The pathological roles and potential mechanisms of vascular endothelial growth factor receptor-3 in gastric cancer.

OBJECTIVE: To investigate the roles and underlying mechanisms of vascular endothelial growth factor receptor-3 (VEGFR-3) in gastric cancer (GC). METHODS: VEGFR-3 gene expression profiles in human gastric adenocarcinoma (GAC) tissues were analysed using The Cancer Genome Atlas database. Human GC cell lines and were used for in vitro studies. Mouse models of GC and distant metastasis were used for in vivo studies. Silencing of VEGFR-3 gene expression was achieved using small interfering RNA. RESULTS: VEGFR-3 gene expression was significantly elevated in GAC tissues and GC cells. Higher VEGFR-3 expression was positively correlated with more advanced stages and a greater number of metastatic lymph nodes. In vitro studies in GC cells showed that knockdown of VEGFR-3 gene expression significantly suppressed cell proliferation and migration, but promoted apoptosis. In vivo investigations revealed that silencing of VEGFR-3 gene expression exhibited significant inhibition on tumour growth and metastasis. Further mechanistic studies showed that VEGFR-3 exerted its pathological roles by affecting the key molecules in the apoptotic and epithelial-mesenchymal transition pathways. CONCLUSION: The molecular pathways associated with VEGFR-3-mediated pathological effects could be targets in the development of novel approaches for the diagnosis, prognosis and treatment of GC.

Mechanism of the HIF-1α/VEGF/VEGFR-2 pathway in the proliferation and apoptosis of human haemangioma endothelial cells.

Haemangiomas (HAs) are prevalent vascular endothelial cell tumours. With respect to the possible involvement of HIF-1α in HAs, we have explored its role in haemangioma endothelial cell (HemEC) proliferation and apoptosis. shRNA HIF-1α and pcDNA3.1 HIF-α were manipulated into HemECs. HIF-α, VEGF, and VEGFR-2 mRNA and protein levels were assessed by qRT-PCR and Western blotting. Cell proliferation and viability, cell cycle and apoptosis, migration and invasion, and ability to form tubular structures were assessed by colony formation assay, CCK-8, flow cytometry, Transwell assay, and tube formation assay. Cell cycle-related protein levels, and VEGF and VEGFR-2 protein interaction were detected by Western blot and immunoprecipitation assays. An Haemangioma nude mouse model was established by subcutaneous injection of HemECs. Ki67 expression was determined by immunohistochemical staining. HIF-1α silencing suppressed HemEC neoplastic behaviour and promoted apoptosis. HIF-1α facilitated VEGF/VEGFR-2 expression and the VEGF had interacted with VEGFR-2 at protein - protein level. HIF-1α silencing arrested HemECs at G0/G1 phase, diminished Cyclin D1 protein level, and elevated p53 protein level. VEGF overexpression partially abrogated the effects of HIF-1α knockdown on inhibiting HemEC malignant behaviours. Inhibiting HIF-1α in nude mice with HAs repressed tumour growth and Ki67-positive cells. Briefly, HIF-1α regulated HemEC cell cycle through VEGF/VEGFR-2, thus promoting cell proliferation and inhibiting apoptosis.

Eplerenone Prevents Cardiac Fibrosis by Inhibiting Angiogenesis in Unilateral Urinary Obstruction Rats.

Introduction: Cardiovascular disease constitutes the leading cause of mortality in patients with chronic kidney disease (CKD), which is termed cardiorenal syndrome type 4 (CRS-4). Here, we report the development of pathological cardiac remodeling and fibrosis in unilateral urinary obstruction (UUO) rats. Methods: Hematoxylin and eosin (H&E) staining was performed to observe the pathology of myocardial tissue. The degree of myocardial tissue fibrosis was observed by Masson and Sirius red staining. Immunohistochemical staining was applied to detect the expression of CD34 and CD105 in myocardial tissue, and immunofluorescent staining was performed to examine the expression of CD34, collagen I/collagen III, and alpha smooth muscle actin (α-SMA). The expression of the signal pathway-related proteins vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor receptor 2 (VEGFR2), nuclear factor κB (NF-κB), and interleukin (IL)-1ß was tested by western blotting. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the mRNA levels of serum and glucocorticoid-inducible kinase (SGK)-1, NF-κB, and interleukin-1ß (IL-1ß). Results: The results showed the development of pathological cardiac remodeling and cardiac dysfunction in UUO rats. Moreover, there was more angiogenesis and endothelial-mesenchymal transition (End-MT) in the UUO group, and these effects were inhibited by eplerenone. Conclusions: The results indicated that this cardiac fibrosis was associated with angiogenesis and that End-MT was related to aldosterone and mineralocorticoid receptor (MR) activation. Moreover, in association with the MR/IL-1ß/VEGFA signaling pathway, early treatment with the MR antagonist eplerenone in rats with UUO-induced CKD may significantly attenuate MR activation and cardiac fibrosis.

