UMLS:C0017636 - FACTA Search

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Query: UMLS:C0017636 (glioblastoma)
18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human glioblastoma cells secrete a factor termed glioblastoma derived T cell suppressor factor (G-TsF) or transforming growth factor beta 2 (TGF-beta 2) which inhibits the response of T cells to mitogenic or antigenic stimulation. In the present study we isolated the promoter region of the G-TsF/TGF-beta 2 gene. The promoter region shares no homology to the promoter of the TGF-beta 1 or the 5' region of the TGF-beta 3 gene and harbours several familiar DNA motifs, including the cytokine-1 region, an octamer-like sequence, Sp1- and AP-2-like elements and a putative NF-kappa B site. In contrast to the TGF-beta 1 gene, the G-TsF/TGF-beta 2 gene contains three TATA-like sequences but lacks an AP-1 site. To understand the cell type specificity of expression of G-TsF/TGF-beta 2, the individual contribution of the DNA elements detected in the promoter has to be analysed in further studies.
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PMID:Sequence analysis of the promoter region of the glioblastoma derived T cell suppressor factor/transforming growth factor (TGF)-beta 2 gene reveals striking differences to the TGF-beta 1 and -beta 3 genes. 222 34

The c-kit proto-oncogene encodes a tyrosine kinase receptor for stem cell factor and plays a critical role in the growth and differentiation of various types of cells including hematopoietic stem cells. To investigate the mechanisms of its transcriptional regulation, we isolated the 5' flanking region of the human c-kit gene and characterized its promoter activity in hematopoietic cells. Nucleotide sequence analysis revealed that the 1.2 kb 5' flanking region lacked a typical "TATA box," but had a relatively high G + C content and four potential Sp1-binding sites. Putative binding sites for AP-2, basic helix-loop-helix proteins, Ets-domain proteins, Myb and GATA-1 were also found. Primer extension and S1 nuclease protection analyses of hematopoietic cells indicated that the major transcription start sites are 62 bp and 58 bp upstream of the translation start site. Essentially the same start sites were detected in non-hematopoietic cells such as small cell lung carcinoma and glioblastoma: this single promoter in c-kit is different from the multiple promoter system of c-fms, a c-kit-related gene, in which at least two promoters are differently used in hematopoietic and non-hematopoietic cells. An analysis of the c-kit 5' flanking region using the bacterial chloramphenicol acetyltransferase gene (CAT assay) in human erythroleukemia HEL cells, which express the endogenous c-kit mRNA at high levels, showed that a region from -180 to -22 is important for the expression of the c-kit gene. In addition, a negative regulatory element(s) is suggested to be involved in the regulation of the c-kit gene expression in mammals.
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PMID:Characterization of the promoter region of the human c-kit proto-oncogene. 750 48

The proteolipid protein (PLP) gene encodes the main integral protein of the myelin membrane of the central nervous system. The expression of the gene is regulated in a cell- and development-specific manner. Comparison of approximately 1.5 kb of the upstream noncoding region from man, mouse, and rat gene revealed an extensive sequence identity of about 95% between -250 and +100 (the most upstream transcription start site is defined as +1) but only about 50% identity further upstream. To define potential cis-acting elements in the promoter of the mouse PLP gene the upstream region was studied by transfection of C6 glioblastoma cells and CHO fibroblasts with various 5' deletion constructs fused to the reporter gene luciferase. We localized a promoter at position -184 to +90, which is active in both cell lines. Analysis of this region by DNase I foot-printing experiments and band shift analysis with nuclear extracts from myelinating brain, liver, C6, and CHO cells shows the binding of several different proteins to the promoter region. One brain-specific and two ubiquitous factors bound to the sequence AAGGGGAGGAG (DR1/2 box). This motif is also present in the upstream region of other myelin-specific genes and in some variants of the glia cell-specific virus JC. The factors bound with similar affinity to a Sp1-binding site. Therefore one of the ubiquitous factors seems to be Sp1 suggesting that Sp1 may play a role in the transcriptional regulation of the PLP gene. It has been shown that the DR1/2 box-binding factors are Zn(2+)-dependent. By Southwestern blotting it has been demonstrated that the DR1/2 box binds a protein of about 66 kDa that is enriched in brain.
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PMID:Characterization of a brain-specific Sp1-like activity interacting with an unusual binding site within the myelin proteolipid protein promoter. 769 80

