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 use of bisindolylmaleimide derivatives of staurosporine as selective inhibitors of protein kinase C (PKC) is in doubt following the report by Alessi [FEBS Lett. 402 (1997) 121-123] that Ro31-8220 and GF109203X are potent in vitro inhibitors of p70 S6 kinase and mitogen-activated protein kinase-activated protein kinase-1beta, as well as of PKC. Here we show that the phorbol ester-stimulated release of choline- and ethanolamine-metabolites from C6 glioma cells due to phospholipid hydrolysis by phospholipase D (PLD) is not inhibited by rapamycin or PD98059, specific inhibitors respectively of p70 S6 kinase and MAPKK (MEK) and thus of MAPKAP kinase-1beta but is still completely blocked by Ro31-8220. We conclude therefore that p70S6k and MAPKAP kinase-1beta as well as MAPK are not involved in signalling pathways downstream of PKC that regulate phorbol ester-stimulated phospholipid turnover and that the inhibitory action of Ro31-8220 occurs by blocking PKC which regulates at least one pathway to PLD activation. The PI-3 kinase inhibitor, wortmannin, inhibits the phorbol ester-stimulated release of ethanolamine- but not choline-metabolites from C6 cells suggesting that different PLD isoforms regulate the turnover of PtdEth and PtdCho in C6 cells. Both PLD isoforms are activated via PKC but the PtdEth-PLD is also regulated via a wortmannin-sensitive pathway.
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PMID:Ro31-8220 inhibits protein kinase C to block the phorbol ester-stimulated release of choline- and ethanolamine-metabolites from C6 glioma cells: p70 S6 kinase and MAPKAP kinase-1beta do not function downstream of PKC in activating PLD. 939 70

The effect of stress on the production of cytokine-induced neutrophil chemoattractant (CINC) was examined in rat C6 glioma cells. We studied the production of CINC, an interleukin-8 (IL-8) family protein, with bacterial endotoxin, H2O2, and tumor necrosis factor-alpha (TNF-alpha). Each stress induced CINC mRNA in a concentration-dependent manner. Since stress activates the protein kinases regulating nuclear transcription factors, we examined the effects of protein kinase inhibitors and the over-expression of dominant-negative Ras on CINC mRNA expression. Neither over-expression of dominant-negative Ras nor pretreatment with PD98059 (MEK-1 inhibitor), SB203580 (p38MAPK inhibitor), or GF109203X (protein kinase C (PKC) inhibitor) altered stress-induced CINC mRNA expression. This suggests that the Ras-MAPK, p38MAPK, and PKC pathways are not involved in CINC mRNA expression in glial cells. On the other hand, pretreatment with herbimycin A, a potent tyrosine kinase inhibitor, or Ro31-8220, a non-selective serine/threonine kinase inhibitor, suppressed stress-induced CINC mRNA expression. This indicates that stress-induced CINC mRNA expression is mediated by herbimycin A-, or Ro31-8220-sensitive kinases in glial cells. Since stress activates NF-kappaB and NF-IL6, we examined that the effect of herbimycin A, which suppresses CINC mRNA expression, on NF-kappaB and NF-IL6 activation. Herbimycin A suppressed NF-kappaB but not NF-IL6. These results suggest that in rat glial cells, the factors that induce CINC mRNA expression are mediated by herbimycin A-sensitive NF-kappaB activation, but not through the PKC, Ras-MAPK or p38 MAPK pathways.
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PMID:Induction of cytokine-induced neutrophil chemoattractant in response to various stresses in rat C6 glioma cells. 959 44