Effects of plant-based medicinal food on postoperative recurrence and lung metastasis of gastric cancer regulated by Wnt/ß-catenin-EMT signaling pathway and VEGF-C/D-VEGFR-3 cascade in a mouse model.

BACKGROUND: The plant-based medicinal food (PBMF) is a functional compound extracted from 6 medicinal and edible plants: Coix seed, L. edodes, A. officinalis L., H. cordata, Dandelion, and G. frondosa. Our previous studies have confirmed that the PBMF possesses anti-tumor properties in a subcutaneous xenograft model of nude mice. This study aims to further investigate the effects and potential molecular mechanisms of the PBMF on the recurrence and metastasis of gastric cancer (GC). METHODS: Postoperative recurrence and metastasis model of GC was successfully established in inbred 615 mice inoculated with mouse forestomach carcinoma (MFC) cells. After tumorectomy, 63 GC mice were randomly divided into five groups and respectively subject to different treatments for 15 days as below: model control group, 5-Fu group, and three doses of PBMF (43.22, 86.44, 172.88 g/kg PBMF in diet respectively). The inhibition rate (IR) of recurrence tumor weights and organ coefficients were calculated. Meanwhile, histopathological changes were examined and the metastasis IR in lungs and lymph node tissues was computed. The mRNA expressions related to the canonical Wnt/ß-catenin signaling pathway, epithelial-mesenchymal transition (EMT) and lymphangiogenesis were detected by RT-qPCR in recurrence tumors and/or lung tissues. Protein expressions of ß-catenin, p-ß-catenin (Ser33/37/Thr41), GSK-3ß, p-GSK-3ß (Ser9), E-cadherin, and Vimentin in recurrence tumors were determined by Western Blot. LYVE-1, VEGF-C/D, and VEGFR-3 levels in recurrence tumors and/or lung tissues were determined by immunohistochemistry staining. RESULTS: The mRNA, as well as protein expression of GSK-3ß were up-regulated and the mRNA expression of ß-catenin was down-regulated after PBMF treatment. Meanwhile, the ratio of p-ß-catenin (Ser33/37/Thr41) to ß-catenin protein was increased significantly and the p-GSK-3ß (Ser9) protein level was decreased. And PMBF could effectively decrease the mRNA and protein levels of Vimentin while increasing those of E-cadherin. Furthermore, PBMF markedly reduced lymphatic vessel density (LVD) (labeled by LYVE-1) in recurrence tumor tissues, and mRNA levels of VEGF-C/D, VEGFR-2/3 of recurrence tumors were all significantly lower in the high-dose group. CONCLUSIONS: PBMF had a significant inhibitory effect on recurrence and lung metastasis of GC. The potential mechanism may involve reversing EMT by inhabiting the Wnt/ß-catenin signaling pathway. Lymphatic metastasis was also inhibited by PBMF via down-regulating the activation of the VEGF-C/D-VEGFR-2/3 signaling cascade.

Apatinib Through Activating the RhoA/ROCK Signaling Pathway to Cause Dysfunction of Vascular Smooth Muscle Cells.

