血管内皮生长因子-C促进淋巴管内皮细胞的增殖、迁移和F-肌动蛋白重组

目的 研究血管内皮生长因子-C(VEGF-C)对于淋巴管内皮细胞增殖和迁移的作用，探讨VEGF-C促进淋巴管新生的机制。方法 从狗的胸导管分离和培养淋巴管内皮细胞。标记内皮细胞的VEGFR-3和F-肌动蛋白，在荧光显微镜和共聚焦激光扫描显微镜下观察。用VEGF-C刺激后，计数增殖细胞和迁移细胞，测量细胞迁移距离，并与bFGF和VEGF的作用进行比较。结果 淋巴管内皮细胞表达VEGFR-3，静脉内皮细胞为阴性。bFGF和VEGF-C促进淋巴管内皮细胞的增殖，VEGF-C的作用比bFGF强。与对照组相比，bFGF、VEGF和VEGF-C组引起迁移细胞的数目增多和迁移距离增大，VEGF-C的作用最强。在VEGF-C组的迁移细胞，F-肌动蛋白和应力纤维明显增多。结论 淋巴管内皮细胞特异性表达VEGFR-3，VEGF-C促进淋巴管内皮细胞的增殖和迁移，引起F-肌动蛋白的重组和应力纤维形成。     

重组梅毒螺旋体蛋白Tp47通过诱导uPA增加血管内皮细胞通透性

目的探讨重组梅毒螺旋体蛋白Tp47(rTpp47)对单核-巨噬细胞系THP-1合成尿激酶型纤溶酶原激活物(uPA)的调控及其对人脐静脉/血管内皮细胞(HUVECs)通透性的影响。方法用rTpp47刺激THP-1细胞24 h后,分别收集细胞培养上清和THP-1细胞,用ELISA和Western blot检测THP-1细胞表达的uPA含量;用THP-1细胞培养上清刺激人单层血管内皮细胞后,使用FITC-葡聚糖评价单层内皮细胞通透性的变化,用Western blot检测uPA对HUVECs细胞紧密连接蛋白claudin-5表达的影响以及PKC信号通路是否参与rTpp47诱导的THP-1细胞表达uPA。结果重组蛋白rTpp47刺激THP-1细胞合成和分泌的uPA显著高于对照组(P<0.05,P<0.001);用rTpp47与THP-1细胞共培养24 h后收集的细胞培养上清刺激单层血管内皮细胞12和24 h,实验组血管内皮细胞相对通透性显著高于对照组(P<0.05,P<0.000 1);uPA活性抑制剂阿米洛利(amiloride)抑制了rTpp47刺激THP-1细胞分泌...     

血管内皮生长因子C及血管内皮生长因子受体3在人直肠腺癌中的表达及其意义

目的:检测血管内皮生长因子C(VEGF-C)及血管内皮生长因子受体3(VEGFR-3)在人直肠癌组织和淋巴结中的表达,探讨VEGF-C在人直肠癌发生、发展和淋巴结转移中的作用.方法:选用31例手术切除并经病理切片确诊为直肠腺癌的癌组织石蜡标本,采用免疫组织化学方法检测VEGF-C及VEGFR-3在癌组织和淋巴结内的表达.结果:在31例直肠腺癌组织的癌细胞质中,VEGF-C显色阳性者54.8%;VEGFR-3显色阳性者64.5%;在14例淋巴结中,VEGF-C显色阳性者71.4%;VEGFR-3显色阳性者64.3%.结论:VEGF-C和VEGFR-3在直肠癌组织和淋巴结中均有较高表达,VEGF-C通过与VEGFR-3结合,促使淋巴管内皮细胞增殖、迁移并形成新的淋巴管,导致癌细胞转移.     

