Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0017636 (glioblastoma)
 18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ceramide has recently been regarded as a potential mediator of apoptosis. In the present study, the effects of Bcl-2 and Bax on the ceramide-mediated apoptotic pathways were examined in glioma cells overexpressing Bcl-2 or Bax. Etoposide, cisplatin and tumor necrosis factor-alpha induced apoptosis of C6 rat glioma cells which was associated with ceramide formation due to activation of neutral sphingomyelinase, followed by release of mitochondrial cytochrome c into the cytosol and activation of caspases-9 and -3. The growth of C6 cells stably overexpressing either Bcl-2 or Bax was almost equal to that of the vector-transfected cells. Bax overexpression enhanced etoposide-induced apoptosis through acceleration of cytochrome c release and caspases activation. However, Bax had no effect on ceramide formation. Similar findings were obtained in C6 cells and U87-MG human glioblastoma cells which were transiently overexpressed with Bax. In contrast, Bcl-2 overexpression resulted in a retardation of the apoptotic process via prevention of cytochrome c release and caspases activation, and ceramide formation was also blocked when Bcl-2 was highly overexpressed in glioma cells. In addition, transient overexpression of Bcl-xL also exerted inhibitory effects on ceramide formation and apoptotic cell death induced by etoposide. These results indicate that Bax promotes apoptosis regardless of ceramide formation and that Bcl-2 or Bcl-xL prevents ceramide formation by repressing neutral sphingomyelinase as well as ceramide-induced cytochrome c release. Oncogene (2000) 19, 3508 - 3520
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PMID:Influence of Bax or Bcl-2 overexpression on the ceramide-dependent apoptotic pathway in glioma cells. 1091 9

Tumor necrosis factor receptor type 1 (TNFR1) and c-Myc are important in signal transduction in tumor necrosis factor-alpha (TNF-alpha)-induced cytotoxicity, whereas activation of nuclear factor-kappa B (NF-kappa B) protects against TNF-alpha-induced apoptosis. This study investigated the expression of NF-kappa B, TNFR1, and c-Myc in human astrocytoma tissues by reverse transcriptase-polymerase chain reaction (PCR) and immunohistochemical analysis. TNFR1 messenger ribonucleic acid (mRNA) and c-Myc mRNA were frequently expressed in malignant astrocytomas, especially in glioblastomas, compared with low-grade astrocytomas by PCR analysis. TNFR1 and c-Myc mRNAs were barely detectable in normal brain tissues. NF-kappa B p50 and p65 subunit mRNAs were detected in various grades of astrocytomas, with frequent expression in malignant astrocytomas. The presence of activated NF-kappa B was confirmed by nuclear localization in neoplastic astrocytes as determined by immunohistochemistry. Both p50 and p65 subunits were inhomogeneously expressed in neoplastic astrocytes of glioblastoma, but only in a few scattered tumor cells in low-grade astrocytoma, and almost undetectable in normal brain tissues. These results indicate that TNFR1 and c-Myc are overexpressed in malignant astrocytomas, and this may increase the cellular sensitivity to the cytotoxic action of TNF-alpha. NF-kappa B p50 and p65 were simultaneously induced and activated in malignant astrocytomas. Our results suggest that the constitutive activation of NF-kappa B subunits in malignant astrocytoma, especially in glioblastoma, could be associated with the resistance to TNF-alpha immunotherapy, and indicates new therapeutic strategies for malignant astrocytomas.
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PMID:Expression of nuclear factor-kappa B, tumor necrosis factor receptor type 1, and c-Myc in human astrocytomas. 1138 77