Vascular smooth muscle cells (VSMCs) are associated with differentiated, organized, and contractile phenotype under the effect of various types of physiological conditions those are associated with migratory, proliferative, and synthetic phenotype under the effect of various types of stimuli, which dysfunction drives many cardiovascular diseases. Abnormal cell proliferation and invasion of VSMCs are among the primary causes of hypertension. Apatinib is a small-molecule tyrosine kinase inhibitor (TKI) that highly selectively binds to and strongly inhibits VEGFR-2. Previous studies have confirmed that the TKIs can raise blood pressure through RhoA/ROCK pathway. LARG is a key gene in the RhoA/ROCK pathway and plays a critical role in the continuous vasoconstriction function because it regulates part of signal transduction in VSMCs. In this study, an in vitro experiment was conducted to observe that apatinib caused dysfunction of MOVAS cells through the RhoA/ROCK signalling pathway and Y27632, a nonspecific ROCK inhibitor, and knockout of LARG gene can improve the proliferation, antiapoptosis, oxidative stress, and mitochondrial autophagy of apatinib-induced MOVAS cells. These findings suggest that activation of the RhoA/ROCK signalling pathway could be the underlying mechanism of apatinib-induced dysfunction of MOVAS cells, while ROCK inhibitor and knockout of LARG gene have potential therapeutic value.

Design, synthesis and molecular docking of new [1,2,4] triazolo[4,3-a]quinoxaline derivatives as anticancer agents targeting VEGFR-2 kinase.

Vascular endothelial growth factor receptor-2 (VEGFR-2) is critically involved in cancer angiogenesis. Blocking of VEGFR-2 signaling pathway proved effective suppression of tumor growth. Accordingly, two series of new triazoloquinoxaline-based derivatives were designed and synthesized as VEGFR-2 inhibitors. All in vitro cytotoxic activities of the synthesized compounds were evaluated against two human cancer cell lines (MCF-7 and HepG2). To confirm the potential mechanism of cytotoxicity, enzymatic assays against VEGFR-2 were estimated for all the target compounds. The results of VEGFR-2 inhibitory activity and cytotoxicity were in high correlation. Compound 22a exhibited the highest cytotoxic effect with IC50 values of 6.2 and 4.9 µM against MCF-7 and HepG2, respectively, comparing to sorafenib (IC50 = 3.53 and 2.18 µM). Such derivative showed the best VEGFR-2 inhibitory activity with an IC50 value of 3.9 nM, which is very close to that of sorafenib (IC50 = 3.13 nM). Moreover, compounds 22b, 23b, and 23e exhibited strong cytotoxic activity with IC50 values ranging from 11.7 to 15.3 µM. Also, these compounds showed promising VEGFR-2 inhibition with IC50 values of 4.2, 5.7, and 4.7 nM, respectively. In silico docking, ADMET, and toxicity studies were carried out for the synthesized compounds. The results revealed that some compounds have a good binding mode against VEGFR-2 and a high level of drug-likeness.

In vitro and in silico growth inhibitory, anti-ovarian & anti-lung carcinoma effects of 1,5 diarylpenta-1,4-dien-3-one as synthetically modified curcumin analogue.

The synthesized 1,5 diarylpenta-1,4-dien-3-one derivatives (compounds 1-6) as synthetic curcumin analogues were tested for their potential anticancer activity against human ovarian and lung adenocarcinoma cells. The absorption, distribution, metabolism, excretion, and toxicity (ADMET/pharmacokinetic) parameters of all the compounds were predicted by admetSAR software. The pharmacokinetics, pharmacodynamics and bioactivity scores properties based on Lipinski rule and Ghose filter, calculated with the help of Molinspiration and ChemDraw. Molecular docking evaluation of all the compounds was also performed by using AutoDock Vina and iGEMDOCK against three most common human anticancer targets; epidermal growth factor receptor (EGFR), heat shock protein (Hsp 90-α), and vascular endothelial growth factor receptor-2 (VEGFR2). The obtained results were compared with the reference compound 7 and drugs 8-10 (7: GO-035; 8: Quinazolin; 9: Naquotinib and 10: Ribofuranuronamide). Finding indicates, all the compounds were potentially interacting with VEGFR2 through the average -9.1 binding energy (BE) with closer contact <5.0 Å deep in the active site of the ligand-receptor complex. All the compounds showed excellent oral bioavailability, bioactivity score, and none of the compounds are virtually found to be toxic. Compounds 1-6 were also successfully characterized by the physical properties as well as spectroscopic techniques (FT-IR and 1H-NMR). In vitro anti-proliferative activity was tested via MTT method against human ovarian carcinoma (PA-1) and human lung adenocarcinoma (A549) cells and further screened for apoptotic parameters such as nuclear fragmentation and ROS generation. Compound 4 exhibits good dose-dependent anti-proliferative activity (IC50 73 and 79.7 µM) against human ovarian carcinoma and human lung adenocarcinoma, respectively.Communicated by Ramaswamy H. Sarma.