Expression of the human monocyte chemoattractant protein-1 (hMCP-1) is ubiquitous in various cell types and is increased by a wide variety of stimuli. We initially found that the effects of various stimuli, including IL-1 beta, TNF-alpha, and 2-O-tetradecanoylphorbol 13-acetate, on the expression of hMCP-1 mRNA were quite different among A172 glioblastoma cells, HT1080 fibrosarcoma cells, and SKLMS1 leiomyosarcoma cells. These findings suggested that hMCP-1 expression is regulated both in a stimulus-specific and a tissue-specific manner. To elucidate the mechanism underlying this stimulus-specific and tissue-specific regulation, we isolated a hMCP-1 5'-flanking genomic DNA fragment and sequenced it extensively up to bp 3011 upstream from the transcriptional start site. Among many putative cis-elements, we identified two cis-elements critical for the transcription of the hMCP-1 gene. The first element is a remote kappa B binding site located far upstream between bp -2612 and -2603 that was important for IL-1 beta-, TNF-alpha-, and 2-O-tetradecanoylphorbol 13-acetate-induced enhancer activity. Mutation at the kappa B consensus site resulted in a complete loss of these stimulus-induced enhancer activities. The second element is a GC box located between bp -64 and -59 that was important for the maintenance of basal transcriptional activity. Overexpression of rSp1 resulted in increased hMCP-1 transcriptional activity, possibly suggesting the role of Sp1 in controlling basal hMCP-1 transcription via this GC box. These results together indicate that hMCP-1 expression is controlled by at least two distinct regulatory elements: a kappa B site and a GC box that seem to be associated with stimulus-specific and tissue-specific regulation, respectively.
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PMID:NF-kappa B and Sp1 regulate transcription of the human monocyte chemoattractant protein-1 gene. 805 10

Synthetic oligodeoxyribonucleotides (ODNs) designed to selectively inhibit the transcription or translation of specific genes are being used to modulate the activity of the targeted gene. Because multiple copies of mRNA can be transcribed from one actively expressed gene, ODNs that target double-stranded DNA and form triple helices upon binding with the gene itself have an advantage over ODNs that target the gene product (mRNA) in an antisense fashion. For the present studies, we designed four different triple helix-forming phosphodiester ODNs (TFOs) targeted to the tumor necrosis factor (TNF) gene and examined their effect on production of TNF and on cellular growth of tumors in which TNF acts as an autocrine growth factor. The ODNs J-109-50 and J-108-57 were designed to interact with polypurine oligonucleotides corresponding to the binding sites for nuclear factors kB (-237 to -208) and Sp1 (-58 to -33), respectively; J111-51 was designed to interact with a polypurine oligonucleotide in the third intron (+1429 to +1456) of the TNF gene. To enhance the cellular penetration and prevent degradation by cellular nucleases, the TFOs were modified at their 3' ends by either a cholesterol side chain or a propanolamine blocking group. Treatment of the human promonocytic cell line THP-1 with TNF-TFOs at a nontoxic concentration (2 microM) reduced the production of TNF. All of the TNF-TFOs tested were effective, and control-irrelevant TFOs were ineffective in inhibiting TNF production. The activity of the most efficacious TNF-TFOs also correlated with a decrease in TNF mRNA as observed by using reverse transcriptase PCR assays. In several tumors in which TNF acts as an autocrine growth factor, we examined the antiproliferative activity of J111-51. We found that in the human glioblastoma tumor cell line U-251, TNF-induced growth was blocked by J111-51 in a dose-dependent manner. Thus, overall results demonstrate that oligonucleotides directed to the specific regions of TNF can be designed, which may have a potential in cancer therapy.
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PMID:Triple helix-forming oligodeoxyribonucleotides targeted to the human tumor necrosis factor (TNF) gene inhibit TNF production and block the TNF-dependent growth of human glioblastoma tumor cells. 891 51

