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)

We have previously suggested that tumor angiogenesis in human gliomas is regulated by a paracrine mechanism involving vascular endothelial growth factor (VEGF) and flt-1 (VEGF-receptor 1). VEGF, an endothelial-cell-specific mitogen, is abundantly expressed in glioma cells which reside along necrotic areas, whereas flt-1, a tyrosine-kinase receptor for VEGF, is expressed in tumor endothelial cells, but not in endothelial cells in normal adult brain. Recently, a second tyrosine-kinase receptor which binds VEGF with high affinity, designated KDR or flk-1, has been described. We performed in situ hybridization for VEGF mRNA, flt-1 mRNA and KDR mRNA on serial sections of normal brain, low-grade and high-grade glioma specimens. We show that KDR mRNA is co-expressed with flt-1 in vascular cells in glioblastoma but not in low-grade glioma. Since flt-1 and KDR are not expressed in endothelial cells in the normal adult brain, the coordinate up-regulation of 2 receptors for VEGF appears to be a critical event which controls tumor angiogenesis. Immunocytochemistry with a monoclonal anti-VEGF antibody revealed significant amounts of VEGF protein in the same glioma cells that expressed VEGF mRNA. The largest amount of VEGF immunoreactivity, however, was detected on the vasculature of glioblastomas, the site where VEGF exerts its biological functions. These findings suggest that VEGF is produced and secreted by glioma cells and acts on tumor endothelial cells which express VEGF receptors. To further characterize VEGF-producer cells in vivo, we investigated cellular proliferation, immunoreactivity to the p53 tumor-suppressor gene product and epidermal-growth-factor-receptor (EGFR) expression on serial sections by immunocytochemistry. VEGF-producer cells did not show increased cellular proliferation, p53 immunoreactivity or EGFR immunoreactivity as compared with glioma cells which did not express VEGF. Our studies therefore do not demonstrate evidence for a growth advantage of VEGF-producer cells in vivo or VEGF induction by p53 mutation or EGFR over-expression.
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PMID:Vascular endothelial growth factor and glioma angiogenesis: coordinate induction of VEGF receptors, distribution of VEGF protein and possible in vivo regulatory mechanisms. 752 92

Capillary hemangioblastoma is the most frequent manifestation of the autosomal dominantly inherited von Hippel-Lindau (VHL) disease but also presents as a nonfamilial, sporadic vascular tumor. Hemangioblastomas are characterized by a dense network of capillaries in association with cysts. To investigate the mechanisms underlying neovascularization and cyst formation, we analyzed eight VHL disease-associated and five sporadic hemangioblastomas. Histologically, both tumor types showed a similar phenotype. The capillaries expressed the endothelial cell markers von Willebrand factor and CD31 antigen. We investigated the expression of vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen which is also known to induce vascular permeability in vivo, and its high affinity tyrosine kinase receptors flt-1 and KDR. Northern blot and in situ hybridization analysis revealed significant up-regulation of VEGF and VEGF receptor expression in VHL disease-associated and sporadic hemangioblastomas compared to normal brain and tumor stromal cells as sites of abundant VEGF transcription. Endothelial cells did not express detectable amounts of VEGF mRNA but coexpressed flt-1 and KDR. By immunohistochemistry, VEGF protein was detectable in the tumor interstitium and was found to be concentrated around capillaries. Performing reverse transcription-PCR, we demonstrated that VEGF121 and VEGF165 were the splice variants predominantly expressed, whereas mRNA encoding VEGF189 was present at smaller amounts. Our findings suggest that, in VHL disease-associated and sporadic hemangioblastomas, VEGF121 and VEGF165 are secreted by stromal cells and interact with the corresponding VEGF receptors expressed on tumor endothelial cells. This paracrine mechanism may mediate neovascularization and cyst formation in capillary hemangioblastomas.
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PMID:Up-regulation of vascular endothelial growth factor and its receptors in von Hippel-Lindau disease-associated and sporadic hemangioblastomas. 753 61

To investigate the relationship between angiogenesis and hepatic tumorigenesis, we examined the expression of vascular endothelial growth factor (VEGF) in 8 human colon carcinoma cell lines and in 30 human colorectal cancer liver metastases. Abundant message for VEGF was found in all tumors, localized to the malignant cells within each neoplasm. Two receptors for VEGF, KDR and flt1, were also demonstrated in most of the tumors examined. KDR and flt1 mRNA were limited to tumor endothelial cells and were more strongly expressed in the hepatic metastases than in the sinusoidal endothelium of the surrounding liver parenchyma. VEGF monoclonal antibody administration in tumor-bearing athymic mice led to a dose- and time-dependent inhibition of growth of subcutaneous xenografts and to a marked reduction in the number and size of experimental liver metastases. In hepatic metastases of VEGF antibody-treated mice, neither blood vessels nor expression of the mouse KDR homologue flk-1 could be demonstrated. These data indicate that VEGF is a commonly expressed angiogenic factor in human colorectal cancer metastases, that VEGF receptors are up-regulated as a concomitant of hepatic tumorigenesis, and that modulation of VEGF gene expression or activity may represent a potentially effective antineoplastic therapy in colorectal cancer.
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PMID:Regulation by vascular endothelial growth factor of human colon cancer tumorigenesis in a mouse model of experimental liver metastasis. 753 99