Synthesis, characterization, biological evaluation and molecular docking of a new quinazolinone-based derivative as a potent dual inhibitor for VEGFR-2 and EGFR tyrosine kinases.

An efficient process for the preparation of a new ethyl 2-((3-(4-fluorophenyl)-6-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio) acetate (5) was described. The prepared derivative was synthesized using the S-arylation method. Several analytical techniques, such as NMR, Raman and infrared spectroscopy, were used to characterize this compound. The compound was screened for cytotoxic activity against three human cancer cell lines: human cervical cancer (HeLa), human lung adenocarcinoma (A549) and triple negative breast cancer (MDA-MB-231) cells using an MTT assay. It exhibited potent cytotoxic activity against the tested cell lines with IC50 values in the low micromolar range when compared to a standard drug, docetaxel. It also displayed potent inhibitory activity towards VEGFR-2 and EGFR tyrosine kinases, reflecting its potential to act as an effective anti-cancer agent.Communicated by Ramaswamy H. Sarma.

FUNDC1-dependent mitochondria-associated endoplasmic reticulum membranes are involved in angiogenesis and neoangiogenesis.

FUN14 domain-containing protein 1 (FUNDC1) is an integral mitochondrial outer-membrane protein, and mediates the formation of mitochondria-associated endoplasmic reticulum membranes (MAMs). This study aims to determine the contributions of FUNDC1-mediated MAMs to angiogenesis in vitro and in vivo. In cultured endothelial cells, VEGF significantly increases the formation of MAMs and MAM-related proteins, including FUNDC1. Endothelial cell-specific deletion of FUNDC1, which disrupts MAM formation in endothelial cells, lowers VEGFR2 expression and reduces tube formation, spheroid-sprouting, and functional blood vessel formation in vitro and in vivo. Conversely, increased MAM formation using MAM linkers mimics the effects of VEGF and promotes endothelial angiogenesis. Mechanistically, increased MAMs formation led to increased levels of Ca2+ in cytosol, promoted the phosphorylation of serum response factor (SRF) and enhanced the binding of SRF to VEGFR2 promoter, resulting in increased VEGFR2 production, with consequent angiogenesis. Moreover, blocking FUNDC1-related MAM formation with a cell-penetrating inhibitory peptide significantly suppresses the expressions of downstream angiogenic genes and inhibits tumor angiogenesis. We conclude that decreased MAMs formation by silencing FUNDC1 can inhibit angiogenesis by decreasing VEGFR2 expression, and targeting FUNDC1-dependent MAMs might be a promising approach for treating human disorders characterized by defective angiogenesis.

Protein-ligand interaction-guided discovery of novel VEGFR-2 inhibitors.

As an effective target in abnormal angiogenesis-related tumor treatment, VEGFR-2 has small-molecule inhibitors of various scaffolds being approved for treating diseases such as renal carcinoma, non-small cell lung cancer, etc. However, endogenous and acquired drug resistance are still considered to be the main contributors for the failure of VEGFR-2 clinical candidates. Therefore, development of novel VEGFR-2 inhibitors is still urgently needed in the market but also challenging. In this work, residues including Asp1046, Ile1025, HIS1026, Cys919 and Lys868 were identified as the most important residues for Hbonded interaction, while His1026, Asp1046, Glu885, Ile1025 and Leu840 exhibited critical role for the nonbonded interactions through a comprehensive analysis of protein-ligand interactions, which plays critical roles in the binding of compounds and targets. Guided by the analysis of binding interactions, a total of 10 novel VEGFR-2 inhibitors based on N-methyl-4-oxo-N-propyl-1,4-dihydroquinoline-2-carboxamide scaffold were discovered through fragment-based drug design and structure-based virtual screening, which expands the chemical space of current VEGFR-2 inhibitors. Biological activity evaluation showed that even though the enzymatic activity of these compounds against VEGFR-2 were inferior to that of the positive controls sorafenib and motesanib, compound I-10 showed moderate HepG2 cell inhibitory activity with an IC50 value of 33.65 µM and eight compounds exhibited moderate or higher HUVEC inhibitory activity in the range of 19.54-57.98 µM compared to the controls. Particularly, the HUVEC inhibitory activity of compound I-6 (IC50 = 19.54 µM) outperformed motesanib and can be used as starting points for further optimization and development for cancer treatment.Communicated by Ramaswamy H. Sarma.

