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

The early growth response-1 gene (egr-1) encodes a zinc-finger transcription factor Egr-1 and is rapidly inducible by a variety of extracellular stimuli. Anisomycin (ANX), a protein synthesis inhibitor, stimulates mitogen-activated protein kinase (MAPK) pathways and thereby causes a rapid induction of immediate-early response genes. We found that anisomycin treatment of U87MG glioma cells resulted in a marked, time-dependent increase in levels of Egr-1 protein. The results of Northern blot analysis and reporter gene assay of egr-1 gene promoter (Pegr-1) activity indicate that the ANX- induced increase in Egr-1 occurs at the transcriptional level. Deletion of the serum response element (SRE) in the 5'-flanking region of egr-1 gene abolished ANX-induced Pegr-1 activity. ANX induced the phosphorylation of the ERK1/2, JNK, and p38 MAPKs in a time-dependent manner and also induced transactivation of Gal4-Elk-1, suggesting that Elk-1 is involved in SRE-mediated egr-1 transcription. Transient transfection of dominant-negative constructs of MAPK pathways blocked ANX-induced Pegr-1 activity. Furthermore, pretreatment with specific MAPK pathway inhibitors, including the MEK inhibitor U0126, the JNK inhibitor SP600125, and the p38 kinase inhibitor SB202190, completely inhibited ANX-inducible expression of Egr-1. Taken together, these results suggest that all three MAPK pathways play a crucial role in ANX-induced transcriptional activation of Pegr-1 through SRE-mediated transactivation of Elk-1.
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PMID:The translation inhibitor anisomycin induces Elk-1-mediated transcriptional activation of egr-1 through multiple mitogen-activated protein kinase pathways. 1720 44

Basic fibroblast growth factor (bFGF) and transforming growth factor-beta1 (TGF-beta1) play an important role in proliferation, differentiation, and survival of malignant gliomas and in normal glial cell biology. Because of these critical roles, potential interactions between these key growth factors were investigated. We previously demonstrated that bFGF potently stimulates TGF-beta1 release from rat glioma cells. The purpose of the present study was to elucidate the mechanism(s) of this regulatory effect, establish its functional importance, and examine whether it extends to nontransformed rat hypothalamic astrocytes (RHA). The results revealed that RHA express the high-affinity FGF(1-4) receptors, and similarly to glioma cells, bFGF stimulated TGF-beta1 release in an isoform-specific manner. A mediatory role for ERK signaling in bFGF-induced TGF-beta release was suggested by the fact that MEK1 inhibition prevented this effect. Additionally, bFGF enhanced MEK1/2 phosphorylation and ERK activation/nuclear translocation, which culminated in increased activity of AP-1-mediated gene transcription. bFGF markedly induced TGF-beta1 mRNA levels in an isoform-specific manner, an effect that was dependent on MEK/ERK/AP-1 signaling. Functionally, bFGF-induced proliferation of glioma cells was attenuated by MEK/ERK inhibition or immunoneutralization of TGF-beta1, suggesting that this pathway may have important implications for brain tumor progression.
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PMID:Induction of transforming growth factor-beta1 by basic fibroblast growth factor in rat C6 glioma cells and astrocytes is mediated by MEK/ERK signaling and AP-1 activation. 1733 76

Treatment of rat glioma C6 cells with the beta-receptor agonist isoproterenol induces a massive increase in cAMP. Concomitantly the cells change their morphology from a fibroblast-type to an astrocyte-like (stellated) cell shape. The stellated morphology can be completely reverted by thrombin and sphingosine-1-phosphate (S-1-P) but also to a certain extent by clinical concentrations of volatile anesthetics. The anesthetic-induced reversion of the stellated cell shape seems to be mediated by a number of cellular alterations. Central to the effect is most likely a RhoA/Rho-kinase activation, but also the MAPKK/MEK and the Akt/protein kinase B pathway are activated by the anesthetics. With the use of specific inhibitors we were able to show that activation of the MAPKK/MEK pathway inhibits, whereas activation of the Akt/protein kinase B pathway stimulates the reversal of the stellated cell shape by the anesthetics. In summary, volatile anesthetics affect the morphology of rat glioma C6 cells by activation of the RhoA/Rho kinase, the MAPKK/MEK, and the Akt/protein kinase B signaling pathways.
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PMID:Volatile anesthetics affect the morphology of rat glioma C6 cells via RhoA, ERK, and Akt activation. 1749 63