VEGF及其受体的生物学特性

血管内皮生长因子(Vascular endothelial growth factor,VEGF)及其受体(VEGFR1-VEGFR3)在血管生成中占有重要作用,VEGF有五个成员:VEGF-A、VEGF-B、VEGF-C、VEGFD、以及胎盘生长因子(PlGF);三种受体:VEGFR1-VEGFR3。VEGF-A主要结合在VEGFR-1和VEGFR-2,VEGF-B和PlGF只结合在VEFGR-1上,VEGF-C和VEGF-D只结合在VEGFR-3上。不同的受体在不同的细胞上表达不一致,VEGFR-1主要表达在造血干细胞上;VEGFR-2主要表达在血管内皮细胞上;VEG-FR-3主要表达在淋巴内皮细胞上。VEGF的表达受到低氧转录因子HIF-1的调控,HIF-1是具有PAS环状结构的异二聚体,有三个亚单位:HIF-1α、HIF-2α、HIF-1β,HIF-1蛋白的稳定与降解受上游脯氨酰-4-羟化酶(PHDs)以及抑制因子FIH的调节。VEGF诱导肿瘤血管生成,促进肿瘤的播散、转移。拮抗VEGF的表达则成为抑制肿瘤血管生成的重要策略。     

血管内皮生长因子C及其受体3在人恶性黑色素瘤组织内的表达及意义

目的 观察人恶性黑色素瘤组织内血管内皮生长因子C(VEGF-C)及其受体3(VEGFR-3)的表达,探讨VEGF-C和VEGFR-3在恶性黑色素瘤淋巴管生成及淋巴道转移中的作用.方法 取人恶性黑色素瘤组织48例(石蜡标本30例,术后新鲜组织18例),应用免疫组织化学和RT-PCR技术,观察VEGF-C和VEGFR-3蛋白及mRNA在恶性黑色素瘤组织内的表达情况.以淋巴管内皮透明质酸受体(LYVE-1)标记淋巴管,计数恶性黑色素瘤组织淋巴管数密度.结果 VEGF-C和VEGFR-3蛋白主要表达于恶性黑色素瘤细胞胞浆内,在肿瘤周围的血管和淋巴管内皮上也可见VEGFR-3蛋白表达,VEGF-C和VEGFR-3蛋白在淋巴结转移组恶性黑色素瘤组织内的表达水平明显高于无淋巴结转移组(P<0.05).在18例新鲜恶性黑色素瘤中,淋巴结转移组VEGF-C和VEGFR-3mRNA的表达明显高于无淋巴结转移组(P<0.01).LYVE-1表达于肿瘤间质内的淋巴管内皮细胞,淋巴结转移组恶性黑色素瘤组织中的淋巴管数密度(LMVD)为9.845±2.454,无淋巴结转移组恶性黑色素瘤组织中的淋巴管数密度为6.534±2.193,淋巴结转移组恶性黑色素瘤组织内的淋巴管数密度明显高于无淋巴结转移组(P<0.01).结论恶性黑色素瘤组织内VEGF-C表达明显增高,并通过上调其受体VEGFR-3的表达促进恶性黑色素瘤组织内淋巴管的生成,从而促进恶性黑色素瘤的淋巴道转移.     

细胞因子对淋巴管内皮祖细胞的趋化和动员作用

目的 研究血管内皮生长因子C(VEGF-C)、基质细胞衍生因子-1(SDF-1)、单核细胞趋化蛋白-1(MCP-1)和粒细胞集落刺激因子(G-CSF)对CD34 /CD133 /VEGFR-3 淋巴管内皮祖细胞(LEPCs)的趋化和动员作用.方法 用Percoll非连续密度梯度离心法分离狗外周血单个核细胞,再用流式细胞术分选VEGFR-3 LEPCs,激光扫描共焦显微镜下观察细胞特征性标志物CD34和CD133的表达.通过跨膜迁移实验观察VEGF-C、SDF-1、MCP-1和G-CSF对LEPCs的趋化作用,并用扫描电镜观察迁移细胞的形态特征.在大鼠皮下分别注射VEGF-C、SDF-1、MCP-1和C-CSF,用流式细胞术检测外周血单个核细胞中LEPCs数目,同时用全自动血样分析仪计数白细胞.结果 与对照组相比,VEGF-C、SDF-1、MCP-1和G-CSF组跨膜迁移细胞的百分率增大,用VEGFR-3和CXCR-4阻断抗体处理后VEGF-C和SDF-1的趋化迁移作用明显降低.注射VEGF-C、SDF-1、MCP-1和G-CSF后,大鼠外周血中LEPCs的数量明显增多.未见白细胞显著增多.结论 VEGF-C、SDF-1、MCP-1和G-CSF对LEPCs有趋化迁移和动员作用,VEGF-C/VEGFR-3和SDF-1/CXCR-4信号途径在LEPCs趋化迁移方面起着重要调控作用.     