Suppression of angiogenesis and tumor growth by recombinant T4 phages displaying extracellular domain of vascular endothelial growth factor receptor 2.

Tumor growth, invasion and metastasis are dependent on angiogenesis. The Vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) signaling pathway plays a pivotal role in tumor angiogenesis and therefore represents a reasonable target for anti-angiogenesis/anti-tumor therapy. In the present study, we generated T4 recombinant phages expressing the extracellular domain of VEGFR2 (T4-VEGFR2) and investigated their anti-angiogenic activity. The T4-VEGFR2 phages were able to bind to VEGF specifically and inhibit VEGF-mediated phosphorylation of VEGFR2 and its downstream kinases such as extracellular signal-regulated kinase (ERK) and p38 mitogen activated protein kinase (MAPK). The in vitro experiments showed that the T4-VEGFR2 phages could inhibit VEGF-stimulated cell proliferation and migration of endothelial cells. Finally, administration of T4-VEGFR2 phages was able to suppress tumor growth and decrease microvascular density in murine models of Lewis lung carcinoma and colon carcinoma, and prolong the survival of tumor bearing mice. In conclusion, this study reveals that the recombinant T4-VEGFR2 phages generated using T4-based phage display system can inhibit VEGF-mediated tumor angiogenesis and the T4 phage display technology can therefore be used for the development of novel anti-cancer strategies.

Suppression of Allograft Rejection with Soluble VEGF Receptor 2 Chimeric Protein in a Mouse Model of Corneal Transplantation.

When a transparent cornea becomes opaque due to infectious diseases, trauma, or ophthalmic surgery, the impaired cornea is replaced with a donor cornea to improve visual function. In this corneal transplantation, the graft survival rate is comparatively high, partly because of lacking vascular and lymphatic vessel in cornea. However, the transplanted corneas sometimes become opaque if allograft rejection occurs. Suppression of allograft rejection is critical for favorable outcomes of corneal transplantation. The essential effects of endogenous monomeric soluble vascular endothelial growth factor receptors (VEGFRs) 1 and 2 have been reported in corneal angiogenesis and lymphangiogenesis. This study investigated the effects of dimeric soluble VEGFR2/Fc chimera protein on corneal allograft rejection for future clinical application. Allogeneic full-thickness corneal transplantation was performed in C57BL/6 to BALB/c mice. The recipients were treated by intrastromal injection of soluble VEGFR1/Fc chimera (sR1/Fc group), soluble VEGFR2/Fc chimera (sR2/Fc group), or human IgG1/Fc protein (IgG/Fc group) at 0, 7, and 14 days after surgery. Both hemangiogenesis and lymphangiogenesis were significantly suppressed in the corneas of the sR2/Fc group compared with the IgG/Fc group. All grafts failed due to corneal wound rupture in the sR1/Fc group. In the sR2/Fc group, respective donor-derived MHC class II(+)/CD11c(+) cells and CD11b-positive macrophage infiltration were reduced in the DLNs and the corneas showing a negative delayed-type hypersensitivity, compared with the IgG/Fc group. Our findings demonstrate that soluble VEGFR2/Fc chimera protein efficiently suppresses corneal allo-rejection, while reducing hemangiogenesis and lymhangiogenesis, and immune-competent cell-trafficking and may be a powerful tool for corneal allograft survival.

Lenvatinib in combination with golvatinib overcomes hepatocyte growth factor pathway-induced resistance to vascular endothelial growth factor receptor inhibitor.

Vascular endothelial growth factor receptor (VEGFR) inhibitors are approved for the treatment of several tumor types; however, some tumors show intrinsic resistance to VEGFR inhibitors, and some patients develop acquired resistance to these inhibitors. Therefore, a strategy to overcome VEGFR inhibitor resistance is urgently required. Recent reports suggest that activation of the hepatocyte growth factor (HGF) pathway through its cognate receptor, Met, contributes to VEGFR inhibitor resistance. Here, we explored the effect of the HGF/Met signaling pathway and its inhibitors on resistance to lenvatinib, a VEGFR inhibitor. In in vitro experiments, addition of VEGF plus HGF enhanced cell growth and tube formation of HUVECs when compared with stimulation by either factor alone. Lenvatinib potently inhibited the growth of HUVECs induced by VEGF alone, but cells induced by VEGF plus HGF showed lenvatinib resistance. This HGF-induced resistance was cancelled when the Met inhibitor, golvatinib, was added with lenvatinib. Conditioned medium from tumor cells producing high amounts of HGF also conferred resistance to inhibition by lenvatinib. In s.c. xenograft models based on various tumor cell lines with high HGF expression, treatment with lenvatinib alone showed weak antitumor effects, but treatment with lenvatinib plus golvatinib showed synergistic antitumor effects, accompanied by decreased tumor vessel density. These results suggest that HGF from tumor cells confers resistance to tumor endothelial cells against VEGFR inhibitors, and that combination therapy using VEGFR inhibitors with Met inhibitors may be effective for overcoming resistance to VEGFR inhibitors. Further evaluation in clinical trials is warranted.

