested the hypothesis that vascular endothelial growth factor A and vascular endothelial growth factor receptor 2 contribute to bone cancer pain regulation associated with spinal central sensitization. METHODS: This study was performed on female rats using a metastatic breast cancer bone pain model. Nociceptive behaviors were evaluated by mechanical allodynia, thermal hyperalgesia, spontaneous pain, and CatWalk gait analysis. Expression levels were measured by real-time quantitative polymerase chain reaction, western blot, and immunofluorescence analysis. Excitatory synaptic transmission was detected by whole-cell patch-clamp recordings. The primary outcome was the effect of pharmacologic intervention of spinal vascular endothelial growth factor A/vascular endothelial growth factor receptor 2-signaling on bone cancer pain behaviors. RESULTS: The mRNA and protein expression of vascular endothelial growth factor A and vascular endothelial growth factor receptor 2 were upregulated in tumor-bearing rats. Spinal blocking vascular endothelial growth factor A or vascular endothelial growth factor receptor 2 significantly attenuated tumor-induced mechanical allodynia (mean ± SD: vascular endothelial growth factor A, 7.6 ± 2.6 g vs. 5.3 ± 3.3 g; vascular endothelial growth factor receptor 2, 7.8 ± 3.0 g vs. 5.2 ± 3.4 g; n = 6; P < 0.0001) and thermal hyperalgesia (mean ± SD: vascular endothelial growth factor A, 9.0 ± 2.4 s vs. 7.4 ± 2.7 s; vascular endothelial growth factor receptor 2, 9.3 ± 2.5 s vs. 7.5 ± 3.1 s; n = 6; P < 0.0001), as well as spontaneous pain and abnormal gaits. Exogenous vascular endothelial growth factor A enhanced excitatory synaptic transmission in a vascular endothelial growth factor receptor 2-dependent manner, and spinal injection of exogenous vascular endothelial growth factor A was sufficient to cause pain hypersensitivity via vascular endothelial growth factor receptor 2-mediated activation of protein kinase C and Src family kinase in naïve rats. Moreover, spinal blocking vascular endothelial growth factor A/vascular endothelial growth factor receptor 2 pathways suppressed protein kinase C-mediated N-methyl-D-aspartate receptor activation and Src family kinase-mediated proinflammatory cytokine production. CONCLUSIONS: Vascular endothelial growth factor A/vascular endothelial growth factor receptor 2 contributes to central sensitization and bone cancer pain via activation of neuronal protein kinase C and microglial Src family kinase pathways in the spinal cord.

Biochemical and Conformational Characterization of Recombinant VEGFR2 Domain 7.

Angiogenesis is a biological process finely tuned by a plethora of pro- and anti-angiogenic molecules, among which vascular endothelial growth factors (VEGFs). Their biological activity is expressed through the interaction with three cognate receptor tyrosine kinases, VEGFR1, 2, and 3. VEGFR2 is the primary regulator of angiogenesis. Ligand-induced VEGFR2 dimerization and activation depend on direct ligand binding to extracellular domains 2 and 3 of receptor and in the establishment of interactions between proximal membrane domains. VEGFR2 domain 7 has been shown to play a crucial role in receptor dimerization and regulation, therefore, representing a convenient target for the allosteric modulation of VEGFR2 activity. The ability to prepare a functional VEGFR2D7 domain represents the starting point to the development of novel VEGFR2 binders acting as allosteric inhibitors of receptor activity. Here, we describe a robust and efficient procedure for the preparation in E. coli of the VEGFR2 domain 7. The protein was obtained with a good yield and was properly folded. It was investigated in a biochemical and structural study, providing information on its conformational arrangement and in solution properties.

Vascular endothelial growth factor receptor 2 (VEGFR2) correlates with long-term survival in patients with advanced high-grade serous ovarian cancer (HGSOC): a study from the Tumor Bank Ovarian Cancer (TOC) Consortium.

