Microvessel density, vascular endothelial growth factor and its receptors Flt-1 and Flk-1/KDR in hepatocellular carcinoma.

Assessment of angiogenesis may yield important information for an effective antiangiogenic treatment for hepatocellular carcinoma (HCC) because HCC is characteristically hypervascular We examined the relationship of microvessel density (MVD), vascular endothelial growth factor (VEGF), and VEGF receptors Flt-1 and Flk-1/KDR in 50 patients with HCC and in 3 hepatoma cell lines. VEGF messenger RNA (mRNA) was overexpressed in 26 tumors (52%), and the 3 VEGF isoforms (121, 165, and 189) were present in high frequencies. Flt-1 mRNA was overexpressed in 34 tumors (68%), with levels significantly increased in HCCs compared with the nontumorous livers. Tumor Flt-1 mRNA significantly correlated with tumor VEGF mRNA levels. Within the group of tumors 8.5 cm or less in diameter, tumors with intrahepatic metastasis in the form of tumor microsatellite formation had significantly higher VEGF mRNA levels. MVD assessed by immunohistochemical analysis with CD34 antibody was inversely related to tumor size. Angiogenesis as assessed by MVD and tumor VEGF expression seems to have a more important role in tumor growth and intrahepatic metastasis in smaller HCCs. The differential up-regulation of Flt-1 suggests that it may have an important role in angiogenesis in HCC.     

Distribution of Flk-1 and Flt-1 receptors in neonatal and adult rat brains

Double-fluorescence staining was combined with confocal laser scanning microscopy to localize fetal liver kinase-1 (Flk-1) and fms-like tyrosine kinase-1 (Flt-1) in the neonatal rat brain. The results showed that Flk-1 and Flt-1 immunostaining was observed in the cells with neuron-specific enolase, a neuronal marker, and with factor VIII (F VIII), an endothelium marker, but not in cells with glial fibrillary acidic protein (GFAP), a glial marker, of brain sections from rats on postnatal day 7 (P7). This indicates that both vascular endothelial growth factor (VEGF) receptors were distributed in the neurons and the vascular endothelium. A regional analysis showed that Flt-1 was distributed most densely in the hippocampus, followed by the retrosplenial agranular cortex and the striatum, and Flk-1 was evenly distributed throughout the brain. In a comparison of the density of immunopositive staining neurons, Flt-1 was much higher than Flk-1 in most of the brain regions. A time-course analysis showed that both Flt-1 and Flk-1 were highly expressed in the cerebral vessel of rats on P1, P7, and P14, and then declined in adults, consistent with the development of angiogenesis in neonates. In the neurons, Flt-1 was highest in the cerebral cortex and hippocampus of P1-P14 rats, and then gradually decreased, whereas Flk-1 abruptly increased and reached its highest level in adults. The results suggest that Flt-1 and Flk-1 are expressed in the neurons with their individual time-dependent manners and regional distribution in the brain. However, the significance of the neuronal distribution of Flt-1 and Flk-1 remains to be determined.     

Design of a variant of vascular endothelial growth factor-A (VEGF-A) antagonizing KDR/Flk-1 and Flt-1

Because of its central role in pathological angiogenesis, vascular endothelial growth factor (VEGF) has become a major target for anti-angiogenic therapies. We report here the construction of a heterodimeric antagonistic VEGF variant (HD-VEGF). In this antagonist, binding domains for the VEGF-receptors KDR/Flk-1 and Flt-1 are present at one pole of the dimer, whereas the other pole carries domain swap mutations, which prevent binding to either receptor. As HD-VEGF can only bind to monomeric receptors, it does not lead to signal transduction. Moreover, it antagonizes VEGF and possibly other members of the VEGF family, which are KDR/Flk-1 and Flt-1 ligands. We show here that HD-VEGF is a potent inhibitor of VEGF-mediated proliferation and tissue factor induction in endothelial cell cultures, requiring only a 20-fold and a 4-fold excess, respectively, to block the activity of wtVEGF completely. A 4-fold excess of HD-VEGF over wtVEGF was also sufficient to abrogate vascular permeability as determined in the Miles assay in vivo. Furthermore, HD-VEGF inhibited fetal bone angiogenesis in an ex vivo assay. Thus, HD-VEGF blocks KDR- and Flt-1-mediated VEGF activities that are crucial in the angiogenic process and is therefore a promising, multipotent compound in the treatment of angiogenesis-related diseases.     