Mitogen-activated protein kinase (MAPK) is a family of serine/threonine kinase that appears to be a component common to signalling pathway initiated by a wide range of factors including hormones, differentiation factors and mitogens. Baicalein is a flavonoid derived from the root of Scutellaria baicaleins. From searching the inhibitors of prostaglandin synthesis in C6 rat glioma cells, we found that baicalein had a potent inhibitory activity of prostaglandin synthesis induced by either histamine or A23187, a Ca2+ ionophore. Baicalein inhibited histamine- and A23187-induced phosphorylation of MAPK in the cells, which was known to cause the phosphorylation of cytosolic phospholipase A2. Baicalein also inhibited the phosphorylation of MAPK kinase (MEK) induced by histamine or A23187 in the cells. In vitro kinase assay, baicalein inhibited the activities of raf but not MEK. These results imply that baicalein is a specific inhibitor of MAPK cascade, acting on phosphorylation of MEK by raf.
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PMID:[Inhibition of mitogen-activated protein kinase cascade by baicalein, a flavonoid of natural origin]. 1062 83

1. Extracellular purine and pyrimidine nucleotides have been implicated in the regulation of several cellular functions including mitogenesis. In this study, experiments were conducted to characterize the P2Y receptor on C(6) glioma cells responsible for stimulating cell proliferation associated with mitogen-activated protein kinase (MAPK) activation. 2. UTP and ATP produced a similar effect on [(3)H]-thymidine incorporation in a time- and concentration-dependent manner, suggesting the involvement of P2Y(2) receptor in mediating proliferation of C(6) glioma cells. 3. In response to UTP, both p42 and p44 MAPK were activated in a time- and concentration-dependent manner using Western blot analysis with an anti-phospho-p42/p44 MAPK antibody. The phosphorylation reached maximal levels after 5 min and declining by 30 min. 4. Pretreatment with pertussis toxin (PTX) did not change these responses to UTP. Both DNA synthesis and phosphorylation of MAPK in response to UTP were attenuated by tyrosine kinase inhibitors, genistein and herbimycin A, protein kinase C (PKC) inhibitors, staurosporine and GF109203X, and removal of Ca(2+) by addition of BAPTA/AM plus EGTA. 5. UTP-induced [(3)H]-thymidine incorporation and p42/p44 MAPK phosphorylation was completely inhibited by PD98059 (an inhibitor of MEK1/2). Furthermore, we showed that overexpression of dominant negative mutants of Ras (RasN17) and Raf (Raf-301) completely suppressed MEK1/2 and p42/p44 MAPK activation induced by ATP and UTP. 6. These results conclude that the mitogenic effect of UTP mediated through a P2Y(2) receptor that involves the activation of Ras/Raf/MEK/MAPK pathway. UTP-mediated MAPK activation was modulated by Ca(2+), PKC, and tyrosine kinase associated with cell proliferation in cultured C(6) glioma cells.
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PMID:P2Y(2) receptor-mediated proliferation of C(6) glioma cells via activation of Ras/Raf/MEK/MAPK pathway. 1074 5

Recent studies have revealed that a variety of malignant tumors express Fas and/or its ligand FasL. However, tumor cells expressing Fas are not always susceptible to Fas-mediated cell death, and the biological significance of simultaneous expression of Fas and FasL in the same tumor is not known. In the present study, we addressed this question in three glioma cells lines, A-172, T98G, and YKG-1, which express both Fas and FasL endogenously and their Fas transfectants. We report here that: (a) in gliomas, [3H]TdR incorporation was enhanced by anti-Fas IgM monoclonal antibody CH-11 and conversely inhibited by anti-FasL monoclonal antibody NOK-2; (b) cross-linking of Fas with CH-11 drove both cell cycle progression and apoptosis as demonstrated by the induction of the S-G2 phase of DNA and RNA and fragmented nuclei; (c) phosphorylation of extracellular signal-regulated kinase (ERK), but not of c-Jun NH2-terminal kinase or p38, was induced by cross-linking of Fas; (d) a mitogen-activated protein kinase/ERK kinase 1 (MEK1) inhibitor PD98059 completely blocked CH-11-induced ERK phosphorylation as well as cell cycle progression without affecting induction of apoptosis; and (e) a broad-spectrum caspase inhibitor Z-Asp-CH2-DCB inhibited CH-11-induced ERK phosphorylation, cell cycle progression, and apoptosis. These results indicate that Fas-mediated caspase activation elicits two independent cellular responses; one is to induce apoptosis and another is to promote cell cycle progression; the latter is closely linked to the MEK-ERK pathway. Together, our data strongly suggest that FasL may play a role as an autocrine growth factor in gliomas.
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PMID:Fas drives cell cycle progression in glioma cells via extracellular signal-regulated kinase activation. 1074 52

