Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vascular endothelial growth factor (VEGF) is an important factor for endothelial cell proliferation and a key regulator of blood vessel development in embryos and angiogenesis in adult tissues. Its biological activity is mediated by two receptor tyrosine kinases, VEGFR-1 (Flt-1) and VEGFR-2 (KDR). In contrast to VEGFR-2, a naturally occurring soluble form of the VEGFR-1 (sVEGFR-1) is produced by endothelial cells by differential splicing of the flt-1 gene, and it is a secreted gene product. In order to develop a specific enzyme-linked immunosorbent assay (ELISA) for the measurement of sVEGFR-1, we established five anti-human receptor antibodies and characterized them in detail. These antibodies recognize different epitopes located within the seven Ig-like domains of the extracellular receptor protein but have no neutralizing activity in ligand binding assays. Together with a polyclonal antiserum, a specific human sVEGFR-1 ELISA was developed using the mAb #190.11. The ELISA can detect human sVEGFR-1 with a minimum detection limit of 1 ng/ml. The ELISA does not show any cross-reactivity with other related soluble receptors. Using this assay, human sVEGFR-1 was measured in the supernatant of different VEGFR-1 expressing cell types. No sVEGFR-1 protein was detectable after heparin Sepharose treatment or size-exclusion filtration (< 30 kDa). The ELISA assay for sVEGFR-1 was also used to measure the amount of the soluble receptor in amniotic fluid samples of patients undergoing amniocentesis during the course of normal pregnancies. The concentration of the samples was in the range of 5-35 ng/ml. This ELISA could be useful powerful tool for investigations concerning the physiological function of the soluble receptor under normal and pathophysiological conditions.Furthermore, it may facilitate studies of the mechanisms of receptor production.
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PMID:Detection and quantification of complexed and free soluble human vascular endothelial growth factor receptor-1 (sVEGFR-1) by ELISA. 1041 Sep 82

The retinal pigment epithelium (RPE) maintains the choriocapillaris (CC) in the normal eye and is involved in the pathogenesis of choroidal neovascularization in age-related macular degeneration. Vascular endothelial growth factor-A (VEGF) is produced by differentiated human RPE cells in vitro and in vivo and may be involved in paracrine signaling between the RPE and the CC. We investigated whether there is a polarized secretion of VEGF by RPE cells in vitro. Also, the localization of VEGF receptors in the human retina was investigated. We observed that highly differentiated human RPE cells, cultured on transwell filters in normoxic conditions, produced two- to sevenfold more VEGF toward their basolateral side as compared to the apical side. In hypoxic conditions, VEGF-A secretion increased to the basal side only, resulting in a three- to 10-fold higher basolateral secretion. By immunohistochemistry in 30 human eyes and in two cynomolgus monkey eyes, KDR (VEGFR-2) and flt-4 (VEGFR-3) were preferentially localized at the side of the CC endothelium facing the RPE cell layer, whereas flt-1 (VEGFR-1) was found on the inner CC and on other choroidal vessels. Our results indicate that RPE secretes VEGF toward its basal side where its receptor KDR is located on the adjacent CC endothelium, suggesting a role of VEGF in a paracrine relation, possibly in cooperation with flt-4 and its ligand. This can explain the known trophic function of the RPE in the maintenance of the CC and its fenestrated permeable phenotype and points to a role for VEGF in normal eye functioning. Up-regulated basolateral VEGF secretion by RPE in hypoxia or loss of polarity of VEGF production may play a role in the pathogenesis of choroidal neovascularization.
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PMID:Polarized vascular endothelial growth factor secretion by human retinal pigment epithelium and localization of vascular endothelial growth factor receptors on the inner choriocapillaris. Evidence for a trophic paracrine relation. 1043 35

Many of the cellular actions of thrombin may contribute to the angiogenesis-promoting effect of thrombin reported previously. In this study, we investigated the interaction between thrombin and vascular endothelial growth factor (VEGF), the specific endothelial cell mitogen and key angiogenic factor. Exposure of human umbilical vein endothelial cells to thrombin sensitizes these cells to the mitogenic activity of VEGF. This thrombin-mediated effect is specific, dose-dependent and requires the activated thrombin receptor. Quantitative reverse transcription- polymerase chain reaction analysis reveals a time- and dose-dependent up-regulation of mRNA for VEGF receptors (KDR and flt-1). Optimal thrombin concentration for maximal expression of mRNA for KDR is 1.5 IU/ml (170% over controls) and appears 8-12 h after thrombin stimulation. Nuclear run-on experiments demonstrate that the up-regulation of KDR mRNA by thrombin occurred at the transcriptional level. In addition, functional protein of KDR receptor is increased to about 200% over control after 12 h of thrombin treatment. The up-regulation of KDR and flt-1 mRNA is also mimicked by the thrombin receptor activating peptide. These findings could explain at least in part the potent angiogenic action of thrombin.
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PMID:On the mechanism of thrombin-induced angiogenesis. Potentiation of vascular endothelial growth factor activity on endothelial cells by up-regulation of its receptors. 1044 65