Flt-1、Flk-1在胶原诱导的关节炎小鼠关节组织中的表达

目的研究血管内皮生长因子(VEGF)受体F lt-1、F lk-1在Ⅱ型胶原诱导的关节炎(C IA)形成期的表达,探讨VEGF在类风湿性关节炎发病中的作用。方法于DBA/1 J小鼠皮下注射Ⅱ型胶原制作小鼠关节炎动物模型并进行关节指数评价,用ELISA法和免疫组织化学技术检测关节组织内VEGF及血管性假性血友病因子(vWF)含量,通过RT-PCR,Southern b lotting技术检测关节组织内VEGF及其特异性受体F lt-1、F lk-1mRNA表达。结果VEGF及vWF水平呈平行变化关系,均在关节炎发生后第四天达到最高水平,并与血管新生程度、关节炎严重程度呈正相关。关节组织内VEGF mRNA分别在279bp和304bp扩增片段有特异性表达、其特异性受体F lt-1、F lk-1 mRNA在377bp、402bp扩增片段有特异性表达。结论VEGF-F lt-F lk系统在关节炎形成早期起着重要作用,影响着实验诱导关节炎血管新生及病程。     

Soluble ICAM-1 and VCAM-1 as markers of endothelial activation

Activated endothelium releases the soluble adhesion molecules vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1). Measurement of fluid-phase adhesion molecules is therefore used to quantify endothelial activation, but it is unclear which is the better marker. The aims of the study were to compare the relationships between mRNA, surface and total expression and released VCAM-1 and ICAM-1 in endothelial cell cultures during activation, and to compare human umbilical vein endothelial cells (HUVEC) with the microvascular cell line HMEC-1. sVCAM-1 better represented mRNA and surface expression changes in HUVEC undergoing endotoxin stimulation than did sICAM-1. Very little VCAM-1 was released from endotoxin-stimulated HMEC-1, and sICAM-1 seemed a better activation marker for these cells. During incubation of HUVEC in media with glucose concentrations of 5.6, 10.6 or 20.6 m m , VCAM-1 was released to the media in a dose-dependent way without changes in surface expression. ICAM-1 was not influenced by the glucose concentration. There are situations when VCAM-1 concentrations in the media do not mirror the surface expression on HUVEC in culture, indicating that measurements of soluble adhesion molecules may not necessarily be representative of the conditions on the cell surface. Endothelium from different locations showed varying responses with respect to VCAM-1 and ICAM-1 liberation upon endotoxin stimulation. Thus, both sVCAM-1 and sICAM-1 should be quantified in clinical studies of endothelial activation until their characteristics are better clarified.     

VEGF及其特异性受体Flt-1、Flk-1在CIA小鼠关节组织中的表达与调节

目的：研究血管内皮生长因子（VEGF）及其特异性受体Fit-1、Flk-1在Ⅱ型胶原诱导的关节炎（CIA）形成期的表达与调节，探讨VEGF在类风湿关节炎发病中的作用。方法：于DBA／1J小鼠皮下注射Ⅱ型胶原制作小鼠关节炎动物模型并进行关节炎指数评价，用ELISA法和免疫组织化学技术检测关节组织内VEGF及vWF含量以及通过RT-PCR、Southernblot技术检测关节组织内VEGF及其特异性受体Fit-1、Flk-1mRNA表达。结果：VEGF及vWF呈平行变化关系，均在关节炎发生后第四天达到最高，并与血管新生程度、关节炎严重程度呈正相关。关节组织内VEGFmRNA分别在279bp和304bp扩增片段有特异性表达，其特异性受体Fit-1、Fik-1mRNA在377bp和402bp扩增片段有特异性表达。结论：VEGF-Fit-Flk系统在关节炎形成早期起着重要作用，影响着实验诱导关节炎血管新生及病程。     

Expression of Flt-1 and Flk-1 receptors for vascular endothelial growth factor on tumor cells as a new prognostic criterion for locally advanced breast cancer

We studied expression of Flt-1 and Flk-1 receptors on tumor cells obtained from 83 patients with locally advanced breast cancer after neoadjuvant chemotherapy. The mean period of observations was 32.3 months. The median recurrence-free survival periods for Flt-1⁺ and Flt-1^- patients were 55 and 32 months, respectively (p=0.0064). The overall survival periods for Flt-1^- and Flt-1⁺ patients were 45 and 67.6 months, respectively (p=0.014). The mean recurrence-free survival periods for Flk-1⁺ and Flk-1^- patients were 40.8 and 60.9 months, respectively (p=0.035). Expression of VEGF had no prognostic value. Our results show that overexpression of Flk-1 on breast cancer cells in patients receiving neoadjuvant chemotherapy is associated with a poor prognosis. By contrast, overexpression of Flt-1 improves survival.     