Vasculotropin (VAS), also called vascular endothelial growth factor (VEGF) or vascular permeability factor, is a secreted growth factor whose target cell specificity has been reported as restricted to vascular endothelium. Its effects are mediated by at least two distinct membrane-spanning tyrosine kinase receptors, KDR and flt-1; the expression of which also seems restricted to vascular endothelium. We describe here that cultured human retinal pigment epithelial (HRPE) cells express both KDR and flt-1 receptors, bind VAS/VEGF on two high affinity sites (apparent Kd of 9 and 210 pM corresponding to 940 and 18,800 sites per cell) and proliferate or migrate upon recombinant VAS/VEGF addition. HRPE cells also express the mRNA corresponding to the 121 and 165 amino acid forms of VAS/VEGF. HRPE cells release in their own culture medium and store in their extracellular matrix self-mitogenic and chemoattractant factors indistinguishable from 121 and 165 VAS/VEGF isoforms. The autocrine role of VAS/VEGF was confirmed by the inhibition of these bioactivities by neutralizing specific anti-VAS/VEGF antibodies.
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PMID:Vasculotropin/vascular endothelial growth factor is an autocrine growth factor for human retinal pigment epithelial cells cultured in vitro. 762 84

To elucidate the pathogenesis of thyroid gland hypervascularity in patients with Graves' disease, we studied the expression of mRNAs for vascular endothelial growth factor (VEGF) and its receptor, Flt family, using human thyroid follicles in vitro and thiouracil-fed rats in vivo. Human thyroid follicles, cultured in the absence of endothelial cells, secreted de novo-synthesized thyroid hormone in response to thyroid-stimulating hormone (TSH) and Graves' IgG. The thyroid follicles produced VEGF mRNA but not flt-1 mRNA. The expression of VEGF mRNA was enhanced by insulin, tumor-promoting phorbol ester, calcium ionophore, dibutyryl cAMP, TSH, and Graves' IgG. When rats were fed thiouracil for 4 wk, their serum levels of TSH were increased at day 3. VEGF mRNA was also increased on day 3, accompanied by an increase in flt family (flt-1 and KDR/ flk-1) mRNA expression. These in vitro and in vivo findings suggest that VEGF is produced by thyroid follicles in response to stimulators of TSH receptors, via the protein kinase A and C pathways. VEGF, a secretable angiogenesis factor, subsequently stimulates Flt receptors on endothelial cells in a paracrine manner, leading to their proliferation and producing hypervascularity of the thyroid gland, as seen in patients with Graves' disease.
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PMID:Stimulation by thyroid-stimulating hormone and Grave's immunoglobulin G of vascular endothelial growth factor mRNA expression in human thyroid follicles in vitro and flt mRNA expression in the rat thyroid in vivo. 765 4

We studied the correlation between expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and their receptors with vascularity, metastasis, and proliferative index of human colon cancers. Immunohistochemical analyses using antibodies against VEGF, bFGF, their receptors (KDR, flt-1, bek, and flg), factor VIII, and proliferating cell nuclear antigen were carried out on archival specimens of 52 human colon carcinomas and 10 adenomas. Vessels were quantitated by light microscopy (x200), and the intensity of staining for VEGF and bFGF was assessed on a scale of 0-3+. The presence or absence of immunostaining for KDR, flt-1, bek, and flg was evaluated in endothelial cells, and proliferation was determined by counting the number of proliferating cell nuclear antigen-positive cells per 500 tumor cells. Expression of VEGF and KDR was higher in metastatic than in nonmetastatic neoplasms and directly correlated with the extent of neovascularization and the degree of proliferation, whereas expression of bFGF, flt-1, bek, and flg did not differ among tumor types. Vessel counts were greater in metastatic tumors than in nonmetastatic tumors. These findings support the hypothesis that VEGF is an important angiogenic factor in primary and metastatic human colon cancer. VEGF expression and vessel counts may aid in predicting patients at risk for metastasis from colon cancer.
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PMID:Expression of vascular endothelial growth factor and its receptor, KDR, correlates with vascularity, metastasis, and proliferation of human colon cancer. 766 63