OBJECTIVE: The impact of angiogenesis on long-term survival of high-grade serous ovarian cancer (HGSOC) patients remains unclear. This study investigated whether angiogenic markers correlated with 5-year progression-free survival (PFS) in a large cohort of matched advanced HGSOC tissue samples. METHODS: Tumor samples from 124 primary HGSOC patients were retrospectively collected within the Tumor Bank Ovarian Cancer ( http://www.toc-network.de ). All patients were in advanced stages (FIGO stage III-IV). No patient had received anti-angiogenesis therapy. The cohort contains 62 long-term survivors and 62 controls matched by age and post-surgical tumor residuals. Long-term survivors were defined as patients with no relapse within 5 years after the end of first-line chemotherapy. Controls were patients who suffered from first relapse within 6-36 months after primary treatment. Samples were assessed for immunohistochemical expression of vascular endothelial growth factor (VEGF) A and VEGF receptor 2 (VEGFR2). Expression profiles of VEGFA and VEGFR2 were compared between the two groups. RESULTS: Significant correlation between VEGFA and VEGFR2 expression was observed (p < 0.0001, Spearman coefficient 0.347). A high expression of VEGFR2 (VEGFR2high) was found more frequently in long-term survivors (77.4%, 48/62) than in controls (51.6%, 30/62, p = 0.001), independent of FIGO stage and VEGFA expression in multivariate analysis (p = 0.005). Also, VEGFR2high was found the most frequently in women with PFS ≥ 10 years (p = 0.001) among all 124 patients. However, no significant association was detected between VEGFA expression and 5-year PFS (p = 0.075). CONCLUSIONS: VEGFR2 overexpression significantly correlated with long-term PFS in HGSOC patients, independent of age, FIGO stage, tumor residual and VEGFA expression.

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.

Co-ordinated expression of the VEGF system components in granulosa cells to develop a proangiogenic autocrine milieu during ovarian follicle development.

In the present study, we investigated the temporal relationship between angiogenic and antiangiogenic vascular endothelial growth factor isoforms (VEGFxxxa and VEGFxxxb, respectively), the receptors VEGFR1 and VEGFR2, their soluble forms, and the kinases and the splicing factors regulating the synthesis of VEGF isoforms in healthy and atretic antral follicles. The results show a higher (p < 0.05) messenger RNA (mRNA) expression of VEGF120a, VEGF164a, and VEGF120b in healthy than in atretic follicles, but the mRNA expression of VEGF164b was not detected. The mRNA of serine-arginine protein kinase 1 ( SRPK1) was higher ( p < 0.05) in large healthy follicles than in large atretic follicles. In contrast, atretic follicles had higher mRNA expression of a soluble form of the receptor 2 of VEGF ( sVEGFR2) than healthy follicles ( p < 0.05). Additionally, we observed a positive relationship ( p < 0.05) between SRPK1 and serine-arginine-rich splicing factor 1 ( SRSF1) with the angiogenic isoforms VEGF120a and VEGF164a and between CDC-like kinases-1 ( CLK1) and SRSF6 with the antiangiogenic VEGF120b isoform. Principal components analysis (PCA) resulted in two PC explaining 71% of the variation, which was formed by the VEGF isoforms, the kinases and the splicing factor (PC1) and by the VEGF receptors (PC2). When PC analysis was carried out within follicular health status, there were no differences for PC1 between follicular status, whereas PC2 differed between healthy and atretic follicles. In conclusion, the higher mRNA expression for VEGF120a and VEGF164a, the low expression of sVEGFR2, and absent expression of mRNA for VEGF164b provide evidence of a proangiogenic autocrine milieu to support granulosa cells during follicle development.

VEGF receptor-1 modulates amyloid ß 1-42 oligomer-induced senescence in brain endothelial cells.