The vascular endothelial growth factor (VEGF) receptor Flt-1 (VEGFR-1) modulates Flk-1 (VEGFR-2) signaling during blood vessel formation

Mice lacking the vascular endothelial growth factor (VEGF) receptor flt-1 (VEGFR-1) die from vascular overgrowth, caused primarily by aberrant endothelial cell division (Kearney JB, Ambler CA, Monaco KA, Johnson N, Rapoport RG, Bautch VL: Vascular endothelial growth factor receptor Flt-1 negatively regulates developmental blood vessel formation by modulating endothelial cell division. Blood 2002, 99:2397-2407). Because a second high-affinity VEGF receptor, flk-1, produces a positive endothelial proliferation signal, it was logical to ask whether flt-1 affects developmental blood vessel formation by modulating signaling through flk-1. Differentiated embryonic stem cell cultures lacking flt-1 (flt-1-/-) had increased flk-1 tyrosine phosphorylation, indicating that flk-1 signaling is up-regulated in the mutant background. The selective flk-1 inhibitor SU5416 partially rescued the flt-1-/- mutant phenotype, and this rescue was accompanied by a decrease in the relative amount of flk-1 tyrosine phosphorylation. Thus reduced flk-1 signal transduction can partially compensate for the lack of flt-1. The flt-1-/- mutant phenotype was also partially rescued by Flt-1/Fc, a truncated flt-1 that binds and sequesters the VEGF ligand. Taken together, these data show that down-regulation of flk-1 signaling by two different strategies partially rescues the developmental vascular overgrowth seen in the absence of flt-1, and they support a model whereby flt-1 modulates the flk-1 signal at an early point in the pathway.     

抑癌基因ING1不同剪接体差异性调节肝癌细胞HepG2生长

生长抑制因子(inhibitor of growth 1,ING1)是通过将人乳腺癌上皮细胞的cDNA与正常上皮细胞cDNA进行消减杂交,然后结合体内选择技术而克隆出的抑癌基因.     

抑癌基因ING1不同剪接体差异性调节肝癌细胞HepG2生长

生长抑制因子(inhibitor of growth 1,ING1)是通过将人乳腺癌上皮细胞的cDNA与正常上皮细胞cDNA进行消减杂交,然后结合体内选择技术而克隆出的抑癌基因.     

Expression of vascular endothelial growth factor receptor Flk-1 in canine mammary tumours

Vascular endothelial growth factor (VEGF) induces endothelial cell proliferation, and the beginning of angiogenesis, by interacting with specific endothelial receptors termed VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1). In this study, Flk-1 expression was evaluated immunohistochemically in 10 benign and 40 malignant canine mammary tumours. There was immunolabelling of endothelial cells located within the neoplastic proliferation and at the infiltrating periphery, and also of neoplastic cells. The number of positive endothelial and neoplastic cells, was higher in malignant than in benign tumours. Moreover, in the malignant tumours, expression of Flk-1 increased from well to less differentiated phenotypes (grade 1-3). The presence of VEGF receptor on neoplastic cells suggests that VEGF has an autocrine function in which neoplastic cells act as both VEGF producers and target cells. Thus, in malignant tumours, VEGF may contribute to neoplastic growth by inducing angiogenesis and by stimulating the proliferation of neoplastic cells.     

Anethole dithiolethione regulates oxidant-induced tyrosine kinase activation in endothelial cells