FLT4 is a recently cloned gene encoding a transmembrane tyrosine kinase related to the FLT1 and KDR/FLK1 vascular endothelial growth factor receptors. We have previously shown that FLT4 is expressed as transcripts of 4.5 and 5.8 kb in several human fetal and adult tissues. Here we show that these transcripts encode two polypeptides, FLT4s (short) and FLT41 (long), which are proteolytically processed in transfected cells and leukemia cells and which have different carboxy terminal tails. The 3' coding region of the 5.8 kb mRNA was found to be 65 codons longer than that of the the 4.5 kb mRNA. Analysis of the genomic structure of the region encoding the two carboxy termini revealed that the two transcripts are generated by alternative polyadenylation and subsequent alternative splicing during RNA processing. Our findings thus show regulation of FLT4 structure in the carboxy terminal tail considered important for receptor function. The significance of the two forms may relate to the role of additional potential autophosphorylation sites in the FLT4 long form.
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PMID:Two human FLT4 receptor tyrosine kinase isoforms with distinct carboxy terminal tails are produced by alternative processing of primary transcripts. 769 69

Endothelial cells constitute an essential integrator of factors that effect blood vessel remodeling induced by chronic hypoxia. We hypothesized that vascular endothelial growth factor (VEGF) may participate in the lung response to acute and to chronic hypoxia. We found that ex vivo perfusion of isolated lungs under hypoxic conditions (when compared with normoxia) caused an increase in lung tissue mRNA of VEGF and of the VEGF receptors KDR/Flk and Flt. Chronic hypobaric hypoxia also increased lung tissue mRNA levels of VEGF, KDR/Flk, and Flt and the amount of VEGF protein. In situ hybridization studies demonstrated increased VEGF and KDR/flk hybridization signals in lungs from chronically hypoxic rats. Since endotoxin treatment of rats decreased lung VEGF mRNA, we postulated that nitric oxide (NO) or an NO-related metabolite might be involved in lung VEGF gene expression. Indeed, sodium nitroprusside, a NO donor, decreased and L-NAME (N-nitro-L-arginine methyl ester), an inhibitor of NO-synthesis, increased both VEGF and VEGF receptor transcripts. We conclude that VEGF in the isolated perfused lung acts as an early gene in response to hypoxia and that lung VEGF and VEGF receptor mRNA levels are influenced by hypoxia and NO-dependent mechanisms.
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PMID:Increased gene expression for VEGF and the VEGF receptors KDR/Flk and Flt in lungs exposed to acute or to chronic hypoxia. Modulation of gene expression by nitric oxide. 770 86

We have recently cloned the human fms-like tyrosine kinase 4 gene FLT4, whose protein product is related to two vascular endothelial growth factor receptors FLT1 and KDR/FLK1. Here the expression of FLT4 has been analyzed by in situ hybridization during mouse embryogenesis and in adult human tissues. The FLT4 mRNA signals first became detectable in the angioblasts of head mesenchyme, the cardinal vein, and extraembryonally in the allantois of 8.5-day postcoitus (p.c.) embryos. In 12.5-day p.c. embryos, the FLT4 signal decorated developing venous and presumptive lymphatic endothelia, but arterial endothelia were negative. During later stages of development, FLT4 mRNA became restricted to vascular plexuses devoid of red cells, representing developing lymphatic vessels. Only the lymphatic endothelia and some high endothelial venules expressed FLT4 mRNA in adult human tissues. Increased expression occurred in lymphatic sinuses in metastatic lymph nodes and in lymphangioma. Our results suggest that FLT4 is a marker for lymphatic vessels and some high endothelial venules in human adult tissues. They also support the theory on the venous origin of lymphatic vessels.
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PMID:Expression of the fms-like tyrosine kinase 4 gene becomes restricted to lymphatic endothelium during development. 772 99

Vascular permeability factor (VPF), also known as vascular endothelial growth factor (VEGF), plays an important role in the increased vascular permeability and angiogenesis associated with many malignant tumors. In addition, VPF/VEGF is strongly expressed by epidermal keratinocytes in wound healing and psoriasis, disorders that are also characterized by increased microvascular permeability and angiogenesis. In this study, we investigated the expression of VPF/VEGF in three bullous diseases with subepidermal blister formation that are characterized by hyperpermeable dermal microvessels and pronounced papillary dermal edema. The expression of VPF/VEGF mRNA was strongly up-regulated in the lesional epidermis of bullous pemphigoid (n = 3), erythema multiforme (n = 3), and dermatitis herpetiformis (n = 4) as detected by in situ hybridization. Epidermal labeling was particularly intense over blisters, but strong expression was also noted in areas of the epidermis adjacent to dermal inflammatory infiltrates at a distance from blisters. Moreover, the VPF/VEGF receptors, flt-1 and KDR, were up-regulated in endothelial cells in superficial dermal microvessels. High levels of VPF/VEGF (138-238 pM) were detected in blister fluids obtained from five patients with bullous pemphigoid. Addition of blister fluid to human dermal microvascular endothelial cells exerted a dose-dependent mitogenic effect that was suppressed after depletion of VPF/VEGF by immunoadsorption. These findings strongly suggest that VPF/VEGF plays an important role in the induction of increased microvascular permeability in bullous diseases, leading to papillary edema and fibrin deposition and contributing to the bulla formation characteristic of these disorders.
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PMID:Increased expression of vascular permeability factor (vascular endothelial growth factor) in bullous pemphigoid, dermatitis herpetiformis, and erythema multiforme. 773 51


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