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)

The amino terminus of mouse epidermal growth factor (mEGF) was coupled directly to the aldehyde end of dextran through a reductive amination procedure. The highest coupling efficiency was approximately 80% and could be reached after approximately 24 h of reaction time at pH 8. Gel filtration on Sephadex G-50 Fine removed free mEGF from the conjugate. Preparative polyacrylamide gel electrophoresis was used to separate the conjugate from excess noncharged dextran. The conjugate bound specifically to the EGF receptor on cultured glioma cells as shown in displacement tests with free mEGF. The conjugate was stable in the pH interval 4-9, in 2 M sodium chloride, in 7 M urea, and in human serum and could still bind to the EGF receptor after such treatments. The conjugates are candidates for targeted nuclide therapy.
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PMID:Preparation and purification of an end to end coupled mEGF-dextran conjugate. 940 68

Cell-type specific transcription of the myelin basic protein (MBP) gene in primary oligodendrocytes (OL) is regulated by cis-acting regulatory elements located at both upstream and downstream of the TATA-box region of the MBP promoter. To identify cell-type specific factors that bind to the downstream regulatory elements, we utilised DNase I footprinting analysis and gel retardation assays with nuclear extracts from myelin-forming OL as well as a non-myelin forming cell line, C6 glioma (C6) cells. Several regions of DNA were protected from DNAse I digestion by nuclear extracts of both cell types. However, two regions, from -17 to +17 and from +47 to +58 were protected specifically in OL, while three regions, from + 17 to + 22, from +43 to +49 and from +58 to +64 were protected only with C6 nuclear extracts. Inspection of the protected regions for homology with known transcription factor binding sites revealed that sequences at from +47 to +58 and from +56 to +68 showed extensive homology to the negative regulatory element (NRE1), of the mouse renin gene and to the interferon (IFN) consensus sequence of major histocompatibility complex class I genes (MHC I-ICS), respectively. Gel retardation assays using a MHC I-ICS oligonucleotide and transient transfection assays using MBP-CAT constructs were used to study the effect of IFNs on MBP promoter activity in OL and C6 cells. In OL, IFN-alpha/beta caused little induction of CAT activity, but IFN-gamma resulted in a 2-3.5-fold decrease in CAT activity. In contrast, in C6 cells both IFN-alpha/beta and IFN-gamma induced a 1.5-2.5-fold increase in CAT activity. The cooperative effects of factors binding to NREs and ICS may be responsible for the cell-type specific regulation of MBP gene transcription.
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PMID:Cell-type specific factors bind to regulatory elements located downstream of the TATA-box element in the mouse myelin basic protein (MBP) gene promoter. 947 27

Progression of glioma is associated with local degenerative processes which are attributed to the activity of gelatinases. As glioma cells are candidate for secretion of these enzymes, we have studied in vitro the potential of cytokines (interleukin-1alpha (IL-1), tumor necrosis factor-alpha (TNFalpha) and transforming growth factor-beta (TGFbeta2)) to regulate the expression of gelatinase A and B (Gels A and B, respectively) in two glioma cells of human (A172) and rat origin (C6). We showed that IL-1 and TNFalpha both induced gene expression and protein secretion of Gel B in both cell lines, as revealed by RT-PCR and gelatin zymography, respectively. In C6 cells, TNFalpha had no effect on Gel A constitutive expression while IL-1 increased its production, but only at high doses. We have also demonstrated that TGFbeta2 inhibited both IL-1- or TNFalpha-induced gene expression and Gel B production in a dose-dependent manner but had no effect on Gel A secretion. The effect of TGFbeta2 on Gel B secretion was reversed by phorbol myristate acetate (PMA). Taken together, these data suggest that IL-1, TNFalpha and TGFbeta2 tightly regulate Gel B secretion in glioma cells, an enzyme which is believed to play an important role in the local invasion of brain tissue by tumor cells.
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PMID:In vitro expression of MMP-2 and MMP-9 in glioma cells following exposure to inflammatory mediators. 962 99

