Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The genetic abnormality most frequently identified in glioblastomas is loss of alleles on chromosome 10. We have performed a comprehensive study of the PTEN tumor suppressor gene on 10q23, including loss of heterozygosity (LOH) analysis, multiplex PCR, mutation analysis, and reverse transcription PCR (RT-PCR). In total, 151 glioblastomas, 41 anaplastic astrocytomas, 15 astrocytomas, and 13 glioma cell lines were analyzed as well as 23 xenografts derived from primary glioblastomas, which allows a comparison of the PTEN gene status in primary tumors versus xenografts. Homozygous deletions were found in 7% of the glioblastomas and 40% showed mutation of a single retained allele. This mutation frequency is higher than reported previously. The large number of mutations identified allows the presentation of a mutational profile along the coding sequence. The majority of mutations appear to affect conserved residues or structurally conserved regions. PTEN alterations were selected for in xenografts, and there is evidence that they may even facilitate establishment of xenografts. No alterations were found in astrocytomas and only 5% of anaplastic astrocytomas had mutations. Thus, loss of wild type PTEN represents one of the major abnormalities associated with astrocytic tumor progression to glioblastoma and provides a strong selective growth advantage when cultivating glioblastoma tissue in xenografts. No correlation with EGFR amplification was evident.
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PMID:Mutational profile of the PTEN gene in primary human astrocytic tumors and cultivated xenografts. 1056 Jun 60

Scatter factor/hepatocyte growth factor (SF/HGF) is a pleiotrophic cytokine that stimulates motility and invasion of several cancer cell types and induces angiogenesis. Its receptor MET is a transmembrane tyrosine kinase encoded by the C-MET proto-oncogene. To assess the potential relevance of SF/HGF in gliomas we performed functional studies in vivo and in vitro, expression analyses and correlative studies. We showed that both SF/HGF and MET are expressed in gliomas in vivo and are upregulated during transition from low grade to malignant glioma. When SF/HGF cDNA was transfected into glioma cells that expressed the MET receptor the cells formed considerably larger and more vascularized intracranial tumors in vivo than SF/HGF negative control clones. In other glioma cells, which constitutively expressed both SF/HGF and MET, we abolished SF/HGF expression by antisense ribozyme-targeting, which led to a significant decrease in tumorigenicity and tumor growth. In vitro SF/HGF strongly stimulated glioma cell motility and to a lesser degree proliferation. SF/HGF also strongly increased endothelial cell motility in vitro and extracts of tumors derived from SF/HGF-transfected glioma cells were more mitogenic for endothelial cells and more angiogenic in the rat cornea angiogenesis assay than extracts from control tumors. In a three-dimensional in vitro angiogenesis assay basic fibroblast growth factor (bFGF) was found to synergize with either SF/HGF or vascular endothelial growth factor (VEGF) in inducing endothelial capillary-like tubes, whereas neither SF/HGF nor VEGF alone or in combination were effective. Interestingly, while both VEGF and SF/HGF levels appeared to be increased in malignant gliomas compared with low grade ones, this was not the case for bFGF of which biologically relevant levels were already present in low grade gliomas. It thus seems that bFGF alone is insufficient to induce angiogenesis in gliomas but may act synergistically with either VEGF and/or SF/HGF when these become upregulated during malignant progression. In conclusion, we showed that SF/HGF may contribute to glioma progression by stimulating tumor invasiveness, proliferation and neovascularization.
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PMID:Scatter factor/hepatocyte growth factor (SF/HGF) content and function in human gliomas. 1057 13

Vascular endothelial growth factor (VEGF) is one of the key factors in tumor neoangiogenesis, acting through its receptors KDR (VEGFR-2) and fit-1 (VEGFR-1) expressed on endothelial cells. Our data demonstrate that VEGFR-1 and to a lesser extent VEGFR-2 are expressed in a number of human tumor tissues and derived cells in culture. VEGFR-1 protein is expressed in 26 of 42 glioma tissues, 22 of which show a coexpression of VEGFR-1 with VEGFR-2; 1 glioma tissue expresses exclusively VEGFR-2. In the derived glioma cell cultures, we found VEGFR-1 mRNA expression in 6 of 11 cultures, with one coexpressing VEGFR-1 and VEGFR-2. Of four established glioma cell lines, two expressed VEGFR-1. In addition VEGFR-1 protein expression was demonstrated in 30 of 37 tumor tissues of squamous cell carcinomas of the head and neck, with VEGFR-2 coexpression in 15 tissues and an expression of VEGFR-2 alone in 1 tissue. Derived tumor cell cultures showed mRNA expression of VEGFR-1 alone in seven of seven cases. Established melanoma cell lines expressed VEGFR-1 mRNA in four of five lines, with VEGFR-2 coexpression in two lines. Concerning the functional significance of VEGF receptor expression, VEGF treatment of VEGFR-1-expressing tumor cells induced the inhibition of cell proliferation by 25 to 55% and the inhibition of tumor cell migration by 29 to 55%. Thus our data indicate that the coexpression of VEGF and VEGFR-1 in tumor cells could have an inhibitory effect on tumor cell proliferation and migration, a mechanism possibly induced as a response to a deficiency in nutrient and oxygen supply.
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PMID:Expression and functional significance of vascular endothelial growth factor receptors in human tumor cells. 1061 7