Aggregated amyloid ß (Aß) peptides in the Alzheimer's disease (AD) brain are hypothesized to trigger several downstream pathologies, including cerebrovascular dysfunction. Previous studies have shown that Aß peptides can have antiangiogenic properties, which may contribute to vascular dysfunction in the early stages of the disease process. We have generated data showing that brain endothelial cells (ECs) exposed to toxic Aß1-42 oligomers can readily enter a senescence phenotype. To determine the effect of Aß oligomers on brain ECs, we treated early passaged human brain microvascular ECs and HUVECs with high MW Aß1-42 oligomers (5 µM, for 72 h). For controls, we used no peptide treatment, 5 µM Aß1-42 monomers, and 5 µM Aß1-42 fibrils, respectively. Brain ECs treated with Aß1-42 oligomers showed increased senescence-associated ß-galactosidase staining and increased senescence-associated p21/p53 expression. Treatment with either Aß1-42 monomer or Aß1-42 fibrils did not induce senescence in this assay. We then measured vascular endothelial growth factor receptor (VEGFR) expression in the Aß1-42 oligomer-treated ECs, and these cells showed significantly increased VEGFR-1 expression and decreased VEGFR-2 levels. Overexpression of VEGFR-1 in brain ECs readily induced senescence, suggesting a direct role of VEGFR-1 signaling events in this paradigm. More importantly, small interfering RNA-mediated knockdown of VEGFR-1 expression in brain ECs was able to prevent up-regulation of p21 protein expression and significantly reduced induction of senescence following Aß1-42 oligomer treatment. Our studies show that exposure to Aß1-42 oligomers may impair vascular functions by altering VEGFR-1 expression and causing ECs to enter a senescent phenotype. Altered VEGFR expression has been documented in brains of AD patients and suggests that this pathway may play a role in AD disease pathogenesis. These studies suggest that modulating VEGFR-1 expression and signaling events could potentially prevent senescence and rejuvenate EC functions, and provides us with a novel target to pursue for prevention and treatment of cerebrovascular dysfunction in AD.-Angom, R. S., Wang, Y., Wang, E., Pal, K., Bhattacharya, S., Watzlawik, J. O., Rosenberry, T. L., Das, P., Mukhopadhyay, D. VEGF receptor-1 modulates amyloid ß 1-42 oligomer-induced senescence in brain endothelial cells.

VEGFR2 and VEGF-C Suppresses the Epithelial-Mesenchymal Transition Via YAP in Retinal Pigment Epithelial Cells.

BACKGROUND: Whereas retinal pigment epithelial (RPE) cells are known to secrete VEGF-A and VEGFR2, the functions of the autocrine VEGF signaling remain unclear. Meanwhile, anti-VEGF therapies have been applied routinely to treat ocular vascular diseases. OBJECTIVE: The aim of this study was to determine the functions of the VEGF signaling in RPE cells and evaluate the consequences of its interruption. METHODS: The genes involved in the VEGF and Hippo signal pathways were knocked down with siRNAs in both ARPE-19 cell line and human primary RPE cells via transient transfection whereas overexpression of VEGFR2 was mediated via adenovirus transduction. Expression of the epithelial-mesenchymal transition (EMT) markers and the downstream genes of YAP were determined by real-time PCR and Western Blot analysis. Immunofluorescence staining was utilized to determine gene expression in tissue and mouse samples. RESULTS: Knockdown of VEGFR2 results in epithelial-mesenchymal transition in vitro and in vivo. Overexpression of VEGFR2 suppresses TGF ß-mediated EMT in RPE cells. Loss of VEGF-C rather than VEGF-A induces EMT. Mechanistically, the VEGFR2 ablation-induced EMT in RPE cells is mediated by activation of YAP, an effector of the Hippo pathway. Finally, the immunohistochemical analysis of VEGFR2 and YAP in human proliferative vitreoretinopathy (PVR) membranes indicates a tendency of an inverse correlation between VEGFR2-positive and YAP-positive cells. CONCLUSIONS: Our results disclose unexpected novel roles of VEGFR2 and VEGF-C in the process of EMT of RPE cells and in the Hippo pathway. The data shown here demonstrated that VEGFR2 and VEGF-C are important to maintain the normal physiological state of RPE cells.

CT textural analysis of gastric cancer: correlations with immunohistochemical biomarkers.

To investigate the ability of CT texture analysis to assess and predict the expression statuses of E-cadherin, Ki67, VEGFR2 and EGFR in gastric cancers, the enhanced CT images of 139 patients with gastric cancer were retrospectively reviewed. The region of interest was manually drawn along the margin of the lesion on the largest slice in the arterial and venous phases, which yielded a series of texture parameters. Our results showed that the standard deviation, width, entropy, entropy (H), correlation and contrast from the arterial and venous phases were significantly correlated with the E-cadherin expression level in gastric cancers (all P < 0.05). The skewness from the arterial phase and the mean and autocorrelation from the venous phase were negatively correlated with the Ki67 expression level in gastric cancers (all P < 0.05). The width, entropy and contrast from the venous phase were positively correlated with the VEGFR2 expression level in gastric cancers (all P < 0.05). No significant correlation was found between the texture features and EGFR expression level. CT texture analysis, which had areas under the receiver operating characteristic curve (AUCs) ranging from 0.612 to 0.715, holds promise in predicting E-cadherin, Ki67 and VEGFR2 expression levels in gastric cancers.