血管内皮生长因子C及其受体在MNNG诱发的大鼠大肠癌细胞及淋巴管的表达

目的 观察大鼠大肠癌组织内血管内皮生长因子-C(VEGF-C)及其受体3(VEGFR-3)的表达情况,探讨VEGF-C及其受体VEGFR-3在肿瘤淋巴转移中的作用.方法 采用甲基硝基亚硝基胍(MNNG)诱发的大鼠大肠癌模型,应用免疫组织化学(SABC法)技术检测29例大鼠原发性大肠癌组织中VEGF-C及VEGFR-3蛋白,观察VEGF-C及VEGFR-3在大肠癌组织内的表达.结果 正常大肠组织内未见VEGF-C阳性表达,但可见淋巴管内皮细胞VEGFR-3阳性表达.在大肠癌组织内,VEGF-C蛋白表达于癌细胞,早期和中晚期癌的阳性表达率分别是75%和100%,(P＜0.05).VEGFR-3主要表达于淋巴管内皮细胞,早期和中晚期癌组织内淋巴管的阳性表达率分别是58.33%和94.12%(P＜0.05).结论 大鼠大肠癌VEGF-C的表达与肿瘤进展有关,推测VEGF-C通过受体VEGFR-3诱导淋巴管生成:VEGFR-3在淋巴管的阳性表达均随肿瘤进展增高,可能与大肠癌淋巴转移有关.     

IL-33诱导的THP-1细胞对胃癌细胞增殖、迁移和侵袭的影响

目的探讨白介素33(interleukin 33,IL-33)对单核细胞THP-1的诱导分化作用以及IL-33诱导分化的THP-1对胃癌SGC7901细胞增殖、迁移和侵袭的影响。方法 IL-33刺激THP-1细胞72 h后流式细胞术检测M2巨噬细胞表面分子CD163及CD209的表达;ELISA检测细胞因子IL-10、IL-12、TGF-β、TNF-α的蛋白表达;qRT-PCR检测IL-10、IL-12、TGF-β、TNF-α的mRNA表达。克隆形成实验、细胞迁移侵袭实验检测IL-33刺激后的THP-1细胞与SGC7901共培养对SGC7901细胞增殖、迁移和侵袭的影响;Western blot检测共培养后SGC7901细胞上皮间质转化(epithelial mesenchymal transition,EMT)相关蛋白E-cadherin、Vemintin以及Snail的表达。裸鼠成瘤实验检测TAM对体内肿瘤生长的影响。结果 IL-33诱导THP-1细胞表型向M2TAM方向分化;IL-33刺激THP-1促进了SGC7901细胞增殖、迁移和侵袭能力;Western blot检测结果显示,经IL-33诱导的THP-1抑制SGC7901细胞E-cadherin的表达,促进Vemintin和Snail的表达,说明IL-33诱导分化的THP-1细胞促进SGC7901细胞发生EMT。IL-33刺激后的THP-1促进SGC7901细胞在裸鼠体内肿瘤的生长。结论 IL-33可以诱导THP-1发生M2型TAM的分化,分化后的TAM通过EMT机制促进胃癌SGC7901细胞的增殖、迁移和侵袭。     