In the current study, we investigated the mechanism by which protein kinase C (PKC) regulates the expression of beta1-adrenergic receptor (beta1AR) mRNA in rat C6 glioma cells. Exposure of the cells to 4beta-phorbol-12-myristate-13-acetate (PMA), an activator PKC, resulted in a down-regulation of both beta1AR binding sites and mRNA levels in a time- and concentration-dependent manner. This effect was not observed with phorbol esters that do not activate PKC and was blocked by bisindolylmaleimide, a specific PKC inhibitor. Activation of PKC did not reduce the half-life of beta1AR mRNA but significantly decreased the activity of the beta1AR promoter, as determined by reporter analysis. A putative response element, with partial homology to a consensus cAMP response element, was identified by mutation analysis of the promoter at positions -343 to -336, relative to the translational start site. Mutation of this putative regulatory element, referred to as a beta1AR-PKC response element, completely blocked the PKC-mediated down-regulation of beta1AR promoter activity. Gel mobility shift analysis detected two specific bands when C6 cell extracts were incubated with a labeled DNA probe containing the beta1AR-PKC response element sequence. Formation of one of these bands was inhibited by an oligonucleotide probe containing a consensus CRE and disrupted by an antibody for cAMP response element binding protein. Based on these studies, we propose that the PKC-induced down-regulation of beta1AR gene transcription in C6 cells is mediated in part by a cAMP response element binding protein-dependent mechanism acting on a novel response element.
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PMID:Protein kinase C-mediated down-regulation of beta1-adrenergic receptor gene expression in rat C6 glioma cells. 965 85

Gel electrophoresis of DNA was used for estimation of DNA changes caused in C6 glioma cells by treatment with psychotropic drugs (imipramine, amitryptiline and fluoxetine). Some discrete bands containing a population of short DNA fragments appeared after 1 and 5 days of cultivation. Apoptotic DNA breaks were verified at single cell level using the TUNEL test in cells treated with fluoxetine.
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PMID:Estimation of apoptosis in C6 glioma cells treated with antidepressants. 972 8

Chronic exposure to ethanol increases transcription of the molecular chaperone Hsc70 in NG108-15 neuroblastoma X glioma cells. This and other ethanol-induced changes in gene expression may contribute to central nervous system tolerance and dependence in alcoholics. Here, we characterized sequences in the hsc70 promoter that are required for ethanol-induced transcriptional regulation. Deletion analysis of the hsc70 promoter showed that the 74-base pair region proximal to the transcription start site was sufficient for ethanol responsiveness. Point mutation or deletion of a consensus Spl-binding site at -67/-61 base pairs greatly reduced the induction by ethanol. Hsc70 promoter constructs with diminished ethanol responsiveness in NG108-15 cells similarly had decreased transcriptional activation by exogenous Sp1 in Drosophila SL2 cells. Some artificial promoter constructs containing multiple Sp1 sites were highly responsive to ethanol, but others were not, suggesting that the organization of the proximal promoter region was an additional factor that affected the ethanol response. Gel mobility shift analysis confirmed that an Sp1-like protein bound to the -67/-61 consensus Sp1 site. However ethanol exposure did not alter Sp1 DNA-binding activity. Together, our findings show that ethanol induction of Hsc70 requires a functional Sp1-binding site. Additional proximal promoter elements may also play a role in determining whether an Sp1-containing promoter will respond to ethanol.
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PMID:Characterization of promoter elements mediating ethanol regulation of hsc70 gene transcription. 1060 45

It was recently shown that the two transcripts encoding the isoforms of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP1 and CNP2) are differentially regulated during the process of oligodendrocyte maturation. In oligodendrocyte precursors, only CNP2 mRNA is present, whereas in differentiating oligodendrocytes, both CNP1 and CNP2 mRNAs are expressed. This pattern of CNP expression is likely due to stage-specific transcriptional regulation of the two CNP promoters during the process of oligodendrocyte differentiation. Here, we report the influence of increased intracellular cyclic AMP (cAMP) levels on the transcription of both CNP1 and CNP2 mRNAs in rat C6 glioma cells. We found that the transcription of CNP1 mRNA was significantly increased in comparison with that of CNP2 mRNA in cells treated with cAMP analogues to elevate intracellular cAMP levels. This up-regulation of CNP1 expression (a) is due to an increase of transcription, (b) requires de novo protein synthesis, and (c) requires the activity of protein kinase A. These results are physiologically significant and support the idea that a cAMP-mediated pathway is part of the molecular mechanisms regulating the expression of CNP1 in oligodendrocytes. The regulation of CNP1 promoter activity by cAMP was then investigated in stably transfected C6 cell lines containing various deletions of the CNP promoter directing the bacterial chloramphenicol acetyltransferase gene. We showed that the sequence between nucleotides -126 and -102 was essential for the cAMP-dependent induction of CNP1 expression. Gel retardation analysis showed that two protein-DNA complexes are formed between this sequence and nuclear factors from C6 cells treated or not treated with cAMP. This suggests that the induction of CNP1 mRNA transcription is not mediated by changes in binding of nuclear factors that interact directly with the -126/-102 sequence. Sequence analysis of this region revealed the presence of a putative activator protein-2 (AP-2) binding site. It is interesting that mutagenesis of this region resulted in a significant reduction in transcriptional responses to cAMP, implying a possible role for the AP-2 factor in the expression of CNP1. In addition, we have shown that putative binding sites for activator protein-4 and nuclear factor-1 adjacent to the AP-2 site are required for efficient induction of CNP1 expression by cAMP. Taken together, our results show that the cAMP-dependent accumulation of CNP1 mRNA appears to depend on the synergistic interaction of several regulatory elements.
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PMID:Transcriptional regulation of 2',3'-cyclic nucleotide 3'-phosphodiesterase gene expression by cyclic AMP in C6 cells. 1103 83