Effects of vascular endothelial growth factor on survival of surgical flaps: a review of experimental studies.

Partial or complete necrosis of skin flaps remains a significant problem in plastic and reconstructive surgery. Growth factors have shown promise in improving flap survival through increased angiogenesis and blood supply to the flap. Vascular endothelial growth factor (VEGF) is the most widely investigated and successful one. But the mechanisms of the effects are still not very clear. In the course of a series of experiments, we indicated that tissue survival of surgical flaps could be improved by both preoperative (sustained phase effect) and intraoperative (acute phase effect) application of VEGF. We reviewed both experimental and clinical investigations on the use of VEGF with surgical flaps to summarize the evidence of both phases of VEGF activity in promotion of flaps survival in detail. With the combinations of acute and sustained phases of effects, VEGF protein and gene, VEGF morphologic actions, and VEGF histochemical modulations suggest a pattern of VEGF activity that can be superimposed on classic descriptive mechanisms of tissue survival of flaps.

Periplasmic expression optimization of VEGFR2 D3 adopting response surface methodology: antiangiogenic activity study.

Vascular endothelial growth factor (VEGF) is one of the most significant mediators of angiogenesis, which interacts with a specific membrane receptor: VEGF receptor 2 (VEGFR2). Studies elsewhere have shown that, a VEGF-blocker can regulate several vital processes of tumor promotion. However, there is no literature evidence of investigation on antiangiogenic ability of single domain 3 of VEGFR-2 (VEGFR2 D3), as the key domain in signal transduction of VEGF. In this article, we aimed at developing an efficient method for producing soluble form of this receptor as therapeutic applications. The optimization of the production of soluble VEGFR2 D3 in Escherichia coli was firstly done by testing the periplasmic expression in different expression systems using three osmotic shock methods. To enhance the yield, vital factors were selected from nine factors by Plackett-Burman design and the level of each viral factor was optimized via a response surface methodology based central composite design. After purification and identification of the protein, the bioactivity assays: quantitative ELISA, VEGF-induced proliferation and in vivo chick chorioallantoic membrane assay were employed in our study. The outcome showed that, E. coli Rosetta-gami (DE3)/pET22b-VEGFR2 D3 was the most effective expression system. Furthermore, the inducing time, peptone and glycerol concentration affected the periplasmic expression of VEGFR2 D3 significantly. The corresponding level was also optimized. The bioactivity assay studies showed VEGFR2 D3 could suppress both VEGF stimulated cell proliferation in vitro and neovascularization in vivo. We have therefore provided a novel antiangiogenic drug candidate relating to VEGF-VEGFR2 pathway.

Cerebral endothelial derived vascular endothelial growth factor promotes the migration but not the proliferation of oligodendrocyte precursor cells in vitro.

In gray matter, cerebral endothelium is known to provide trophic support for neighboring cells such as neurons. However, signaling from cerebral endothelium to white matter cells remains to be elucidated. Here, we show that vascular endothelial growth factor (VEGF-A) secreted from cerebral endothelial cells promotes the migration but not the proliferation of oligodendrocyte precursor cells (OPCs). Cultured OPCs were obtained from newborn rat cortex, and treatment with conditioned culture media of cerebral endothelial cells increased the OPC proliferation and migration. Importantly, co-treatment with anti-neutralizing antibody for Flk-1 (VEGF-receptor2) inhibited OPC movement but did not affect OPC propagation. Western blot and flow cytometry analyses confirmed that our cultured cerebral endothelial cells produced VEGF-A and our cultured OPCs expressed Flk-1. Taken together, our current data suggest that cerebral endothelium is supportive for oligodendrocyte lineage cells and VEGF-A may participate in the endothelium-OPC cell-cell signaling. This phenomenon may be important for white matter homeostasis.