The aquaporin-4 (AQP4) gene encodes proteins of approximately 31 and 34 kDa with distinct N-terminal sequences. Both protein isoforms are expressed in brain, whereas mainly the smaller isoform is found in other tissues. We isolated the promoter sequences upstream of exon 0 (encoding the longer isoform) and exon 1 (encoding the shorter isoform). The exon 0 promoter region contained multiple TATA and CCAAT boxes and Sp1, AP1, and E-box elements; the exon 1 promoter lacked a CCAAT box but contained a TATA box and AP1, AP2, and E-box elements. Utilizing the CAT reporter assay, promoter activities were 7- to 9-fold greater for fragments from exon 1 vs exon 0 in human glioblastoma cells (SF-126, U-87 MG) and 11- to 13-fold greater in kidney cells (MDCK and LLC-PK1). Promoter deletion analysis indicated a strong suppressor element located just upstream of nucleotide -428 in the exon 0 promoter. RT-PCR analysis of human brain and kidney cDNAs confirmed much higher relative expression of transcript containing exon 0 vs exon 1 in brain. These results indicate differential transcriptional regulation of two AQP4 isoforms and suggest that tissue-specific factors regulate their relative expression.
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PMID:Isolation and functional analysis of alternative promoters in the human aquaporin-4 water channel gene. 967 32

It has been shown that the human immunodeficiency virus type 1 (HIV-1) Tat protein can specifically enhance expression and release of monocyte chemoattractant protein 1 (MCP-1) from human astrocytes. In this study, we show evidence that Tat-induced MCP-1 expression is mediated at the transcriptional level. Transient transfection of an expression construct encoding the full-length Tat into the human glioblastoma-astrocytoma cell line U-87 MG enhances reporter gene activity from cotransfected deletion constructs of the MCP-1 promoter. HIV-1 Tat exerts its effect through a minimal construct containing 213 nucleotides upstream of the translational start site. Site-directed mutagenesis studies indicate that an SP1 site (located between nucleotides -123 and -115) is critical for both constitutive and Tat-enhanced expression of the human MCP-1 promoter, as mutation of this SP1 site significantly diminished reporter gene expression in both instances. Gel retardation experiments further demonstrate that Tat strongly enhances the binding of SP1 protein to its DNA element on the MCP-1 promoter. Moreover, we also observe an increase in the binding activities of transcriptional factors AP1 and NF-kappaB to the MCP-1 promoter following Tat treatment. Mutagenesis studies show that an upstream AP1 site and an adjacent NF-kappaB site (located at -128 to -122 and -150 to -137, respectively) play a role in Tat-mediated transactivation. In contrast, a further upstream AP1 site (-156 to -150) does not appear to be crucial for promoter activity. We postulate that a Tat-mediated increase in SP1 binding activities augments the binding of AP1 and NF-kappaB, leading to synergistic activation of the MCP-1 promoter.
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PMID:The human immunodeficiency virus type 1 Tat protein up-regulates the promoter activity of the beta-chemokine monocyte chemoattractant protein 1 in the human astrocytoma cell line U-87 MG: role of SP-1, AP-1, and NF-kappaB consensus sites. 1064 32

Cathepsin B expression is increased at both the mRNA and protein levels in a wide variety of tumors. The mechanisms responsible for this regulation are not well elucidated. We have isolated a 2.2-kb cathepsin B genomic fragment that contains the 5'-flanking region of the cathepsin B gene. Using reporter gene analysis in human glioblastoma U87MG cells, we have mapped a 228-bp fragment (-172 to +56) having high promoter activity. This promoter region has a high G+C content; contains potential Spl, Ets, and USF binding motifs; and lacks canonical TATA and CAAT boxes immediately upstream of the major transcriptional initiation site. Cotransfection experiments demonstrated that Spl and Ets1 could trans-activate cathepsin B transcription, whereas Ets2 could not. Electrophoretic mobility shift assays and supershift assays revealed that three of the four putative Sp1 sites in this promoter region form a specific complex containing the Sp1 transcription factor. Mutating all four of the Spl binding sites individually markedly reduced the promoter activity of transfected reporter genes in U87 cells. Cotransfection of this cathepsin B promoter construct with Spl family expression vectors in Schneider's Drosophila line 2 (SL2) cells demonstrated that Spl and Sp3, but not Sp4, activated cathepsin B transcription. Taken together, these results suggest that Sp1, Sp3, and Ets1 are important factors in cathepsin B transcription. The regulation of cathepsin B transcription by Sp1- and Sp1-related factors is mediated through multiple GC boxes.
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PMID:Transcription of human cathepsin B is mediated by Sp1 and Ets family factors in glioma. 1070 74

