Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor cells respond to hypoxic stress by upregulating a variety of genes involved in glucose uptake, glycolysis, and angiogenesis, all essential to maintaining nutrient availability and intracellular ATP levels. Adenosine monophosphate-dependent kinase (AMPK) is a key sensor for cellular homeostasis and is highly sensitive to changes in AMP:ATP ratios. The two catalytic AMPK alpha isoforms (AMPKalpha1, AMPKalpha2) were investigated with respect to their expression, cellular distribution, and contribution to VEGF expression under hypoxic stress in human U373 glioblastoma cells. Quantitative real-time PCR analysis showed AMPKalpha1 mRNA to be constitutively expressed in normoxia and hypoxia, whereas AMPKalpha2 mRNA levels were low in normoxia and significantly induced in hypoxia. Fluorescent immunohistochemistry showed that AMPKalpha2 protein redistributed to the nucleus under hypoxia, whereas AMPKalpha1 remained distributed throughout the cell. The AMPK chemical inhibitor, 5-iodotubericidin, effectively repressed the hypoxic induction of VEGF mRNA levels and hypoxia inducible factor-1 dependent transcription. AMPKalpha2 repression with RNA interference reduced hypoxia-induced VEGF mRNA and HIF-1 transcription, whereas AMPKalpha1 repression did not. Human glioblastoma cell lines U118 and U138 also showed hypoxia-induction of AMPKalpha2 as well as VEGF. Immunohistochemistry analysis of human astrocytoma/glioma samples revealed AMPKalpha2 present in high grade gliomas within hypoxic pseudopalisading microenvironments. These data suggest that prolonged hypoxia promotes the expression and functional activation of AMPKalpha2 and VEGF production in glioma cell lines and glioblastoma multiform tumors, thus contributing to tumor survival and angiogenesis in high grade human gliomas.
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PMID:AMP-dependent protein kinase alpha 2 isoform promotes hypoxia-induced VEGF expression in human glioblastoma. 1651 31

Malignant gliomas are typically angiogenic and secrete high levels of VEGF. Hypoxia has been identified as an important regulator of VEGF. However, malignant gliomas express high levels of VEGF in both hypoxic perinecrotic and vital tumor areas. In this study, we examined intracellular signaling pathways involved in the secretion of VEGF in glioma cells under normoxic conditions. Human malignant glioma cell lines, T98G, U373MG, U87MG, and A172, and human fetal lung fibroblasts (HFL) were cultured both with and without IL-1beta under normoxic conditions. VEGF, IL-1, IL-6, and TNF-alpha were measured with ELISA. VEGF mRNA levels were estimated by RT-PCR. Inhibitors of COX-2, MAPK, and phosphatidyl inositol 3-kinase (PI3-K), and blocking antibodies to TGF-beta II and TNF-alpha, or IL-1 receptor antagonist, were used to examine their effects on VEGF secretion. Phosphorylation of MAPK was examined by immunoblotting. The basal levels of VEGF secretion were significantly higher in U87MG, U373MG, and T98G, than HFL. IL-1beta significantly stimulated VEGF secretion in these glioma cells. Inhibitors of p38 MAPK and/or JNK significantly suppressed VEGF secretion both in the presence and absence of IL-1beta, while inhibitors of COX-2, ERK1/2, and PI3-K did not. Constitutive phosphorylation of p38 MAPK and JNK was observed in these glioma cells. The levels of IL-1beta in U87MG were significantly higher than in other glioma cell lines, and IL-1 receptor antagonist suppressed basal secretion of VEGF from U87MG. In conclusion, p38 MAPK and JNK pathways play an important role in VEGF secretion from malignant glioma cells under normoxic conditions, possibly contributing to VEGF-induced angiogenesis in malignant gliomas at vital tumor areas where there is no hypoxia.
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PMID:Activation of p38 MAPK and/or JNK contributes to increased levels of VEGF secretion in human malignant glioma cells. 1696 94