The endogenous soluble VEGF receptor-2 isoform suppresses lymph node metastasis in a mouse immunocompetent mammary cancer model.

BACKGROUND: Cancer metastasis contributes significantly to cancer mortality and is facilitated by lymphangiogenesis and angiogenesis. A new splicing variant, endogenous soluble vascular endothelial growth factor receptor-2 (esVEGFR-2) that we recently identified is an endogenous selective inhibitor of lymphangiogenesis. To evaluate the antimetastatic potential of esVEGFR-2, gene therapy with vector expressing esVEGFR-2 (pesVEGFR-2) or endostatin (pEndo) as a positive control was conducted on murine metastatic mammary cancer. METHODS: Syngeneic inoculated metastatic mammary cancers received direct intratumoral injection of pesVEGFR-2, pEndo or pVec as control, once a week for six weeks. In vivo gene electrotransfer was performed on the tumors after each injection. RESULTS: Deaths from metastasis were much lower in the pesVEGFR-2 and pEndo groups than in those of the pVec. Tumor volume was significantly lower in the pesVEGFR-2 and the pEndo groups throughout the study. Multiplicity of lymph node and lung metastatic nodules was significantly suppressed in the pesVEGFR-2 and pEndo groups. Moreover, the total number of overall metastasis including the other organs was also decreased in these groups. However, pesVEGFR-2 was not able to decrease the number of lungs, ovaries, kidneys and adrenals with metastasis as counted by unilateral or bilateral metastasis. The number of CD34+/Lyve-1⁻ blood microvessels was significantly decreased in the pEndo group, while the number of CD34⁻/Lyve-1+ lymphatic vessels was significantly decreased in the pesVEGFR-2 and pEndo groups. In addition, a significant reduction in the number of dilated lymphatic vessels containing intraluminal cancer cells was observed in the pesVEGFR-2 and pEndo groups. Levels of apoptosis were significantly increased in the pEndo group, whereas the rates of cell proliferation were significantly decreased in the pesVEGFR-2 and pEndo groups. CONCLUSIONS: Our data demonstrate that esVEGFR-2 can inhibit mainly lymph node metastasis. The antimetastatic activity of esVEGFR-2 may be of high clinical significance in the treatment of metastatic breast cancer because lymph node involvement is a most important prognostic factor in cancer patients.

Role of c-Cbl-dependent regulation of phospholipase Cgamma1 activation in experimental choroidal neovascularization.

PURPOSE: Activation of phospholipase Cγ1 (PLCγ1) by vascular endothelial growth factor receptor (VEGFR)-2 is necessary for proliferation and tube formation of endothelial cells in vitro. Previous work has demonstrated that Casitas B-lineage lymphoma (c-Cbl) promotes ubiquitination of PLCγ1 and suppression of its tyrosine phosphorylation. This study was designed to evaluate the importance of PLCγ1 and c-Cbl in experimental choroidal neovascularization (CNV). METHODS: The role of PLCγ1 was studied in three models of angiogenesis: the endothelial cell culture system, the chorioallantoic membrane (CAM) assay, and the laser-induced CNV model. Endothelial cells were analyzed for the role of PLCγ1 in promoting tube formation. CAMs were incubated with pharmacologic agents that either inhibit or stimulate PLCγ1. CNV was induced in wild-type and c-Cbl-knockout mice, and the progression of CNV was evaluated by fluorescein angiography. RESULTS: Activation of PLCγ1 was necessary for tube formation of endothelial cells. PLCγ1 stimulation increased the growth of blood vessels and conversely, PLCγ1 inhibition decreased the growth of blood vessels in the CAM model. CNV lesions in the c-Cbl-knockout mice were significantly greater in number, more confluent, and increased in size with time, compared with those in the control wild-type mice. CONCLUSIONS: The data show that PLCγ1 plays an important role in angiogenesis. Loss of c-Cbl results in enhanced CNV in the eye. The study also shows that c-Cbl plays an important role in ocular angiogenesis, suggesting that modulation of c-Cbl activity or inhibition of PLCγ1 would be a compelling target for antiangiogenesis therapy.