血管内皮生长因子受体-1促进肝癌细胞侵袭和转移的初步研究

目的 检测不同转移潜能的肝癌细胞中有无血管内皮生长因子受体-1(VEGFR-1)及其配体(VEGF)的表达以探讨VEGFR-1在肝癌侵袭转移中的作用.方法 分别用RT-PCR、ELISA和/或Western blot法检测四种肝癌细胞株MHCC97-H、MHCC97-L、SMMC 7721和HepG 2有无VEGFR-1 mRNA和蛋白表达,用VEGFR-1的特异性配体VEGF-B处理MHCC97-H细胞以研究VEGFR-1活化对肝癌细胞迁移、侵袭和增殖等的影响.结果 MHCC97-H、MHCC97-L和SMMC 7721有VEGFR-1 mRNA和蛋白表达,但4种肝癌细胞都有VEGFR-1的配体VEGF-A和VEGF-B的表达;VEGFR-1活化能促进肝癌细胞MHCC97-H侵袭和迁移;VEGFR-1依赖的侵袭和迁移能被VEGFR-1的中和抗体18F1阻断,VEGFR-1活化不能促进细胞增殖和存活.结论 VEGFR-1及其配体的表达与肝癌细胞的侵袭转移有关,肝癌中的VEGF过表达可以自分泌的方式激活表达VEGFR-1的肝癌细胞,VEGFR-1及其配体可能是防治原发性肝癌侵袭转移的新靶点.     

血管内皮生长因子C的研究进展

血管内皮生长因子C(VEGF-C)是一种特异性血管、淋巴管内皮细胞调节因子,其结构与VEGF具有同源性。VEGF-C通过受体VEGFR-2和VEGFR-3发挥作用,其mRNA的表达具有一定的组织特点,并受多种因素的调节。VEGF-C对于胚胎发育、细胞分化、活体内外血管、淋巴管内皮细胞均有重要的调节作用。     

Localisation of members of the vascular endothelial growth factor (VEGF) family and their receptors in human atherosclerotic arteries

BACKGROUND: Vascular endothelial growth factor (VEGF) mediates endothelial cell mitogenesis and enhances vascular permeability. The existence of single or multiple VEGF isoforms and receptors suggests that these proteins may have overlapping but distinct functions, which may be reflected in their cell expression and distribution. METHODS: The localisation of VEGFs A-C and their receptors (VEGFRs 1-3, respectively) in 30 fresh human atherosclerotic arteries, 15 normal uterine arteries, and 15 saphenous veins using immunohistochemistry and western blotting. RESULTS: Saphenous veins showed no staining for VEGF-B or VEGFR-2. Smooth muscle cells (SMCs) showed the strongest staining for VEGF-A, VEGF-B, VEGFR-1, and VEGFR-2 in all specimens. Conversely, VEGFR-3 and VEGF-C were predominantly localised to the endothelial vasa vasorum in normal arteries, whereas medial SMCs showed the strongest staining in atherosclerotic arteries. Western blotting showed variations in VEGF protein localisation, with lower amounts of VEGF-B and VEGF-C in saphenous veins, compared with arterial tissue. Amounts of VEGF-C were lower than those of VEGF-A and VEGF-B in all specimens. CONCLUSION: This study provides direct evidence of the presence of VEGF proteins and receptors in human physiology and pathology, with variations in both the amounts of VEGF proteins expressed and their cellular distribution in normal arteries compared with atherosclerotic arteries. The presence of VEGFs A-C and their receptors in normal arterial tissue implies that VEGF functions may extend beyond endothelial cell proliferation. Reduced VEGFR-2 staining in atherosclerotic arteries may have implications for the atherosclerosis process and the development of vascular disease and its complications.     

Vascular endothelial growth factor-C, a potential paracrine regulator of glomerular permeability, increases glomerular endothelial cell monolayer integrity and intracellular calcium