VEGF-A/VEGFR-2 and FGF-2/FGFR-1 but not PDGF-BB/PDGFR-ß play important roles in promoting immature and inflammatory intraplaque angiogenesis.

Various angiogenic factors have been shown to play important roles in intraplaque angiogenesis, while little is known about the dynamic expression change and interplay between various angiogenic factors and intraplaque angiogenesis under high cholesterol conditions. New Zealand rabbits underwent balloon injury of the abdominal artery and then were assigned to a control group (n = 15, normal chow) or high cholesterol group (n = 25, 1% high cholesterol diet). At weeks 4, 6, 8, 10, and 12 after acclimation, rabbits (high cholesterol group, n = 5; control group, n = 3) were euthanized. No lesions were observed in the control group. From week 4 to week 12, the expression of vascular endothelial growth factor A (VEGF-A), VEGF receptor 2 (VEGFR-2), fibroblast growth factor 2 (FGF-2), FGF receptor 1 (FGFR-1), platelet-derived growth factor-BB (PDGF-BB), and tumor necrosis factor alpha (TNF-α), the vulnerability index (VI) and the microvessel density (MVD) were significantly elevated in the high cholesterol group; however, PDGF receptor ß (PDGFR-ß) expression showed little change. Analysis by double-label immunofluorescence (CD31 and Ng2) and FITC-dextran indicated that the neovessels within the plaque were leaky due to a lack of pericytes. As indicated by Pearson's correlation analysis, there was a highly positive correlation between the VI, MVD, macrophage content, and TNF-α level, and the levels of VEGF-A/VEGFR-2 and FGF-2/FGFR-1. However, no correlations were observed between PDGFR-ß levels and the VI or MVD. High expression of VEGF-A/VEGFR-2 and FGF-2/FGFR-1 but not of PDGF-BB/PDGFR-ß may contribute to immature and inflammatory intraplaque angiogenesis and plaque instability in a rabbit model of atherosclerosis.

Ionic silicon improves endothelial cells' survival under toxic oxidative stress by overexpressing angiogenic markers and antioxidant enzymes.

Oxidative stress, induced by harmful levels of reactive oxygen species, is a common occurrence that impairs proper bone defect vascular healing through the impairment of endothelial cell function. Ionic silicon released from silica-based biomaterials, can upregulate hypoxia-inducible factor-1α (HIF-1α). Yet it is unclear whether ionic Si can restore endothelial cell function under oxidative stress conditions. Therefore, we hypothesized that ionic silicon can help improve human umbilical vein endothelial cells' (HUVECs') survival under toxic oxidative stress. In this study, we evaluated the ionic jsilicon effect on HUVECs viability, proliferation, migration, gene expression, and capillary tube formation under normal conditions and under harmful hydrogen peroxide levels. We demonstrated that 0.5-mM Si4+ significantly enhanced angiogenesis in HUVECs under normal condition (p < 0.05). HUVECs exposed to 0.5-mM Si4+ presented a morphological change, even without the bed of Matrigel, and formed significantly more tube-like structures than the control (p < 0.001). In addition, 0.5-mM Si4+ enhanced cell viability in HUVECs under harmful H2 O2 levels. HIF-1α, vascular endothelial growth factor-A, and vascular endothelial growth factor receptor-2 were overexpressed more than twofold in silicon-treated HUVECs, under normal and toxic H2 O2 conditions. Moreover, the HUVECs were treated with 0.5-mM Si4+ overexpressed superoxide dismutase-1 (SOD-1), catalase-1 (Cat-1), and nitric oxide synthase-3 (NOS3) under normal and oxidative stress environment (p < 0.01). A computational model was used for explaining the antioxidant effect of Si4+ in endothelial cells and human periosteum cells by SOD-1 enhancement. In conclusion, we demonstrated that 0.5-mM Si4+ can recover the HUVECs' viability under oxidative stress conditions by reducing cell death and upregulating expression of angiogenic and antioxidant factors.