Urokinase plasminogen activator (uPA) and its receptor (uPAR) play a major role in invasion and proliferation. A growing body of evidence has suggested that the uPA system promotes tumor metastasis by several different mechanisms, and not just solely by breaking down the ECM. In this study we have used RNAi-mediated simultaneous down-regulation of uPAR and uPA to determine the signaling pathway molecules and caspase-mediated apoptosis. From our in vitro experiments, we have observed that plasmid-based RNAi-mediated down-regulation of uPAR and uPA in SNB19 human glioma cells caused a decrease in the levels of uPAR protein and uPA enzyme activities. In addition, we observed a decrease in the phosphorylation of the Ras-activated pathway molecules such as FAK, p38MAPK, JNK and ERK1/2, as well as the MEK-activated phosphatidylinositol 3-kinase (PI3k) pathway, and also retarded the dephosphorylation of p-AKTser473 and p-mTORser2448, indicative of a feedback signaling mechanism of the uPAR-uPA system. Activation of caspase 8 accompanied by the release of cytochrome c and cleavage of PARP was also observed and indicative of Fas-mediated apoptosis. The use of FMK-VAD-FAK peptides coupled with FITC indicated activation of polycaspases, which was accompanied by the presence of fragmented nuclei. Our studies provide evidence for the presence of a feedback response of the uPAR-uPA system indicative of the multifaceted role of uPAR, and also the therapeutic potential of simultaneously targeting uPAR and uPA in cancer patients.
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PMID:Down-regulation of uPAR and uPA activates caspase-mediated apoptosis and inhibits the PI3K/AKT pathway. 1754 1

There has been considerable interest in recent years in the anti-tumor activities of flavonoids. Quercetin, a ubiquitous bioactive flavonoid, can inhibit proliferation and induce apoptosis in a variety of cancer cells. However, the precise molecular mechanism by which quercetin induces apoptosis in cancer cells is poorly understood. The present study was undertaken to examine the effect of quercetin on cell viability and to determine its underlying mechanism in human glioma cells. Quercetin resulted in loss of cell viability in a dose- and time-dependent manner and the decrease in cell viability was mainly attributed to cell death. Quercetin did not increase reactive oxygen species (ROS) generation and the quercetin-induced cell death was also not affected by antioxidants, suggesting that ROS generation is not involved in loss of cell viability. Western blot analysis showed that quercetin treatment caused rapid reduction in phosphorylation of extracellular signal-regulated kinase (ERK) and Akt. Transient transfection with constitutively active forms of MEK and Akt protected against the quercetin-induced loss of cell viability. Quercetin-induced depolarization of mitochondrial membrane potential. Caspase activity was stimulated by quercetin and caspase inhibitors prevented the quercetin-induced loss of cell viability. Quercetin resulted in a decrease in expression of survivin, antiapoptotic proteins. Taken together, these findings suggest that quercetin results in human glioma cell death through caspase-dependent mechanisms involving down-regulation of ERK, Akt, and survivin.
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PMID:Underlying mechanism of quercetin-induced cell death in human glioma cells. 1832 95

We previously reported that serotonin (5-HT) increased glial cell line-derived neurotrophic factor (GDNF) release in a 5-HT(2) receptor (5-HT(2)R) and mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK)-dependent manner in rat C6 glioma cells (C6 cells), a model of astrocytes. We herein found that 5-HT-induced rapid ERK phosphorylation was blocked by 5-HT(2)R antagonists in C6 cells. We therefore examined 5-HT-induced ERK phosphorylation to reveal the mechanism of 5-HT-induced GDNF mRNA expression. As 5-HT-induced ERK phosphorylation was blocked by inhibitors for Galpha(q/11) and fibroblast growth factor receptor (FGFR), but not for second messengers downstream of Galpha(q/11), 5-HT(2)R-mediated FGFR transactivation was suggested to be involved in the ERK phosphorylation. Although FGFR1 and 2 were functionally expressed in C6 cells, 5-HT selectively phosphorylated FGFR2. Indeed, small interfering RNA for FGFR2, but not for FGFR1, blocked 5-HT-induced ERK phosphorylation. As Src family tyrosine kinase inhibitors and microtubule depolymerizing agents blocked 5-HT-induced FGFR2 phosphorylation, Src family tyrosine kinase and stabilized microtubules were suggested to act upstream of FGFR2. Finally, 5-HT-induced GDNF mRNA expression was also inhibited by the blockade of 5-HT(2)R, FGFR, and Src family tyrosine kinase. In conclusion, our findings suggest that 5-HT induces GDNF mRNA expression via 5-HT(2)R-mediated FGFR2 transactivation in C6 cells.
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PMID:Serotonin (5-HT) induces glial cell line-derived neurotrophic factor (GDNF) mRNA expression via the transactivation of fibroblast growth factor receptor 2 (FGFR2) in rat C6 glioma cells. 1836 29

The present study was undertaken to determine the molecular mechanism by which kaempferol induces cell death in human glioma cells. Kaempferol resulted in loss of cell viability and inhibition of proliferation in a dose- and time-dependent manner, which were largely attributed to cell death. Kaempferol caused an increase in reactive oxygen species (ROS) generation and the kaempferol-induced cell death was prevented by antioxidants, suggesting that ROS generation is involved in kaempferol-induced cell death. Kaempferol caused depolarization of mitochondrial membrane potential. Western blot analysis showed that kaempferol treatment caused a rapid reduction in phosphorylation of extracellular signal-regulated kinase (ERK) and Akt. The ERK inhibitor U0126 and the Akt inhibitor LY984002 increased the kaempferol-induced cell death and overexpression of MEK, the upstream kinase of ERK, and Akt prevented the cell death. The expression of anti-apoptotic proteins XIAP and survivin was down-regulated by kaempferol and its effect was prevented by overexpression of MEK and Akt. Kaempferol induced activation of caspase-3 and kaempferol-induced cell death was prevented by caspase inhibitors. Taken together, these findings suggest that kaempferol results in human glioma cell death through caspase-dependent mechanisms involving down-regulation of XIAP and survivin regulating by ERK and Akt.
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PMID:Kaempferol induces cell death through ERK and Akt-dependent down-regulation of XIAP and survivin in human glioma cells. 1894 56