We have been developing synthetic gene promoters responsive to clinical doses of ionizing radiation (IR) for use in suicide gene therapy vectors. The crucial DNA sequences utilized are units with the consensus motif CC(A/T)(6)GG, known as CArG elements, derived from the IR-responsive Egr1 gene. In this study we have investigated the parameters needed to enhance promoter activation to radiation. A series of plasmid vectors containing different enhancer/promoters were constructed, transiently transfected into tumor cells (MCF-7 breast adenocarcinoma and U-373MG glioblastoma) and expression of a downstream reporter assayed. Results revealed that increasing the number of CArG elements, up to a certain level, increased promoter radiation-response; from a fold-induction of 1.95 +/- 0.17 for four elements to 2.74 +/- 0.17 for nine CArGs of the same sequence (for MCF-7 cells). Specific alteration of the core A/T sequences caused an even greater positive response, with fold-inductions of 1.71 +/- 0.23 for six elements of prototype sequence compared with 2.96 +/- 0.52 for one of the new sequences following irradiation. Alteration of spacing (from six to 18 nucleotides) between elements had little effect, as did the addition of an adjacent Sp1 binding site. Combining the optimum number and sequence of CArG elements in an additional enhancer was found to produce the best IR induction levels. Furthermore, the improved enhancers also performed better than the previously reported prototype when used in in vitro and in vivo experimental GDEPT. We envisage such enhancers will be used to drive suicide gene expression from vectors delivered to a tumor within an irradiated field. The modest, but tight expression described in the present study could be amplified using a molecular 'switch' system as previously described using Cre/LoxP. In combination with targeted delivery, this strategy has great potential for significantly improving the efficacy of cancer treatment in the large number of cases where radiotherapy is currently employed.
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PMID:Optimizing radiation-responsive gene promoters for radiogenetic cancer therapy. 1236 5

We have previously isolated the human cathepsin B promoter and shown that Sp1 and Ets factors are involved in the regulation of cathepsin B expression. Using mutagenesis, transient transfection and electrophoretic mobility shift assays (EMSAs), we further identified regulatory factors that mediate cathepsin B transcription in U87 human glioblastoma cells. An E-box element (CACGTG) adjacent to the transcription initiation site (at nucleotides -7 to -2) was found to be indispensable for cathepsin B promoter activity. Mutation of this E-box element in both pSCB2, a promoter construct with high promoter activity, and pSCB6, a construct with basal promoter activity, led to a 90% decrease in promoter activity in U87 cells. EMSAs demonstrated that upstream stimulatory factor 1 (USF-1) and upstream stimulatory factor 2 (USF-2) bound to the E-box as a heterodimer. Chromatin immunoprecipitation assays revealed that both USF-1 and USF-2 were associated with the cathepsin B promoter. The roles of USF-1 and USF-2 in the regulation of cathepsin B expression were demonstrated by (i) co-transfection experiments showing that USF-1 or USF-2 increased promoter activity by 2.5-fold individually and by 3.4-fold together; (ii) co-transfection of pSCB6 with pUSF-2deltaN (a dominant negative USF-2 expression plasmid) resulting in an 80% decrease in promoter activity; and (iii) mutation of the E-box element (from 5'-CACGTG to 5'-CGCGTT in the pSCB6 basal promoter construct) abolishing transactivation of cathepsin B by USF-1 and USF-2. These results collectively indicate that an E-box at nucleotides -7 to -2 of the cathepsin B promoter is critical to the expression of cathepsin B and that binding of USF-1 and USF-2 to this E-box can regulate cathepsin B promoter activity.
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PMID:Transcription of cathepsin B in glioma cells: regulation by an E-box adjacent to the transcription initiation site. 1466 84

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