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 cell-surface urokinase plasminogen activator receptor (uPAR) plays a key role in regulating plasminogen cleavage during extracellular proteolysis. Our recent results demonstrated that uPAR expression is critical for the invasiveness of human gliomas and down regulation of uPAR caused by antisense cDNA transfection inhibits the invasion of these stable antisense uPAR-transfectant clones. To study the role of uPARs in glioma cell invasion, a human neuroglioma cell line (H4) that normally produces low numbers of uPARs was transfected with the expression vector containing full-length human uPAR cDNA. Stable transfectants were analyzed for uPAR mRNA expression, receptor number, in vitro invasion and secretion of uPA and MMP-2. The uPAR-overproducing clones showed a 4-fold increase in uPAR mRNA transcription and approximately 40% increase in receptor numbers. uPAR-overproducing clones also invaded through matrigel to a significantly greater extent than did parent cell line and vector clones. However, the uPAR-overexpressing clones and parent cell lines showed similar uPA and MMP-2 activities. These results suggest that the over-production of uPAR on the surface of neuroglioma cells enhances the invasiveness.
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PMID:Increased invasion of neuroglioma cells transfected with urokinase plasminogen activator receptor cDNA. 982 46

Human malignant gliomas are highly vascularized and aggressive tumors. Angiogenesis inhibitors have been shown to induce regression of a variety of primary and metastatic tumors in vivo. However, their usefulness in treating brain tumors is not well understood. Angiostatin, a multiple kringle (1-4 of 5)-containing fragment of plasminogen, is one of the highly effective natural cryptic angiogenesis inhibitors. In our study, the therapeutic efficacy of non-glycosylated and small molecular size recombinant kringles 1-3 (rPK1-3) was examined in the treatment of brain tumors generated by stereotactic intracerebral implantation of U-87 human glioma cells in nude mice. Mice bearing tumors 7 days post-implant were treated daily with rPK1-3 (100 mg/kg) s.c. for 21 days. Treated animals showed suppressed brain tumor growth by greater than 71.2% along with a 3-fold increase of apoptotic index and suppressed vascularization by 78.9%, without any observable signs of toxicity. Analysis of bFGF and VEGF expression in the tumors of treated animals using immuno-histochemical methods showed near complete absence of growth factors. Our results indicate that the non-glycosylated, small molecular size rPK1-3 is an efficient tumoristatic agent for the treatment of intracranial human glioma xenografts in mice and might provide new strategies for the treatment of brain tumors.
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PMID:Inhibition of human malignant glioma growth in vivo by human recombinant plasminogen kringles 1-3. 1041 67

Various proteases and their inhibitors have been shown to be important in tumor invasion. Angiogenesis is further a prerequisite for the growth and progression of solid tumors. Since these systems are functionally linked, in situ hybridization and in situ zymography were used to investigate the spatial and temporal expression of factors representative of the plasmin/plasminogen system and of an angiogenic factor in the BT4C glioma model. This tumor is invasive with a high grade of neovascularization. Tissue-type plasminogen activator urokinase-type plasminogen activator and plasminogen activator inhibitor-1 mRNA were expressed in glioma cells during the entire tumor growth. Early in the tumor development the expression was found throughout the small tumor (approximately 10 mm3) while later in the time course the expression was found predominantly in the invasive tumor border of the tumor. The in situ zymography demonstrated that the plasminogen activators were translated into functional proteins. Vascular endothelial growth factor mRNA was expressed following a similar spatial and temporal pattern with an early expression in the entire small tumor while later, in larger tumors, it was exclusively expressed in the invasive tumor edge. In normal brain, the ventricular ependyma, meninges, as well as scattered neurons expressed tissue-type plasminogen activator mRNA. Vascular endothelial growth factor mRNA was observed in the choroid plexus, and in scattered cells in normal brain tissue. Our finding may suggest a functional co-operation of tissue-type plasminogen activator, urokinase-type plasminogen activator, plasminogen activator inhibitor-1 and vascular endothelial growth factor during glioma progression. This model could be of value when evaluating different treatment modalities aimed at blocking the migrating capacity and growth of glial tumors.
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PMID:Expression of the proteolytic factors, tPA and uPA, PAI-1 and VEGF during malignant glioma progression. 1057 9

Angiostatin is an endogenous inhibitor of tumor neovascularization that inhibits the proliferation of endothelial cells. Production of sufficient quantities of biologically active angiostatin by the enzymatic cleavage of plasminogen has proven difficult in that it has delayed clinical testing. We have cloned, expressed, and purified a recombinant human angiostatin derivative (K1-3) using a mammalian expression system. Through the addition of a secretory signal and polyhistidine sequence tag, K1-3 can be purified from post-culture medium by simple column chromatography. Purified K1-3 protein is apparently folded in an active conformation, as evidenced by its ability to bind to lysine-Sepharose. In vitro, recombinant K1-3 significantly suppressed endothelial cell proliferation in a dose-dependent manner with an IC50 of 50 nM. Using an animal model of intracranial brain tumors in immune-competent rats, systemic administration of purified recombinant K1-3 resulted in up to 85% suppression of tumor growth (P = 0.011). Growth suppression was accompanied by a 32% decrease (P = 0.01) in tumor neovascularization. This study demonstrates a simple method to produce a biologically active recombinant angiostatin derivative. The ability to suppress intracerebral tumor growth after systemic administration suggests that K1-3 is likely to have therapeutic value in the treatment of malignant glial tumors.
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PMID:Simplified production of a recombinant human angiostatin derivative that suppresses intracerebral glial tumor growth. 1058 88