Interaction between neutrophils and endothelial cells is one of the first steps in the functional response of polymorphonuclear neutrophils (PMN), and is necessary for their migration toward damaged tissues. PMN activation, leading to their adhesion to and migration between endothelial cells, is part of a complex phenomenon that can be altered in pathological situations such as the ischemia-reperfusion syndrome, in which large numbers of PMN are recruited to the tissue and release reactive oxygen species (ROS) near the vessel wall. ROS have been implicated in the pathogenesis of various inflammatory diseases. The increased adhesion of PMN to ROS-stimulated endothelial cells involves an increase in tyrosine phosphorylation of a tyrosine kinase focal adhesion kinase (p125FAK) and several cytoskeleton proteins, including paxillin and p130 cas. We examined the role of glutathione (GSH) in the regulation of this adhesion phenomenon and in the increased tyrosine phosphorylation induced by ROS. For this purpose we used anethole dithiolthione (ADT), which increases the glutathione synthesis by activating gamma-glutamyl-cysteine synthetase. We found that ADT reduced both PMN adhesion to ROS-stimulated human umbilical vein endothelial cells (HUVEC) and tyrosine phosphorylation of p125FAK and paxillin. ADT increased redox status by increasing intracellular GSH content in oxidized cells. These results show that GSH can reverse the effect of oxidation on tyrosine kinase activation and phosphorylation, and thus plays an important role in cell signaling. They also confirm the antioxidant activity of ADT.     

Vascular endothelial growth factor and its receptor, Flt-1, in smokers and non-smokers

Raised levels of plasma vascular endothelial growth factor (VEGF) are found in some cancers, diabetes, and certain other conditions, but levels of its receptor, soluble Flt-1 (sFlt-1), in these diseases have yet to be reported. We hypothesised that smoking would influence levels of these molecules. Consequently, we measured VEGF and sFlt-1 by enzyme-linked immunosorbent assay (ELISA) in plasma from 92 non-smokers and 35 smokers. No difference in VEGF was seen between the groups but, despite considerable overlap, sFlt-1 was significantly lower in smokers (P = 0.027). VEGF and sFlt-1 correlated strongly with each other (P < 0.001). Although VEGF may arise from a number of cell types, including endothelial cells, the primary source of sFlt-1 is thought to be the endothelium; however, neither VEGF nor sFlt-1 correlated with levels of the endothelial cell activation/damage marker soluble thrombomodulin. Our data point to changes in levels of the VEGF receptor, sFlt-1--but not VEGF itself--in smokers, which appears to be unrelated to endothelial cell function.     

Expression of vascular endothelial growth factor (VEGF) and its receptors (VEGF-R1 [Flt-1] and VEGF-R2 [KDR/Flk-1]) in tumorlets and in neuroendocrine cell hyperplasia of the lung

Pulmonary tumorlets and neuroendocrine (NE) cell hyperplasia are part of a continuous spectrum of NE-cell hyperplasia, going from NE hyperplasia to carcinoid. Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen that has been shown to be increased in hypoxic lung. We hypothesized that tumorlets and NE-cell hyperplasia, which occur frequently in this context, were partly responsible for VEGF secretion. Immunohistochemical analysis of VEGF and both VEGF-R1 and VEGF-R2 was performed on paraffin sections of 12 lung tissues containing tumorlets and NE-cell hyperplasia in parallel with a control group of 11 lung specimens. VEGF and its receptor expressions were compared in bronchial epithelial cells and endothelial cells in both groups. VEGF and its receptors were consistently expressed in tumorlets and in NE-cell hyperplasia. When compared with control group lungs, the staining score for VEGF in lung bearing tumorlets was significantly higher in endothelial cells, but was not different in bronchial epithelial cells. VEGF-R1 expression was significantly increased both on bronchial epithelial cells (P = 0.001) and endothelial cells (P = 0.006), and VEGF-R2 expression was significantly increased on endothelial cell (P = 0.044). There was a significant positive correlation between the level of expression of VEGF and VEGF-R1 (P = 0.04) in both control groups and lung bearing tumorlets, but there was no significant correlation between VEGF and VEGF-R2 expression (P = 0.1). We concluded that VEGF is highly expressed in localized NE cell proliferations without potential of malignancy and might participate in local development of fibrosis.     

PKA regulates HMGB1 through activation of IGFBP-3 and SIRT1 in human retinal endothelial cells cultured in high glucose

Objective and Design

Inflammation is a key component of a number of diseases, including diabetic retinopathy. We investigated the cellular pathway by which protein kinase A (PKA) inhibited high mobility group box 1 (HMGB1).

Methods

Primary human retinal endothelial cells (REC) were grown in normal glucose (5 mM) or high glucose (25 mM). Cells in high glucose were treated with exchange protein for cAMP 1 (Epac1) and IGFBP-3 siRNA. Additional cells in high glucose were treated with forskolin, a PKA agonist, and Epac1 siRNA. Some cells were treated with a plasmid for insulin-like growth factor binding protein 3 (IGFBP-3) that does not bind IGF-1. Finally, some REC received Ex527, a sirtuin 1 (SIRT1) antagonist, prior to forskolin treatment. Protein analyses were done for HMGB1, Epac1, IGFBP-3, SIRT1, and PKA.