We have previously reported expression of vascular endothelial growth factor (VEGF)-A and -C in glomerular podocytes and actions of VEGF-A on glomerular endothelial cells (GEnC) that express VEGF receptor-2 (VEGFR-2). Here we define VEGFR-3 expression in GEnC and investigate the effects of the ligand VEGF-C. Renal cortex and cultured GEnC were examined by microscopy, and both cell and glomerular lysates were assessed by Western blotting. VEGF-C effects on trans-endothelial electrical resistance and albumin flux across GEnC monolayers were measured. The effects of VEGF-C156S, a VEGFR-3-specific agonist, and VEGF-A were also studied. VEGF-C effects on intracellular calcium ([Ca²⁺]_i) were measured using a fluorescence technique, receptor phosphorylation was examined by immunoprecipitation assays, and phosphorylation of myosin light chain-2 and VE-cadherin was assessed by blotting with phospho-specific antibodies. GEnC expressed VEGFR-3 in tissue sections and culture, and VEGF-C increased trans-endothelial electrical resistance in a dose-dependent manner with a maximal effect at 120 minutes of 6.8 Ω whereas VEGF-C156S had no effect. VEGF-C reduced labeled albumin flux by 32.8%. VEGF-C and VEGF-A increased [Ca²⁺]_i by 15% and 39%, respectively. VEGF-C phosphorylated VEGFR-2 but not VEGFR-3, myosin light chain-2, or VE-cadherin. VEGF-C increased GEnC monolayer integrity and increased [Ca²⁺]_i, which may be related to VEGF-C-S particular receptor binding and phosphorylation induction characteristics. These observations suggest that podocytes direct GEnC behavior through both VEGF-C and VEGF-A.     

Release and complex formation of soluble VEGFR-1 from endothelial cells and biological fluids

One of the key molecules promoting angiogenesis is the endothelial cell-specific mitogen, vascular endothelial growth factor (VEGF or VEGF-A), which acts through two high-affinity receptor tyrosine kinases (VEGFR), VEGFR-1 (or Flt-1) and VEGFR-2 (or KDR/Flk-1). It was shown before that a soluble variant of VEGFR-1 (sVEGFR-1) can be generated by differential splicing of the flt-1 mRNA. This soluble receptor is an antagonist to VEGF action, reducing the level of free, active VEGF-A, and therefore, plays a pivotal role in the generation of vascular diseases like pre-eclampsia or intra-uterine growth retardation. Here we show that sVEGFR-1 is produced by cultured human microvascular and macrovascular endothelial cells and a human melanoma cell line. The soluble receptor is mainly complexed with ligands; only 5-10% remains detectable as free, uncomplexed receptor protein. Furthermore, we show the time course of total and free sVEGFR-1 release together with its putative ligands, VEGF-A and placenta growth factor (PIGF), from macrovascular endothelial cells. The release of sVEGFR-1 was quantitatively measured in two different ELISA types. The release of sVEGFR-1 was strongly enhanced by phorbol-ester (PMA); the cells produced up to 22 ng/ml of sVEGFR-1 after 48 hours. The expression of VEGF-A and PIGF was moderately influenced by PMA. We also show a hypoxia-induced increase of sVEGFR-1 expression in cells cultured from placenta, a tissue that has a high flt-1 gene expression. Moreover, we demonstrate that sVEGFR-1 in amniotic fluids acts as a sink for exogenous VEGF165 and PIGF-2. Here, for the first time, to what extent recombinant ligands have to be added to compensate for the sink function of amniotic fluids was analyzed. In conclusion, human endothelial cells produce high levels of sVEGFR-1, which influences the availability of VEGF-A or related ligands. Therefore, sVEGFR-1 may reduce the ligand binding to transmembrane receptors and interfere with their signal transduction.     

Vascular endothelial growth factor ligands and receptors that regulate human cytotrophoblast survival are dysregulated in severe preeclampsia and hemolysis, elevated liver enzymes, and low platelets syndrome