Angiogenesis is a complex process that includes recruitment and proliferation of mural cells-smooth muscle cells (SMC) and pericytes. Vascular endothelial growth factor (VEGF) has been shown to play an important role in angiogenesis and is an endothelial cell chemoattractant. In addition, certain VEGF isoforms have been implicated in the normal formation of smooth muscle cell-surrounded arteries. Because VEGF's role as a mural cell chemoattractant had not been explored, we examined the ability of VEGF to influence vascular SMC migration in vitro. A Boyden chamber migration assay demonstrated that VEGF (0-100 ng/ml) caused a dose-dependent migration of SMC. VEGF did not cause proliferation of SMC. Reverse transcriptase-polymerase chain reaction analysis demonstrated the presence of both KDR and flt mRNA, two known VEGF receptors, in SMC cultures. Western blot analysis of SMC lysates confirmed these data, revealing bands migrating at approximately 200 kDa and slightly below 200 kDa consistent with KDR and flt. These observations demonstrate that VEGF receptors are present on SMC, and that VEGF can act as an SMC chemoattractant.
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PMID:Vascular endothelial growth factor-induced migration of vascular smooth muscle cells in vitro. 1045 28

There is accumulating evidence that deficient trophoblast invasion of the placental bed spiral arteries is crucial to the pathogenesis of pre-eclampsia and intrauterine growth restriction. However, the factors which regulate the process of trophoblast invasion remain unclear. We have investigated whether extravillous trophoblast invasion and motility are mediated by the angiogenic growth factors, vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). The SGHPL-4 extravillous trophoblast cell line was utilized. Expression of mRNA for the receptors of VEGF and PlGF (KDR and flt-1) was determined using the reverse transcriptase polymerase chain reaction. An in vitro model of invasion assessed the number and length of trophoblast processes invading into an extracellular matrix. The motility of cells under standard culture conditions was also quantified. The effect of the addition of VEGF and PlGF (+/-heparin) on trophoblast invasion and motility was determined. The effect of VEGF and PlGF (+/-heparin) on SGHPL-4 cell proliferation was assessed by cell counts at 24, 48 and 72 h post-addition of growth factor. The SGHPL-4 cells expressed mRNA for the flt-1 but not the KDR receptor. The addition of VEGF resulted in a significant decrease in the number of trophoblast processes formed (P< 0.02); this effect was not influenced by the addition of heparin. However, there was no effect on the length of processes formed in response to VEGF (+/-heparin). The addition of PlGF had no effect on either the number or the length of processes formed. The addition of VEGF increased the motility of the SGHPL-4 cells (P< 0.002); the addition of heparin prevented this VEGF-induced increase in motility. The addition of PlGF had no effect on SGHPL-4 motility (+/-heparin). Neither growth factor had any effect on the proliferative ability of SGHPL-4 cells. Contrary to our hypothesis, we did not find that the angiogenic growth factors, VEGF and PlGF, mediated the in vitro invasion of trophoblast cells into an extracellular matrix. However, VEGF did increase trophoblast motility. Our findings of an effect of VEGF on trophoblast motility (and possibly invasion) suggests the presence of functional receptors, which can mediate the actions of VEGF. Caution must be exercised before any extrapolation to the in vivo situation, however, it could be speculated that the increased motility in response to VEGF may be an initial response to attract trophoblast cells to the decidua, and that VEGF might then limit the degree to which trophoblast cells invade.
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PMID:The effects of angiogenic growth factors on extravillous trophoblast invasion and motility. 1094 Feb 13

Vascular endothelial growth factor (VEGF) is a major angiogenic factor. Osteosarcoma is characterised by hypervascularity and metastatic potential. We examined VEGF mRNA expression, VEGF isoform pattern and VEGF receptor (flt-1 and KDR) by RT-PCR analysis in 30 osteosarcomas. All 30 osteosarcomas expressed VEGF mRNA. 17 osteosarcomas (57%) expressed flt-1 mRNA, whilst 20 (67%) expressed KDR mRNA. 6/30 (20%) osteosarcomas were positive for VEGF121 only, 8 (27%) for VEGF121 + VEGF165, and 16 (53%) for VEGF121 + VEGF165 + VEGF189. Patients with osteosarcomas with VEGF165 (n = 24) had significantly poorer prognosis in comparison with those without VEGF165 (P = 0.022, Wilcoxon's test). The osteosarcomas with VEGF165 had significantly increased vascularity assessed on sections immunostained for CD34 (P < 0.001, Mann-Whitney U test). Although VEGF165 is a soluble isoform, it is also retained on the cellular surface. These results suggest that cell-retained VEGF isoforms (VEGF165, VEGF189) might be essential for neovascularisation in osteosarcoma, whilst the soluble VEGF121 isoform is not sufficient to stimulate neovascularisation in this type of neoplasm.
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PMID:Cell-retained isoforms of vascular endothelial growth factor (VEGF) are correlated with poor prognosis in osteosarcoma. 1053 53