Normal human fibroblasts have been shown to undergo a p16(Ink4a)-associated senescence-like growth arrest in response to sustained activation of the Ras/Raf/MEK/ERK pathway. We noted a similar p16(Ink4a)-associated, senescence-like arrest in normal human astrocytes in response to expression of a conditional form of Raf-1. While HPV16 E7-mediated functional inactivation of the p16(Ink4a)/pRb pathway in astrocytes blocked the p16(Ink4a)-associated growth arrest in response to activation of Raf-1, it also revealed a second p21(Cip1)-associated, senescence-associated, beta-galactosidase-independent growth arrest pathway. Importantly, the p21(Cip1)-associated pathway was present not only in normal astrocytes but also in p53-, p14(ARF)-, and p16(Ink4a)/pRb-deficient high grade glioma cells that lacked the p16(Ink4a)-dependent arrest mechanism. These results suggest that normal human cells have redundant arrest pathways, which can be activated by Raf-1, and that even tumors that have dismantled p16(Ink4a)-dependent growth arrest pathways are potentially regulated by a second p21(Cip1)-dependent growth arrest pathway.
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PMID:Dual growth arrest pathways in astrocytes and astrocytic tumors in response to Raf-1 activation. 1127 20

We have previously shown that an ecto-NPPase modulates the ATP- and ADP-mediated P2Y(AC)-receptor activation in rat C6 glioma. In the present study, 2MeSADP and Ap(3)A induced no detectable PI turnover and were identified as specific agonists of the P2Y(AC)-receptor with EC(50) values of 250 +/- 37 pM and 1 +/- 0.5 microM, respectively. P2Y(AC)-receptor stimulation increased MAP kinase (ERK1/2) activation that returned to the basal level 4 h after stimulation and was correlated with a gradual desensitization of the P2Y(AC)-purinoceptor. The purinoceptor antagonists DIDS and RB2 blocked MAP kinase activation. An IP(3)-independent Ca(2+)-influx was observed after P2Y(AC)-receptor activation. Inhibition of this influx by Ca(2+)-chelation, did not affect MAP kinase activation. Pertussis toxin, toxin B, selective PKC-inhibitors and a specific MEK-inhibitor inhibited the 2MeSADP- and Ap(3)A-induced MAP kinase activation. In addition, transfection with dominant negative RhoA(Asn19) rendered C6 cells insensitive to P2Y(AC)-receptor-mediated MAP kinase activation whereas dominant negative ras was without effect. Immunoprecipitation experiments indicated a significant increase in the phosphorylation of raf-1 after P2Y(AC)-receptor activation. We may conclude that P2Y(AC)-purinoceptor agonists activate MAP kinase through a G(i)-RhoA-PKC-raf-MEK-dependent, but ras- and Ca(2+)-independent cascade.
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PMID:Agonists of the P2Y(AC)-receptor activate MAP kinase by a ras-independent pathway in rat C6 glioma. 1157 41