A series of novel, synthetic compounds containing lipids linked to a phosphate-containing acyclic backbone are shown to have similar biological properties to lipopolysaccharide (LPS). These compounds showed intrinsic agonistic properties when tested for their ability to stimulate tumor necrosis factor-alpha in human whole blood and interleukin-6 in U373 human glioblastoma cells without added LPS coreceptor CD14. The presence of the LPS antagonist E5564 completely blocked responses, suggesting that the novel compounds and LPS share a common mechanism of cell activation. Stereoselectivity of the molecules was observed in vitro; compounds with an R,R,R,R-configuration were strongly agonistic, whereas compounds with an R,S,S,R-configuration were much weaker in their activity on human whole blood and U373 cells. We also tested the effect of the compounds in cells transfected with the LPS receptor Toll-like receptor 4 (TLR4), with similar results, further supporting a shared mechanism with LPS. This was confirmed in vivo where the agonists failed to elicit cytokine responses in C3H/HeJ mice lacking TLR4 signaling. Because LPS-like molecules enhance immune responses, the compounds were mixed with tetanus toxoid and administered to mice in an immunization protocol to test for adjuvant activity. They enhanced the generation of specific antibodies against tetanus toxoid. Our results indicate that these unique compounds behave as agonists of TLR4, resulting in responses similar to those elicited by LPS. They display adjuvant activity in vivo and may be useful for the development of vaccine therapies.
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PMID:A novel class of endotoxin receptor agonists with simplified structure, toll-like receptor 4-dependent immunostimulatory action, and adjuvant activity. 1180 29

Immunotherapies, although promising in preclinical studies, have not yet enhanced the survival of patients with glioblastomas. To further understand the immunobiology of glioblastomas in clinical settings, we examined 53 cytokine or cytokine receptor transcripts in 12 human glioblastomas and 6 human glioblastoma cell lines and correlated the findings with the degree of inflammation. Multi-probe RNase protection assays were used to examine Th1, Th2, and Th3 cytokine and cytokine receptor expression. Th2 [interleukin (IL)-6, leukemia inhibitory factor and oncostatin M] and Th3 (transforming growth factor-beta1, 2, 3) cytokine and their receptor transcripts were strongly expressed in almost all glioblastomas and glioma cell lines. Two other Th2 cytokine receptor subunit transcripts (IL-4Ralpha and IL-13Ralpha) were also commonly detected. In contrast, although Th1 cytokine receptors tumor necrosis factor (TNF) RI, interferon (IFN)-gammaRalpha, IFN-gammaRbeta, were detected, their cytokines (IFN-gamma, TNF-alpha, lymphotoxin-alpha) were not. Transcripts for IL-2 family cytokine (IL-2, IL-7, IL-9, IL-15) and receptors (IL-2Ralpha, IL-2Rbeta, gammac, IL-7Ralpha, IL-9Ralpha, IL15Ralpha) and IL-12 family cytokine (IL-12p40) and receptors (IL-12Rbeta1 and IL-12beta2) were essentially absent in both tumors and cell lines. Immunohistochemical methods showed sparse T lymphocyte infiltrates and numerous microglia in the glioblastomas. This pattern indicates an 'immunosuppressive status' in glioblastomas and could account for the failure of immunotherapy in such tumors.
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PMID:Cytokine and cytokine receptor mRNA expression in human glioblastomas: evidence of Th1, Th2 and Th3 cytokine dysregulation. 1181 Jan 84