Human placental development combines elements of tumorigenesis and vasculogenesis. The organ's specialized epithelial cells, termed cytotrophoblasts, invade the uterus where they reside in the interstitial compartment. They also line uterine arteries and veins. During invasion, ectodermally derived cytotrophoblasts undergo pseudovasculogenesis, switching their adhesion molecule repertoire to mimic that of vascular cells. Failures in this transformation accompany the pregnancy complication preeclampsia. Here, we used a combination of in situ and in vitro analyses to characterize the cell's expression of vascular endothelial growth factor (VEGF) family ligands and receptors, key regulators of conventional vasculogenesis and angiogenesis. Cytotrophoblast differentiation and invasion during the first and second trimesters of pregnancy were associated with down-regulation of VEGF receptor (VEGFR)-2. Invasive cytotrophoblasts in early gestation expressed VEGF-A, VEGF-C, placental growth factor (PlGF), VEGFR-1, and VEGFR-3 and, at term, VEGF-A, PlGF, and VEGFR-1. In vitro the cells incorporated VEGF-A into the surrounding extracellular matrix; PlGF was secreted. We also found that cytotrophoblasts responded to the VEGF ligands they produced. Blocking ligand binding significantly decreased their expression of integrin alpha1, an adhesion molecule highly expressed by endovascular cytotrophoblasts, and increased apoptosis. In severe preeclampsia and hemolysis, elevated liver enzymes, and low platelets syndrome, immunolocalization on tissue sections showed that cytotrophoblast VEGF-A and VEGFR-1 staining decreased; staining for PlGF was unaffected. Cytotrophoblast secretion of the soluble form of VEGFR-1 in vitro also increased. Together, the results of this study showed that VEGF family members regulate cytotrophoblast survival and that expression of a subset of family members is dysregulated in severe forms of preeclampsia.     

Liver metastases arising from well-differentiated pancreatic endocrine neoplasms demonstrate increased VEGF-C expression.

Pancreatic endocrine neoplasms (PENs) are uncommon, generally well-differentiated neoplasms that demonstrate prominent endocrine differentiation. Although the majority of PENs remain localized, malignant spread may occur via lymphatic or hematogenous routes. Angiogenic growth factors, including the vascular endothelial growth factor (VEGF) family, have been implicated in new vessel growth and hematogenous metastases, although this has not been studied in PENs. We therefore examined 19 primary well-differentiated PENs and 7 liver metastases to determine the expression of VEGF-A and its family member VEGF-C by immunolabeling analysis. VEGF-A immunoreactivity was evident only in scattered cells throughout all lesions. VEGF-C, however, demonstrated low-to-moderate expression in primary PENs by semiquantitative histoscore analysis (factor of labeling intensity by percentage of positive cells), with significantly increased expression in liver metastases (mean histoscore indices: primary PEN, 4.7 versus liver metastases, 9.5; Student's t test; P =.002773). Microvascular density of primary PENs and liver metastases did not appear to linearly correlate with VEGF-C expression. Examination of the VEGF-C-specific receptors VEGFR-2/KDR/Flk-1 and VEGFR-3/Flt-4 demonstrated intense endothelial immunoreactivity for VEGFR-2, as well as VEGFR-2 and -3 expression on the majority of neoplastic cells, suggesting a possible role in autocrine/paracrine neoplastic growth regulation. We postulate that the upregulation of VEGF-C may be involved in PEN progression and metastases, although not via a direct proangiogenic mechanism.     

一氧化氮在VEGF介导的内皮细胞增殖与分泌效应中的作用

目的: 探讨一氧化氮在血管内皮生长因子(VEGF)介导的血管内皮细胞增殖与分泌效应中所起的作用,了解VEGF可能的作用机制。方法:将体外培养的兔主动脉内皮细胞分成对照组、VEGF处理组和VEGF+N-硝基-L-精氨酸甲酯(L-NAME)处理组,采用四氮唑盐WST-1比色法、放免法和酶联免疫双抗体夹心法分别检测吸光值及内皮素-1和Ⅷ因子辅因子水平。结果:VEGF处理组吸光值明显高于VEGF+ L-NAME处理组,且均高于对照组(P＜0.01);VEGF处理组内皮素-1和Ⅷ因子辅因子水平明显低于VEGF+L-NAME处理组,且均低于对照组(P＜0.05和P＜0.01);提示VEGF能促进内皮细胞增殖,抑制内皮细胞分泌内皮素-1和Ⅷ因子辅因子,而L-NAME能部分拮抗VEGF的上述作用。结论:一氧化氮在VEGF促进内皮细胞增殖及抑制内皮细胞分泌内皮素 -1和Ⅷ因子辅因子中起中介作用,VEGF可能部分通过一氧化氮起作用,一氧化氮是VEGF作用机制中的一个重要信号通路。     

Expression of vascular endothelial growth factor-C and its receptor in osteosarcomas