Basic fibroblast growth factor (FGF-2) and high affinity FGF receptor (FGFR) have been detected in the nucleus as well as the cytoplasm of many human gliomas, and are known to stimulate cellular proliferation and angiogenesis in the tumors. To investigate the effects of inactivation of FGFR on the growth of malignant gliomas, we constructed a replication-deficient recombinant adenovirus vector encoding a truncated form of chicken FGFR1 (AxCA delta FR). AxCA delta FR-infected cells were confirmed to express truncated FGFR protein by immunoblotting and FGF-2-dependent clonogenicity of NIH3T3 cells was suppressed by infection with this virus vector. Then human malignant glioma cell lines U-251MG and T98G, both of which have been reported to express FGF-2 and FGFR, were infected with AxCA delta FR. These infected cells showed nuclear as well as cytoplasmic expression of a truncated FGFR protein. Proliferation rate and the ability to form colonies in soft agar of the cells infected with this virus vector were significantly suppressed compared with those of uninfected and lacZ-expressing adenovirus-infected cells. Moreover, intratumoral injection of AxCA delta FR significantly suppressed the subcutaneous tumor growth of the glioma cells in nude mice. We concluded that inactivation of the cytoplasmic and nuclear FGFR using this truncated FGFR-expressing adenovirus vector can inhibit the growth of malignant gliomas both in vitro and in vivo.
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PMID:Adenovirus-mediated gene transfer of a truncated form of fibroblast growth factor receptor inhibits growth of glioma cells both in vitro and in vivo. 1072 Jan 99

Permanent glioma cell lines are invaluable tools in understanding the biology of glioblastomas. The present study reports the establishment of a clonal human cell line, GBM6840, derived from a biopsy of paediatric cerebellar glioblastoma multiforme. GBM6840 had a doubling time of 32 h and grew as a monolayer of large round cells that retained immunopositivity for glial fibrillary acidic protein and vimentin. Karyotypic analysis revealed a modal chromosome number of 68 and polysomies of chromosomes 3, 5 and 20, as well as the presence of 3-4 marker chromosomes. GBM6840 also showed anchorage-independent growth in soft agar and tumour formation in nude mice. The p16(CDKN2A) gene was transcriptionally silenced by hypermethylation, consistent with the lack of protein expression observed in the original tumour and cultured cells. Western blot analysis revealed normal protein expression of pRb and CDK4. It appears that p16 is the major component altered in the cell cycle pathway and may confer these cells unrestrained proliferation potential. Neither EGFR gene amplification nor over-expression of the protein was detected in the cultured cells. Over-expression of the p53 protein was observed in the majority of cells, despite undetectable mutation (exons 5-8) in the gene. One allele of the PTEN gene was found to be mutated during in vitro cultivation. Telomerase activity was demonstrated in the cultured cells but not in the original tumour, supporting the hypothesis that telomerase is required for the in vitro immortalization process.
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PMID:Establishment and characterization of a human cell line from paediatric cerebellar glioblastoma multiforme. 1073 64

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

The role of nitric oxide (NO) and adherent spleen cells in systemic immunosuppression developing in animals carrying malignant glioma isografts was analyzed. Rats harboring a subcutaneous glioma isograft for 3 weeks were immunized with glioma cells genetically engineered to express IFN-gamma. One week later spleen cells were tested for immune responsiveness in vitro. A decreased cytotoxic activity of NK-cells and T-cells compared to tumor-free animals immunized in parallel was shown. Spleen cell proliferative responses to tumor cells, SEA, and anti-CD3 were all significantly suppressed, as was the production of IFN-gamma and IL-10. Plastic adherent spleen cells from tumor-bearing rats suppressed the SEA-induced proliferative response and the production of IFN-gamma and IL-10 by nonadherent spleen cells from tumor-free rats. A major part of this suppression appears to be dependent on the production of NO because suppression was efficiently counteracted in vitro by the NO-synthase inhibitor N-nitro-l-arginine methyl ester. Moreover, a significantly increased level of nitrite in culture supernatants correlated with the observed suppression. We conclude that the systemic immunosuppression associated with growing gliomas is in part mediated by mechanisms dependent on NO overproduction in adherent spleen cells.
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PMID:Nitric-oxide-dependent systemic immunosuppression in animals with progressively growing malignant gliomas. 1075 3