Interactions of CD70, a tumor necrosis factor-related cell surface ligand and its receptor, CD27, are thought to play an important role for T-, B-, and natural killer-cell activation. However, ligation of CD27 can also induce apoptosis. Human glioblastoma is paradigmatic for cancer-associated immunosuppression. We identified CD70 as a radioinducible gene in U87 MG glioma cells. A screening of a panel of human glioma cell lines revealed that 11 of 12 cell lines expressed CD70 mRNA and protein. Two human neuroblastoma cell lines did not express CD70. CD70 mRNA expression was enhanced by irradiation in 8 of 12 glioma cell lines in a p53-independent manner. No alteration in CD70 expression was observed after glioma cell exposure to cytotoxic drugs such as lomustine. CD70 protein was also detected by immunocytochemistry in 5 of 12 glioblastomas and 3 of 4 anaplastic astrocytomas in vivo. CD27 expression was not detected in any glioma cell line, and there was no evidence for autocrine or backward signaling of the CD70 system in human glioma cells. Unexpectedly, CD70 expressed on glioma cells did not increase the immunogenicity of glioma cells in vitro. In contrast, CD70-positive glioma cells induced apoptosis in peripheral blood mononuclear cells (PBMCs) in a CD70-dependent manner. Neutralization of CD70 expressed on glioma cells prevented apoptosis and enhanced the release of tumor necrosis factor-alpha in cocultures of glioma cells and PBMCs. The effects of CD70-expressing glioma cells on PBMCs were mimicked by agonistic CD27 antibodies. Conversely, the shedding of CD27 by PBMCs was identified as a possible escape mechanism from glioma cell-induced CD70-dependent apoptosis. Thus, induction of B-cell and T-cell apoptosis via interactions of CD70 expressed on glioma cells and CD27 expressed on B and T cells may be a novel way for the immune escape of malignant gliomas.
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PMID:Identification of CD70-mediated apoptosis of immune effector cells as a novel immune escape pathway of human glioblastoma. 1198 Jun 54

A major concern in cancer therapy is resistance of tumors such as glioblastoma to current treatment protocols. Here, we report that transfer of the gene encoding second mitochondria-derived activator of caspase (Smac) or Smac peptides sensitized various tumor cells in vitro and malignant glioma cells in vivo for apoptosis induced by death-receptor ligation or cytotoxic drugs. Expression of a cytosolic active form of Smac or cell-permeable Smac peptides bypassed the Bcl-2 block, which prevented the release of Smac from mitochondria, and also sensitized resistant neuroblastoma or melanoma cells and patient-derived primary neuroblastoma cells ex vivo. Most importantly, Smac peptides strongly enhanced the antitumor activity of Apo-2L/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in an intracranial malignant glioma xenograft model in vivo. Complete eradication of established tumors and survival of mice was only achieved upon combined treatment with Smac peptides and Apo2L/TRAIL without detectable toxicity to normal brain tissue. Thus, Smac agonists are promising candidates for cancer therapy by potentiating cytotoxic therapies.
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PMID:Smac agonists sensitize for Apo2L/TRAIL- or anticancer drug-induced apoptosis and induce regression of malignant glioma in vivo. 1211 45

In contrast to nuclear factor-kappaB (NF-kappaB) activation by tumor necrosis factor-alpha (TNF-alpha), the specific processes involved in the activation of this transcription factor by ionizing radiation (IR) have not been completely defined. According to the classical paradigm, a critical event in NF-kappaB activation is the degradation of I(kappa)B(alpha). Data presented herein show that, in contrast to treatment with TNF-alpha, IR-induced NF-kappaB activation was not accompanied by degradation of I(kappa)B(alpha) in the U251 glioblastoma cell line as determined in whole cell lysates. However, treatment with the proteosome inhibitor MG-132 inhibited NF-kappaB activation induced by IR, suggesting that I(kappa)B(alpha) degradation was a critical event in this process. To reconcile these results, U251 cell lysates were separated into soluble and insoluble fractions and I(kappa)B(alpha) levels evaluated. Although I(kappa)B(alpha) was found in both subcellular fractions, treatment with IR resulted in the degradation of I(kappa)B(alpha) only in the insoluble fraction. Further subcellular fractionation suggested that the IR-sensitive, insoluble pool of I(kappa)B(alpha) was associated with the plasma membrane. These data suggest that the subcellular location of I(kappa)B(alpha) is a critical determinant in IR-induced NF-kappaB activation.
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PMID:Radiation-induced activation of nuclear factor-kappaB involves selective degradation of plasma membrane-associated I(kappa)B(alpha). 1238 47