Vascular endothelial growth factor-C (VEGF-C) and its receptor, vascular endothelial growth factor receptor-3 (VEGFR-3), have been implicated as important factors in the formation of lymphatic vessels, but its role in osteosarcomas has not yet been fully investigated. This study aims to define the expression of VEGF-C and VEGFR-3 in primary and metastatic osteosarcomas and their relationship to various clinicopathologic parameters. Thirty-three primary osteosarcomas and two pulmonary metastatic samples were immunostained for VEGF-C and VEGFR-3. In addition, VEGF-C and vascular endothelial growth factor-D (VEGF-D) mRNA expression levels in three different human osteosarcoma cell lines and control fibroblasts were evaluated by real-time quantitative polymerase chain reaction (PCR). Both VEGF-C and VEGFR-3 were expressed mainly in the cytoplasm of the tumor cells. Of the 35 patients with osteosarcoma, 16 patients (45.7%) showed strong positive reaction with VEGF-C. Four cases (11.4%) were negative, and 15 cases (42.9%) showed weak immunoreactivity. For VEGFR-3, 12 patients (34.3%) showed strong positive reaction. Fifteen cases (42.9%) were negative, and eight cases (22.8%) showed weak immunoreactivity. A significant, positive correlation (Rs=0.42, p=0.01) was found between the expression of VEGF-C and VEGFR-3 in osteosarcomas. The expression of VEGF-C was significantly associated with the osteoblastic subtype and high histologic grade in osteosarcomas. However, the expression of VEGF-C showed no significant correlation with the presence of metastasis. Expression of VEGFR-3 was not related to any clinicopathologic features analyzed. Two of the three osteosarcoma cell lines tested showed amplification of VEGF-C mRNA compared with control cells. No amplification of VEGF-D was noted in these cell lines. Our data suggest that VEGF-C and its receptor are expressed in osteosarcomas. Although the level of VEGF-C was high, it does not seem to have a direct influence on tumor metastasis in osteosarcomas.     

Vascular Endothelial Growth Factor Receptor-1 Modulates Vascular Endothelial Growth Factor-Mediated Angiogenesis via Nitric Oxide

The known responses of vascular endothelial growth factor (VEGF) are mediated through VEGF receptor-2 (VEGFR-2/KDR) in endothelial cells. However, it is unknown whether VEGFR-1 (Flt-1) is an inert decoy or a signaling receptor for VEGF during physiological or pathological angiogenesis. Here we report that VEGF-stimulated nitric oxide (NO) release is inhibited by blockade of VEGFR-1 and that VEGFR-1 via NO negatively regulates of VEGFR-2-mediated proliferation and promotes formation of capillary networks in human umbilical vein endothelial cells (HUVECs). Inhibition of VEGFR-1 in a murine Matrigel angiogenesis assay induced large aneurysm-like structures. VEGF-induced capillary growth over 14 days was inhibited by anti-VEGFR-2-blocking antibody as determined by reduced tube length between capillary connections (P < 0.0001) in an in vitro angiogenesis assay. In contrast, loss of VEGFR-1 activity with a neutralizing anti-VEGFR-1 antibody resulted in an increase in the accumulation of endothelial cells (P < 0.0001) and a dramatic decrease in the number of capillary connections that were restored by the addition of NO donor. Porcine aortic endothelial (PAE) cells expressing human VEGFR-1 but not VEGFR-2 plated on growth factor-reduced Matrigel rearranged into tube-like structures that were prevented by anti-VEGFR-1 antibody or a cGMP inhibitor. VEGF stimulated NO release from VEGFR-1- but not VEGFR-2-transfected endothelial cells and placenta growth factor-1 stimulated NO release in HUVECs. Blockade of VEGFR-1 increased VEGF-mediated HUVEC proliferation that was inhibited by NO donors, and potentiated by NO synthase inhibitors. These data indicate that VEGFR-1 is a signaling receptor that promotes endothelial cell differentiation into vascular tubes, in part by limiting VEGFR-2-mediated endothelial cell proliferation via NO, which seems to be a molecular switch for endothelial cell differentiation.