Nordy is a synthesized chrial compound. To investigate the effects of nordy (25 - 100 micromol x L(-1)) on the function of formylpeptide receptor (FPR) of malignant human glioma cells, human glioblastoma cell line U87 was used to detect its proliferation, migration, calcium mobilization, vascular endothelial growth factor (VEGF) mRNA and protein levels after activation of FPR by its agonist N-formyl-methionyl-leucyl-phenylalanine (fMLF). Cell proliferation, migration ability, VEGF mRNA, VEGF protein and calcium mobilization were evaluated by cell counting, chemotaxis assay, RT-PCR, ELISA and spectrometry. Nordy (50 - 100 micromol x L(-1)) potently inhibited the proliferation, migration and calcium mobilization of U87 cells induced by fMLF (P < 0.05). Moreover, 100 micromol x L(-1) nordy showed a significantly impaired VEGF mRNA expression and protein secretion induced by fMLF (P < 0.05). Nordy could inhibit FPR functioning in glioma cell proliferation, migration and angiogenesis, which might be a possible mechanism of its anti-cancer effects.
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PMID:[Effect of nordy on FPR function of malignant human glioma cell line U87]. 1752 Aug 23

Glial cells are generally considered to contribute to retaining the integrity of neural function through the protection of neuronal cells against neurodegenerative insults and also expected to play a potential role in the protection of cerebrovascular systems from various toxic insults of hemorrhaged blood, thus proposing a possible implication of glial cells in the recovery of brain function from the damage caused by cerebral hemorrhage. Based on this hypothetical idea, the direct effect of hemin on the expression of genes encoding heme oxygenase-1 (HO-1), vascular endothelial growth factor (VEGF), and brain-derived neurotrophic factor (BDNF) in glial cells was examined using rat C6 glioma cells as an in vitro model system. Hemin elevated both HO-1 and VEGF mRNA levels in the glioma cells at the concentration causing no critical damage to the cells, and the elevation of BDNF mRNA levels was also observed by exposing the cells to hemin under the same conditions. Furthermore, the elevation of VEGF and BDNF mRNA levels induced by hemin was blocked by pretreatment of the cells with the agents inhibiting not only HO-1 gene expression but also its enzymatic activity. These pharmacological studies indicate that hemin can induce the enhancement of VEGF and BDNF gene expression probably through the mechanism mediated by HO-1 activity in the glioma cells, proposing the possibility that glial cells are capable of contributing to the recovery of brain function from the damage caused by cerebral hemorrhage through the production of neurogenic and angiogenic factors.
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PMID:Possible relation of hemin-induced HO-1 expression to the upregulation of VEGF and BDNF mRNA levels in rat C6 glioma cells. 1893 73

Transcriptional targeting of viral genes is a promising strategy to achieve tumor-specific replication of oncolytic viruses. Due to its natural tropism, herpes simplex virus type 1 (HSV-1) may be an ideal tool for oncolytic therapy of brain tumors such as malignant glioblastoma. To study whether glioma-specific gene expression can be accomplished within the HSV-1 genome, four cellular regulatory elements were exemplarily studied. Whereas the human telomerase reverse transcriptase (hTERT) and survivin promoters and the nestin and vascular endothelial growth factor A (VEGF-A) enhancers displayed pronounced glioma specificity after plasmid transfection, only the nestin enhancer conferred a certain selectivity for glioma cells and notable activity when transferred into the viral genome. The nestin enhancer was also found to be highly useful for tumor cell-specific expression of a therapeutically relevant gene (interleukin-2) when tested in combination with the hTERT or simian virus 40 (SV40) early promoter in the HSV-1 genome. Because activity of the chosen promoter in a tumor is a prerequisite for the successful application of an oncolytic virus, we examined whether the activity of a promoter can be deduced from the amounts of cellular mRNA or protein expressed under its control. We found little correlation between promoter activity and mRNA levels of the corresponding gene, whereas protein expression was more closely related to promoter activity. We conclude that the cellular elements are differently regulated in the viral and cellular genomes. Mechanistic insight into the differential regulation is required to improve and refine the design of transcriptionally targeted HSV vectors.
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PMID:Tumor-specific activity of cellular regulatory elements is down-regulated upon insertion into the herpes simplex virus genome. 1897 78