Current therapies for gliomas fail to address their highly infiltrative nature. Standard treatments often leave behind microscopic neoplastic reservoirs, resulting in eventual tumor recurrence. Neural stem cells (NSCs) are capable of tracking disseminating glioma cells. To exploit this tropism to develop a therapeutic strategy that targeted tumor satellites, we inoculated human glioblastoma xenografts with tumor necrosis factor-related apoptosis-inducing ligand-secreting NSCs. This resulted in the dramatic induction of apoptosis in treated tumors and tumor satellites and was associated with significant inhibition of tumor growth. These results add credence to the potential of NSCs as therapeutically effective delivery vehicles for the treatment of intracranial glioma.
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PMID:Induction of glioblastoma apoptosis using neural stem cell-mediated delivery of tumor necrosis factor-related apoptosis-inducing ligand. 1249 52

Glioblastoma multiforme comprises the majority of human brain tumors. Patients with glioblastoma multiforme have poor survival rates, with an average life expectancy of <1 year. To assess possible mechanisms and to potentially target invasive glioma cells, we previously measured the gene expression profiles of glioma cells under migration-activated or passive states. One of the genes identified was Fn14, which encodes a cell surface receptor for the tumor necrosis factor superfamily member named TWEAK. In this study, we show that Fn14 gene expression is induced in migration-activated glioma cells in vitro and significantly increases according to tumor grade in vivo (P < 0.01), with highest levels in glioblastoma tissue specimens. The in situ expression pattern of Fn14 mRNA and protein was confined to primary glioma cells and the vascular endothelium, with no detection in adjacent normal brain. Conversely, TWEAK mRNA levels are low in glioblastoma samples relative to normal brain tissue. In addition, activation of the Fn14 receptor by addition of recombinant TWEAK resulted in increased glioma cell migration in vitro. These results suggest a positive role for TWEAK and Fn14 in glioma progression and indicate that Fn14 gene expression may serve as a marker for invasive glioma cells.
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PMID:The human Fn14 receptor gene is up-regulated in migrating glioma cells in vitro and overexpressed in advanced glial tumors. 1265 23

This study examines the signaling mechanism by which cilostazol prevents neuronal cell death. Cilostazol ( approximately 0.1-100 microM) prevented tumor necrosis factor-alpha (TNF-alpha)-induced decrease in viability of SK-N-SH and HCN-1A cells, which was antagonized by 1 microM iberiotoxin, a maxi-K channel blocker. TNF-alpha did not suppress the viability of the U87-MG cell, a phosphatase and tensin homolog deleted from chromosome 10 (PTEN)-null glioblastoma cell, but it did decrease viability of U87-MG cells transfected with expression vectors for the sense PTEN, and this decrease was also prevented by cilostazol. Cilostazol as well as 1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one (NS-1619) and (3S)(+)-(5-chloro-2-methoxyphenyl)-1,3-dihydro-3-fluoro-6-(trifluoromethyl)-2H-indole-2-one (BMS 204352), maxi-K channel openers, prevented increased DNA fragmentation evoked by TNF-alpha, which were antagonizable by iberiotoxin. TNF-alpha-induced increased PTEN phosphorylation and decreased Akt/cyclic AMP response element-binding protein (CREB) phosphorylation were significantly prevented by cilostazol, those of which were antagonized by both iberiotoxin and paxilline, maxi-K channel blockers. The same results were evident in U87-MG cells transfected with expression vectors for sense PTEN. Cilostazol increases the K+ current in SK-N-SH cells by activating maxi-K channels without affecting the ATP-sensitive K+ channel. Thus, our results for the first time provide evidence that cilostazol prevents TNF-alpha-induced cell death by suppression of PTEN phosphorylation and activation of Akt/CREB phosphorylation via mediation of the maxi-K channel opening.
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PMID:Cilostazol prevents tumor necrosis factor-alpha-induced cell death by suppression of phosphatase and tensin homolog deleted from chromosome 10 phosphorylation and activation of Akt/cyclic AMP response element-binding protein phosphorylation. 1280 96


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