The effect of lipopolysaccharide (LPS) on the expression of immediate early genes, such as c-fos and c-jun, was examined in C6 rat glioma cells. LPS (1 microg/ml) alone did not affect c-fos mRNA level. LPS, however, transiently increased c-jun mRNA level. Cycloheximide (CHX, 20 microM), a protein synthesis inhibitor, alone caused increases of c-fos and c-jun mRNA levels. LPS showed a potentiating effect in the regulation of c-fos mRNA level, whereas LPS showed an additive action for the regulation of CHX-induced c-jun mRNA expression. To determine if CREB and mitogen-activated protein kinases (MAPKs) are involved in the regulation of c-fos mRNA expression by LPS and CHX, Western blot was carried out using the phosphorylated form of antibodies against ERK, JNK, p38, and CREB. LPS transiently increased the phosphorylation of p38-MAPK and CREB. In addition, LPS alone elevated phosphorylation of ERK (p44/p42) MAPK in a time-dependent manner. Furthermore, LPS plus CHX enhanced phosphorylation of ERK, p38, and CREB in a synergistic manner. Our results suggest that the phosphorylation of ERK, p38, and CREB may be involved in the regulation of synergistic c-fos mRNA expression induced by LPS plus CHX in C6 rat glioma cells.
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PMID:Regulation of c-fos gene expression by lipopolysaccharide and cycloheximide in C6 rat glioma cells. 1092 99

Vascular endothelial growth factor, fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) and their cognate receptor tyrosine kinases are strongly implicated in angiogenesis associated with solid tumors. Using rational drug design coupled with traditional screening technologies, we have discovered SU6668, a novel inhibitor of these receptors. Biochemical kinetic studies using isolated Flk-1, FGF receptor 1, and PDGF receptor beta kinases revealed that SU6668 has competitive inhibitory properties with respect to ATP. Cocrystallographic studies of SU6668 in the catalytic domain of FGF receptor 1 substantiated the adenine mimetic properties of its oxindole core. Molecular modeling of SU6668 in the ATP binding pockets of the FIk-1/KDR and PDGF receptor kinases provided insight to explain the relative potency and selectivity of SU6668 for these receptors. In cellular systems, SU6668 inhibited receptor tyrosine phosphorylation and mitogenesis after stimulation of cells by appropriate ligands. Oral or i.p. administration of SU6668 in athymic mice resulted in significant growth inhibition of a diverse panel of human tumor xenografts of glioma, melanoma, lung, colon, ovarian, and epidermoid origin. Furthermore, intravital multifluorescence videomicroscopy of C6 glioma xenografts in the dorsal skinfold chamber model revealed that SU6668 treatment suppressed tumor angiogenesis. Finally, SU6668 treatment induced striking regression of large established human tumor xenografts. Investigations of SU6668 activity in cancer patients are ongoing in Phase I clinical trials.
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PMID:SU6668 is a potent antiangiogenic and antitumor agent that induces regression of established tumors. 1094 23

Multiple mechanisms, such as gene mutations, amplifications, and rearrangements, as well as perturbed mitogen and receptor function, are likely to contribute to glioma formation. The MET (also known as c-met proto-oncogene located at 7q31-34 has been shown to be amplified in human gliomas, and activating mutations within the tyrosine kinase domain of MET have been causally related to tumorigenesis in hereditary papillary renal cell carcinoma. To elucidate the role of MET gene in glioma formation, sporadic gliomas from 11 patients were examined for MET gene mutations and allelic duplications or deletions by polymerase chain reaction-single strand conformational polymorphism analysis and fluorescence in situ hybridization. Three of 11 sporadic gliomas showed a deletion of one copy of the MET gene, and a specific METgene missense mutation in the remaining gene copy was detected in one of those tumors. The corresponding sequence in non-tumor DNA was normal in all cases. Three of 11 sporadic gliomas showed duplication of one copy of the MET gene, but none of them contained mutations. One tumor showed METamplification without mutation. Three showed neither allelic change nor mutation. These data suggest that somatic MET gene mutation may play a role in the development of a subgroup of sporadic gliomas. However, MET mutations appear to be absent in the majority of sporadic gliomas.
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PMID:Missense mutation of the MET gene detected in human glioma. 1100 37


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