Canonical Transient Receptor Potential (TRPC) channels play important roles in diverse physiological processes. The contribution of TRPC channels to up-regulate VEGF expression under hypoxic conditions was studied in a malignant glioma cell line, U-87 MG cells. Up-regulation of VEGF gene expression by hypoxia was markedly suppressed by a TRPC channel blocker. RT-PCR showed that U-87 MG cells expressed four TRPC isoforms in normoxia: TRPC1, 3, 4, and 5. In addition, the expression of TRPC3, 4, and 5 decreased greatly under hypoxia exposure in U-87 MG cells. In contrast, TRPC1 expression was unchanged. These results suggest TRPC channels were involved in hypoxia-induced VEGF expression, and compared with other TRPC isoforms, TRPC1 might play a different role in this process. Furthermore, we determined the function of TRPC1 by RNAi. Two different siRNAs against TRPC1 largely inhibited hypoxia-induced up-regulation of VEGF mRNA and protein levels. However, overexpression of TRPC3 or 5 neither enhanced hypoxia-induced VEGF expression, nor prevented it. Taken together, our present data suggest that TRPC1, but not TRPC3 or 5, is involved in hypoxia-induced VEGF expression in U-87 MG cells.
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PMID:Hypoxia up-regulates vascular endothelial growth factor in U-87 MG cells: involvement of TRPC1. 1944 5

We reported that PAX6 suppresses glioblastoma cell growth in vivo and anchorage-independent growth without significant alteration of cell proliferation in vitro, suggesting that PAX6 may alter the tumor microenvironment. Because we found that PAX6 downregulates expression of the gene encoding vascular endothelial growth factor A (VEGFA) in glioma cells, we used a subcutaneous xenograft model to verify PAX6 suppression of VEGFA-induced angiogenesis based on CD31-immunostaining of endothelial cells. The results showed a significant reduction of VEGFA at the transcription level in PAX6-transfected cells in xenografts and PAX6 has a suppressive effect on the microvascular amplification typically seen in glioblastoma. We showed that PAX6 suppression of VEGFA expression requires its DNA binding-domain. The C-terminal truncation mutant of PAX6, however, did not show the dominant negative function in regulating VEGFA expression that it showed previously in regulating MMP2 expression. In the glioma cell line U251HF, we further determined that blocking the PI3K/Akt signaling pathway with either adenoviral-mediated PTEN expression or LY294002 enhanced PAX6-mediated suppression of VEGFA in an additive manner; thus, PAX6-mediated suppression of VEGFA is not via the canonical pathway through HIF1A. These two VEGFA-regulatory pathways can also be similarly modulated in another malignant glioma cell line, U87, but not in LN229 where the basal VEGFA level is low and PTEN is wild-type. PAX6 suppression of VEGFA appears to be blocked in LN229. In conclusion, our data showed that PAX6 can initiate in glioma cells a new signaling pathway independent of PI3K/Akt-HIF1A signaling to suppress VEGFA expression.
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PMID:PAX6 suppression of glioma angiogenesis and the expression of vascular endothelial growth factor A. 1961 19