Hepatocyte growth factor (HGF) and its receptor c-Met are expressed in inappropriately high abundance in gliomas and are further upregulated during the transition from low- to high-grade malignancy. In these cells HGF induces expression of c-Met via PKC, Ras and mitogen activated protein kinase (MAPK) pathway. Here we report that secretion and expression of HGF in U87 astrocytoma is increased by a PKC activator, PMA, an effect which is abolished by a PKC inhibitor, Go6976, specific for PKCalpha and PKCbeta1. Activating PKA by forskolin, on the other hand, had no effect. Furthermore, messenger molecule downstream of PKC, i.e. MEK mediates such effect of PKC as specific MEK inhibitors (PD98059 and U0126) abolished PMA induced HGF secretion by U87 cells. Accordingly, PMA induced rapid phosphorylation of MEK substrate, i.e. Erk1/2 (p42/44 MAPK). In addition, such effect of PKC is Ras-dependent as specific Ras inhibitor L-744,832 attenuated both PMA mediated induction of Erk 1/2 phosphorylation as well as HGF secretion. Moreover, a specific p38 MAPK inhibitor (SB203580) almost completely inhibited basal HGF secretion to an undetectable level. Increased secretion of HGF is most likely exerted at the transcriptional level since inhibitor of transcription, actinomycin D abolished such increase. Furthermore, when assessed by Northern blot analysis, PMA increased HGF transcripts while U0127 and SB203580 inhibited. Therefore, our data reveal that HGF secretion in U87 cells is regulated by Ras-dependent PKC, MEK cascade and in parallel by p38 MAPK pathway. Since the Raf-PKC-MEK cascade is used for HGF's signaling via its receptor in astrocytoma cells, our data revealing similar regulatory mechanism for HGF secretion in these cells would help to explain the feed forward nature of HGF action in glioma cells that would further accentuate its basal secretion, exacerbating its effects on the progression of gliomas in an autocrine fashion.
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PMID:PKC, p42/44 MAPK and p38 MAPK regulate hepatocyte growth factor secretion from human astrocytoma cells. 1219 96

To investigate regulation of D2 receptor (D2R) gene expression by protein kinases, we evaluated effects of constitutively active MAPK kinase kinase (MEKK), Ca2+/calmodulin-dependent protein kinase (CaMK) II, CaMKIV and cyclic AMP-dependent protein kinase (PKA) on D2R promoter activity using luciferase reporter gene assays. A 1.5-kbp fragment containing the rat D2R promoter was cloned upstream of the reporter and transfected into D2R-expressing NB2A cells or nonexpressing NG108-15 and C6 glioma cells. MEKK and CaMKII, but not CaMKIV and PKA, increased promoter activity 4.5- and 1.5-fold, respectively, in NB2A cells. Inhibitory effects of a MEK inhibitor and lack of effect by dominant negative (DN)-JNK1 or DN-p38MAPK revealed that ERK but not JNK and p38MAPK is involved in MEKK-induced promoter activation. Deletion and mutation of the promoter revealed that the MEKK-responsive region was Sp1 site B between nucleotides -56 and -47. Overexpression of Sp1 suppressed promoter activity without affecting MEKK-induced activation. Interestingly, overexpression of Zif268 increased promoter activity through the region between nucleotides -56 and -36. Increased activity by Zif268 was additive with CaMKII-induced activation but not with activation induced by MEKK. Co-transfection with CaMKII stimulated nuclear translocation of Zif268. These results suggest that ERK and CaMKII positively regulate the D2R promoter and that Zif268 is a potential transcription factor for the CaMKII-dependent pathway.
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PMID:Activation of the rat dopamine D2 receptor promoter by mitogen-activated protein kinase and Ca2+/calmodulin-dependent protein kinase II pathways. 1242 50

Baicalein is a flavonoid derived from the Scutellaria root. In investigations of the inhibitors of prostaglandin synthesis in C6 rat glioma cells, we found that baicalein had a potent inhibitory activity on prostaglandin synthesis induced by either histamine or A23187, a Ca(2+) ionophore. Baicalein inhibited histamine- or A23187-induced phosphorylation of p42/p44 extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK), which causes the phosphorylation of cytosolic phospholipase A(2) (PLA(2)). Baicalein also inhibited the phosphorylation of MAPK kinase-1 (MEK-1) induced by histamine or A23187 in the cells. To examine the site of action of baicalein, MEK-1 and Raf-1 were prepared by immunoprecipitation with anti-MEK-1 and anti-Raf-1 antibodies, respectively. Baicalein inhibited the phosphorylation of exogenous MEK-1 by Raf-1 under cell-free conditions, while it did not change the phosphorylation of exogenous p42 MAPK by MEK-1. These results imply that baicalein inhibits the ERK/MAPK cascade, acting on the phosphorylation of MEK-1 by Raf-1.
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PMID:Baicalein inhibits Raf-1-mediated phosphorylation of MEK-1 in C6 rat glioma cells. 1256 9


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