Results

PKA inhibited cytoplasmic HMGB1, independent of Epac1 actions. PKA activated IGFBP-3 and SIRT1 to inhibit cytoplasmic HMGB1. High glucose inhibited SIRT1 levels and increased cytoplasmic HMGB1 in REC.

Conclusions

PKA requires active IGFBP-3 and SIRT1 to inhibit HMGB1 inflammatory actions in the retina vasculature. Activation of these pathways may offer new targets for therapy development.

     

Vascular endothelial growth factor and its receptor Flk-1 are expressed in the hippocampus following entorhinal deafferentation

Vascular endothelial growth factor (VEGF) has been thought of as a mitogen that promotes proliferation of endothelial cells and as a neurotrophic factor that stimulates neurogenesis and axonal growth in both peripheral and central nervous systems. To investigate the potential involvement of VEGF in the lesion-induced reorganization in the brain, the expression changes of VEGF and its receptor Flk-1 were analyzed in the mouse hippocampus after transections of the entorhinal afferents. In situ hybridization and immunohistochemistry showed the time-dependent expression upregulation of VEGF mRNA and protein in the entorhinally denervated hippocampal stratum lacunosum-moleculare and dentate outer molecular layer, which initiated by 3 days postlesion, reached its maximum at 7-15 days postlesion, still persisted by 30 days postlesion for protein, and recovered to the normal levels at 30 days postlesion for mRNA and at 60 days postlesion for protein. Double labeling of VEGF and glial fibrillary acidic protein revealed that VEGF-expressing cells in the denervated areas were reactive astrocytes. Semi-quantitative RT-PCR analysis showed that VEGF receptor Flk-1 mRNA was also time-dependently upregulated in the deafferented hippocampus with its maximal elevation at 7-15 days postlesion while the Flt-1 mRNA levels remained unchanged at any time point we examined. Immunohistochemistry analysis also displayed the upregulation of Flk-1 protein in the denervated stratum lacunosum-moleculare and outer molecular layer with a time course similar to that of VEGF mRNA upregulation. Flk-1 receptors were found to be expressed not only by reactive astrocytes but also by neurites, which most likely belong to sprouting axons by 7 days postlesion and regrowing dendrites by 15-30 days postlesion. From these data we suggest that the spatiotemporal upregulation of VEGF and Flk-1 in the hippocampus is induced by entorhinal deafferentation and that VEGF may be involved in the structural reorganization in the deafferented hippocampus via directly or indirectly promoting neurite growth.     

The Wilms tumor suppressor WT1 regulates early gonad development by activation of Sf1

In mammals, several genes including the Wilms tumor suppressor gene Wt1, the Lim homeobox gene Lhx9, and the gene encoding steroidogenic factor 1 (Sf1) have been implicated in the development of the indifferent gonad prior to sexual differentiation. Interactions among these genes have not yet been elucidated. Using biochemical and genetic experiments, we demonstrate here that WT1 and LHX9 function as direct activators of the Sf1 gene. Interestingly, only the -KTS form of WT1 is able to bind to and transactivate the Sf1 promoter. This observation is consistent with differential roles for the -KTS and +KTS variants of WT1 which have been postulated on the basis of human disorders such as the Frasier syndrome. Our data suggest a pathway in which the products of the Wt1 and Lhx9 genes activate expression of Sf1 and thus mediate early gonadogenesis.     

Rho regulates T cell receptor ITAM-induced lymphocyte spreading in an integrin-independent manner

T cell receptor (TCR) engagement increases integrin-mediated adhesion to APC, resulting in the stabilization of the T cell : APC interaction and the close apposition of the two cell membranes. Here we show that engagement of either the TCR or CD3 chimeras with immobilized antibodies causes the rapid spreading of T cells in an integrin-independent fashion. This effect concurs with the polymerization of the actin cytoskeleton and is dependent on the integrity of the immunoreceptor tyrosine-based activation motifs of the CD3 subunits. Expression of a dominant negative mutant of RhoA, as well as the Rho-specific inhibitor C3 toxin, abolished TCR-induced spreading. In contrast, constitutively active or dominant negative forms of Rac and Cdc42 did not affect cell spreading. We conclude that signals emanating from the TCR can directly induce T cell spreading, independently of integrins, and via a Rho-dependent reorganization of the actin cytoskeleton.