Down-regulation of vascular endothelial growth factor (VEGF) in the mouse leads to progressive and selective degeneration of motor neurons similar to amyotrophic lateral sclerosis (ALS). In mice expressing ALS-associated mutant superoxide dismutase 1 (SOD1), VEGF mRNA expression in the spinal cord declines significantly prior to the onset of clinical manifestations. In vitro models suggest that dysregulation of VEGF mRNA stability contributes to that decline. Here, we show that the major RNA stabilizer, Hu Antigen R (HuR), and TIA-1-related protein (TIAR) colocalize with mutant SOD1 in mouse spinal cord extracts and cultured glioma cells. The colocalization was markedly reduced or abolished by RNase treatment. Immunoanalysis of transfected cells indicated that colocalization occurred in insoluble aggregates and inclusions. RNA immunoprecipitation showed a significant loss of VEGF mRNA binding to HuR and TIAR in mutant SOD1 cells, and there was marked depletion of HuR from polysomes. Ectopic expression of HuR in mutant SOD1 cells more than doubled the mRNA half-life of VEGF and significantly increased expression to that of wild-type SOD1 control. Cellular effects produced by mutant SOD1, including impaired mitochondrial function and oxidative stress-induced apoptosis, were reversed by HuR in a gene dose-dependent pattern. In summary, our findings indicate that mutant SOD1 impairs post-transcriptional regulation by sequestering key regulatory RNA-binding proteins. The rescue effect of HuR suggests that this impairment, whether related to VEGF or other potential mRNA targets, contributes to cytotoxicity in ALS.
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PMID:Amyotrophic lateral sclerosis-linked mutant SOD1 sequesters Hu antigen R (HuR) and TIA-1-related protein (TIAR): implications for impaired post-transcriptional regulation of vascular endothelial growth factor. 1980 46

The proliferative and antiapoptotic actions of endothelin (ET)-1 in cancer cells have been documented and ET receptor antagonists have been exploited as potential anticancer drugs. Glioblastoma cell lines express both ETA and ETB receptors and previous works have shown that ETB receptors are involved in the proliferation of different cancer cell types. In this study we have investigated the effects of two structurally unrelated ETB receptor antagonists, BQ788 and A192621, on cell survival, proliferation and apoptosis in 1321-N1, U87 and IPDDCA2 glioma cell lines. BQ788 and A192621 reduced glioma cells viability and proliferation assessed by BrdU incorporation and cell cycle analysis by flow cytometry, while in contrast the ETA receptor antagonist BQ123 had no effect on cell survival. TUNEL assay and immunocytochemical experiments showed that BQ788 and A192621 trigger apoptotic processes mainly via activation of the intrinsic mitochondrial pathway involving caspase-9 activation, AIF release and cytochrome c translocation. Furthermore, treatment with ETB antagonists downregulates ERK- and p38MAPK-dependent pathways but does not affect VEGF mRNA levels. Our findings support the hypothesis that ETB antagonists represent a new promising therapeutic strategy for the treatment of high grade gliomas.
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PMID:Endothelin B receptor antagonists block proliferation and induce apoptosis in glioma cells. 1993 93

Recent evidence suggests that vascular permeability and the presence of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) are important mediators of brain tumor growth in addition to angiogenesis. Perfusion and permeability magnetic resonance (MR) imaging can now measure parameters such as cerebral blood volume and vascular permeability, which can be directly correlated with these histopathologic changes as well as molecular markers such as VEGF. The major techniques currently used in both the clinical and research settings are T1-weighted steady-state dynamic contrast-enhanced MR imaging (DCE MR imaging) and T2 *-weighted first-pass, dynamic susceptibility contrast MR imaging (DSC MR imaging). The advantages and disadvantages of each technique with regard to characterizing tumor biology are discussed in this article. Most clinicians and investigators are currently using the DSC MR imaging T2 *-weighted technique for brain tumor perfusion MR imaging. The existence of multiple approaches to pathologic classification of human glioma implies that there is a lack of consensus among experts as to which is the single best approach. These multiple grading systems do, however, agree on the histologic parameters that are important in the determination of glioma biology, namely hypercellularity, pleomorphism, vascular endothelial proliferation, mitotic activity, and necrosis.
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PMID:Magnetic resonance perfusion and permeability imaging in brain tumors. 1995 4


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