alphaB-Crystallin, a member of the small heat shock protein (HSP) family, accumulates in reactive astrocytes in a variety of pathological conditions. We previously reported the upregulation of alphaB-crystallin in response to high extracellular potassium concentration. In the present study, we investigated the regulatory mechanism of alphaB-crystallin expression by KCl. When human glioma U-251MG cells were exposed to continuous KCl treatment, induction of alphaB-crystallin mRNA was observed after 8 h and persisted for a few days. Functional promoter analysis using deletion and mutation constructs revealed that the proximal heat shock element (HSE-P), which contributes to heat shock induction in HeLa cells, is essential for transcriptional activation of the alphaB-crystallin gene by KCl in U-251MG cells. Gel mobility shift and antibody supershift assays showed that KCl induces the HSE-binding activity of heat shock factor (HSF) 2, while heat shock induces that of HSF1. This is the first demonstration that HSF2 can be activated by KCl and is involved in the upregulation of alphaB-crystallin gene expression in glial cells.
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PMID:Heat shock factor 2 is involved in the upregulation of alphaB-crystallin by high extracellular potassium. 1132 6

The expression of inducible nitric oxide synthase (NOS2) in glial cells is inhibited by neurotransmitters such as norepinephrine (NE) which elevate cAMP levels. We examined the molecular basis for this effect using a 2.2-kb fragment of the rat NOS2 promoter transfected into rat C6 glioma cells. Promoter activation (up to six-fold) by lipopolysaccharide (LPS) and interferon-gamma (IFNgamma) was reduced by NE, which alone had no effect. However, a promoter construct extending to bp -130 and containing the proximal nuclear factor-kappa B (NF-kappaB) binding site was minimally activated by LPS and cytokines, but activated up to three-fold by NE. Deletion analysis identified a 27-bp region (bp -187 to -160) as critical for mediating this suppressive effect. This region also enhanced promoter activation by LPS and cytokines, and prevented activation by NE alone. Gel shift analysis revealed constitutive binding to this region, and induction by NE of additional complexes which could be blocked by an antibody against CREB. NE also increased levels of the IkappaBalpha protein which could contribute to its suppressive effects. These results identify a critical role for this 27-bp region in regulation of NOS2 promoter activation and suppression by cAMP.
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PMID:A 27-bp region of the inducible nitric oxide synthase promoter regulates expression in glial cells. 1143 80

Overexpression of vascular endothelial growth factor (VEGF) is associated with disease progression in human glioblastomas. We recently showed that VEGF promoter activity is inversely correlated with tumor extracellular pH (pH(o)) in vivo in the human glioma (U87 MG) xenografts. Here we show that substitution of the neutral culture medium (pH 7.3) with acidic pH medium (pH 6.6) up-regulates VEGF mRNA and protein production in human glioblastoma cells as reflected by Northern blot analysis and enzyme-linked immunosorbent assay. Functional analysis of the VEGF promoter reveals that the sequence between -961 bp and -683 bp upstream of the transcription start site is responsible for the transcriptional activation of the VEGF gene by acidic pH. This region contains the binding site for AP-1. Consequently, AP-1 luciferase reporter gene was activated by acidic pH. Gel-shift analysis confirmed that AP-1 DNA binding activity is induced under acidic pH. While investigating the upstream signaling pathways, we found that ERK1/2 MAPK is activated and translocates to the nucleus to activate Elk-1, and inhibition of the activation of ERK by specific inhibitors of MEK1 blocks the up-regulation of VEGF by low pH. Dominant negative forms of Ras and Raf abolished the activation of VEGF promoter by acidic pH. These results show that acidic pH activates Ras and the ERK1/2 MAPK pathway to enhance VEGF transcription via AP-1, leading to increased VEGF production.
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PMID:Acidic extracellular pH induces vascular endothelial growth factor (VEGF) in human glioblastoma cells via ERK1/2 MAPK signaling pathway: mechanism of low pH-induced VEGF. 1174 77


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