Vascular endothelial growth factor (VEGF), which is one of the most potent angiogenic factors, has been shown to play a pivotal role in tumor angiogenesis, including hepatocellular carcinoma (HCC). The effects of VEGF are mediated mainly through two distinct receptors, flt-1 and KDR/Flk-1. It has been suggested that KDR/Flk-1 plays an important role in tumor development. However, the role of KDR/Flk-1 in HCC has not been examined. We previously reported that VEGF tightly regulated murine HCC development, based on the results of a study using a retroviral tetracycline-regulated (Retro-Tet) gene expression system. This system allows VEGF gene expression to be manipulated in vivo by providing tetracycline in the drinking water. In the present study, we combined the KDR/Flk-1-specific neutralizing monoclonal antibody (KDR/Flk-1mAb) and the Retro-Tet system to elucidate the role of KDR/Flk-1 in VEGF-induced tumor development and angiogenesis in a murine HCC experimental model. In a xenograft study, tumor augmentation induced by VEGF overexpression was almost abolished by means of KDR/Flk-1mAb treatment, with accompanying inhibition of angiogenesis, KDR/Flk-1 autophosphorylation, but not interference of flt-1 activation. This inhibitory effect was achieved even on established tumors and regardless of whether the tumor size was small or large. On the contrary, KDR/Flk-1mAb treatment significantly increased the apoptosis in the tumor. With orthotopic transplantation, KDR/Flk-1mAb also inhibited HCC development in the liver. These results suggest that KDR/Flk-1 is a major regulator of VEGF-mediated HCC development and angiogenesis not only at the initial stage, but also after the tumor has fully developed.
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PMID:KDR/Flk-1 is a major regulator of vascular endothelial growth factor-induced tumor development and angiogenesis in murine hepatocellular carcinoma cells. 1053 39

The expression patterns of vascular endothelial growth factor (VEGF) and its two receptors, flt-1 and KDR, were assessed in normal human melanocytes, transformed melanocytes expressing the simian virus 40 Tgene (SV40T), and melanoma cells derived from primary and metastatic lesions. Constitutive expression of VEGF, flt-1, and KDR mRNA and proteins was observed in the majority of primary and metastatic melanoma cell lines, and in SV40T-transformed melanocytes. VEGF expression in melanoma cell lines was further enhanced by exogenous growth factors including insulin and fetal calf serum. By contrast, neonatal melanocytes did not express VEGF or VEGF receptors and VEGF expression could not be induced by exogenous growth factors. Exogenous VEGF had no significant effects on melanoma cell proliferation or on production of a transcriptional target for VEGF, urokinase-type plasminogen activator. Down-regulation of VEGF expression in the metastatic melanoma cell line WM164 through transfection of a VEGF antisense construct similarly did not affect proliferation of the transfected cells in the presence or absence of exogenous VEGF. In summary, coexpression of VEGF and its receptors is a tumor-associated phenomenon in melanoma development. However VEGF production does not support autocrine proliferation of the melanoma cell lines tested.
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PMID:Melanoma-associated expression of vascular endothelial growth factor and its receptors FLT-1 and KDR. 1054 69

Angiogenesis, or development of blood vessels from preexisting vasculature, has important functions under both normal and pathophysiological conditions. Vascular endothelial growth factor receptors 1-3, also known as flt-1, KDR, and flt-4, are endothelial cell-specific receptor tyrosine kinases which serve as key mediators of the angiogenic responses. The review focuses on the signaling pathways that are initiated from these receptors and the recently identified VEGF coreceptor neuroplilin-1.
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PMID:Signaling via vascular endothelial growth factor receptors. 1057 17

Vascular endothelial growth factor (VEGF) is a potent angiogenic polypeptide that activates 2 distinct high-affinity tyrosine kinase receptors, flk-1/KDR and flt-1. In the present study, we characterized the expression of VEGF and its receptors flk-1/KDR and flt-1 in the normal human pancreas and in human pancreatic cancer tissues and cell lines. VEGF, flk-1/KDR and flt-1 mRNA levels were elevated in cancer tissues compared with normal pancreas. By immuno-histochemistry, VEGF, flk-1/KDR and flt-1 immunoreactivity co-localized in many of the cancer cells within the tumor mass. Three (AsPC-1, Capan-1 and MIAPaCa-2) of 6 pancreatic cancer cell lines expressed flk-1/KDR mRNA and protein, and 4 cell lines (AsPC-1, Capan-1, T3M4 and PANC-1) expressed flt-1 mRNA transcripts. Binding studies with (125)I-labeled VEGF165 indicated that only Capan-1 cells exhibited high levels of specific binding. Furthermore, VEGF enhanced the growth of Capan-1 cells but was without effect in the other cell lines. VEGF also enhanced mitogen-activated protein kinase (MAPK) phosphorylation and c-fos induction in Capan-1 cells, whereas the MAPK kinase inhibitor PD98059 abolished the growth-stimulatory effect of VEGF. These data indicate that human pancreatic cancers have the capacity to over-express VEGF and its receptors and suggest that in some instances VEGF may directly promote pancreatic cancer growth via the MAPK pathway.
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PMID:Concomitant over-expression of vascular endothelial growth factor and its receptors in pancreatic cancer. 1058 78


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