RAF proteins are well known oncoproteins. The B-RAF has been shown to be activated by mutations in a multitude of human cancers. Alterations of C-RAF expression are discussed to play a role in lung cancer. Only for A-RAF no link to tumorigenesis has been published so far. Malignant gliomas are the most prevalent primary brain tumors of adults. They are highly invasive and very difficult to treat, despite of surgery, gamma-irradiation and chemotherapy. Although a role of the mitogenic Ras-RAF-MEK-ERK signalling cascade in brain tumor development is well established, there are only few reports available addressing alterations in RAF sequence or protein expression and function in human gliomas. We analysed the mutational status of A-RAF and B-RAF in human glioblastomas (GBM) by sequencing. Then we checked for RAF gene amplification by dot blot hybridization and examined RAF mRNA and protein expression patterns in human astrocytic gliomas of WHO grade II (LGA) and IV (GBM) by semiquantitative RT-PCR and Western blotting, respectively. The results were correlated with patients prognosis. Finally, we performed functional assays to address a putative function of A-RAF in glioma cell proliferation and migration. We showed that RAF mutations are a rare event in glioblastoma multiforme. A-raf gene amplification was more often detected and overexpression of all three RAF proteins on mRNA and protein level was regularly found in human malignant gliomas. Whereas A-RAF and C-RAF expression was negatively correlated with the patients prognosis, B-RAF expression had a positive effect. Since neither A-RAF, nor C-RAF expression had any influence on proliferation and migration of GBM cells, putative functions of C-RAF in angiogenesis and of A-RAF in regulation of metabolism are discussed. Our data indicate that RAF proteins might be valuable targets for small molecule therapies. However, initially specific functions of RAF during tumorigenesis have to be elucidated.
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PMID:RAF expression in human astrocytic tumors. 1908 3

Ion channels are found in a variety of cancer cells and necessary for cell cycle and cell proliferation. The roles of K(+) channels in the process are, however, poorly understood. In the present study, we report that adenosine triphosphate (ATP)-sensitive potassium channel activity plays a critical role in the proliferation of glioma cells. The expression of K(ATP) channels in glioma tissues was greatly increased than that in normal tissues. Treatment of glioma cells with tolbutamide, K(ATP) channels inhibitor, suppressed the proliferation of glioma cells and blocked glioma cell cycle in G(0)/G(1) phase. Similarly, downregulation of K(ATP) channels by small interfering RNA (siRNA) inhibited glioma cell proliferation. On the other hand, K(ATP) channels agonist diazoxide and overexpression of K(ATP) channels promoted the proliferation of glioma cells. Moreover, inhibiting K(ATP) channels slowed the formation of tumor in nude mice generated by injection of glioma cells. Whereas activating K(ATP) channels promoted development of tumor in vivo. The effect of K(ATP) channels activity on glioma cells proliferation is mediated by extracellular signal-regulated kinase (ERK) activation. We found that activating K(ATP) channel triggered ERK activation and inhibiting K(ATP) channel depressed ERK activation. U-0126, the mitogen-activated protein kinase kinase (MAPK kinase) inhibitors blocked ERK activation and cell proliferation induced by diazoxide. Furthermore, constitutively activated MEK plasmids transfection reversed the inhibitory effects of tolbutamide on glioma proliferation, lending further support for a role of ERK in mediating this process. Our results suggest that K(ATP) channels control glioma cell proliferation via regulating ERK pathway. We concluded that K(ATP) channels are important in pathological cell proliferation and open a promising pathway for novel targeted therapies.
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PMID:ATP-sensitive potassium channels control glioma cells proliferation by regulating ERK activity. 1917 41

Prostaglandin-F(2alpha) (PGF(2alpha)) is a product of the cyclooxygenase pathway and is a local signaling molecule that activates a G-protein coupled prostanoid receptor named FP. FP receptors can stimulate T-cell factor (Tcf) transcriptional activation by stabilization of beta-catenin and can upregulate the expression of mRNA encoding cysteine-rich protein 61 (Cyr61), a secreted extracellular matrix protein that stimulates angiogenesis. We now show in both HEK cells and human microglial cells that the induction of Cyr61 protein expression by the human FP receptor utilizes a novel mechanism involving the activation of Ras and Raf followed by a MEK/ERK independent activation of Tcf signaling. The upregulation of Cyr61 in microglial cells may contribute to glioma tumorigenesis and could be a potential therapeutic target.
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PMID:PGF(2alpha) stimulates FP prostanoid receptor mediated crosstalk between Ras/Raf signaling and Tcf transcriptional activation. 1924 65


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