Glioblastoma multiforme is a highly malignant tumor that is extremely refractory to therapy. One reason is its highly invasive nature into brain tissue. Metalloproteinases and their inhibitors, plasminogen activators (PA) and their inhibitors and cathepsins are thought to be involved in invasion by tumor cells. In this study, we determined if the urokinase-type plasminogen activator (uPA) and/or the urokinase-type plasminogen activator receptor (uPAR) were responsible for the invasion activity of a human glioma cell line. We determined the invasion activity of a human glioma U251 cell line using an in vitro invasion assay system. A 2.4- to 5.8-fold increase in invasion activity was observed in the presence of basic fibroblast growth factor (bFGF) or transforming growth factor (TGF)-alpha. Northern blot analysis showed that bFCF and TGF-alpha treatment was associated with increases in cellular mRNA levels of uPA and uPAR. Zymographic activity correlated to mRNA levels of uPA and uPAR. Addition of an anti-uPAR monoclonal antibody significantly inhibited the invasion activity induced by bFGF- and TGF-alpha. Irsogladine, an inhibitor of uPA synthesis, also blocked the invasion activity. These observations suggest that uPA and its receptor have a role in the invasion process of human gliomas.
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PMID:Up-regulation of urokinase-type plasminogen activator and its receptor correlates with enhanced invasion activity of human glioma cells mediated by transforming growth factor-alpha or basic fibroblast growth factor. 1089 64

Angiostatin, a specific angiogenesis inhibitor, is an internal fragment of plasminogen, and can be generated in many systems mediated by different enzymes in vitro. The mechanism of angiostatin generation in vivo has not been well defined. Here we demonstrated that human glioma cell line BT325 can express an enzyme that can convert purified plasminogen to angiostatin-like fragments with molecular masses of 65, 60, and 58 kDa, respectively. These fragments have an identical N-terminal as KVYLS, which starts from Lys(98) of the plasminogen precusor. According to their molecular mass, the three fragments should comprise kringle domain 1 to kringle domain 5 (kringle 1-5). The proteolytic fragments obtained as above can inhibit the growth of bovine aortic endothelial (BAE) cells specifically. The proteolysis process can be completely inhibited by serine proteinase inhibitors, and partially inhibited by EDTA. The molecular weight of the peptide, which contains an enzymatic activity responsible for the proteolysis, was 13 kD determined by gel filtration and SDS-PAGE. The present data suggest that glioma cell BT325 can produce a novel proteinase to generate kringle 1-5 of plasminogen as an angiogenesis inhibitor.
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PMID:Human glioma cell BT325 expresses a proteinase that converts human plasminogen to kringle 1-5-containing fragments. 1109 91

Urokinase-type plasminogen (uPA) activator regulates a variety of processes, including morphogenesis, cell differentiation, migration, and invasion. In previous studies, we demonstrated that uPA levels are significantly higher in anaplastic astrocytoma and glioblastoma than in low-grade glioma and normal brain tissue. In the present study, our goal was to determine whether the increase in uPA production in higher-grade gliomas is caused by an increase in mRNA stability or increased transcription of the gene in three human glioma cell lines of various grades (H4, SW1783, UWR3). The half-life of uPA mRNA was about 14 h in UWR3 and 8 h in SW1783 cells. In transient transfection studies of the wild-type -2109-bp human uPA promoter in the different grades of cell lines, the uPA promoter activity was increased two-fold in SW1783, anaplastic astrocytoma cells and six-fold in UWR3 glioblastoma cells, as compared with the uPA promoter activity in low-grade H4 cells. Using human uPA promoter chloramphenicol acetyl transferase (CAT) constructs with mutations of the AP-1 element at -1967 or the PEA-3 cis element at -1973, the activity of the uPA promoter was decreased 4-fold to 10-fold in all three human glioma cell lines. In transient transfection assays, the uPA promoter was stimulated 2.2-fold in UWR3 and SW1783 cells and 3.7-fold in H4 cells in response to phorbol-12-myristat-13-acetate. We further studied the activation and inhibition of uPA promoter by co-expression of a transactivation domain lacking c-jun: a dominant negative ERK1 and ERK2 mutant and a dominant negative c-raf in glioblastoma cell line showed repressed uPA promoter activity compared with the effect of the empty expression vector. We conclude from our findings that increased transcription is the more likely mechanism underlying the increase in uPA production in high-grade gliomas.
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PMID:Regulation of the uPA gene in various grades of human glioma cells. 1111 41

The diffuse and extensive infiltration of malignant gliomas into the surrounding normal brain is believed to rely on modifications of the proteolysis of extracellular matrix components. A key molecule in regulating plasminogen-mediated extracellular proteolysis is the urokinase-type plasminogen activator (uPA). To investigate the role of uPA in the invasive process of brain tumors, we stably transfected a human glioblastoma cell line SNB19 with a vector capable of expressing an antisense transcript complementary to the 1020 bases at the 3' end of the uPA cDNA. Parental, vector-, and antisense construct-stably transfected cell lines were analyzed for uPA mRNA transcript by Northern blot analysis, for uPA enzyme activity by zymography, and for uPA protein levels by Western blotting. The levels of uPA mRNA, protein, and enzyme activities were significantly lower in antisense clones than in parental and vector controls. Radioreceptor binding studies demonstrated that uPA receptor levels remained the same in parental, vector-, and antisense-transfected cells. The antisense-transfected cells showed a markedly lower level of invasion in the Matrigel invasion assays, and their spheroids failed to invade the fetal rat brain aggregates in the coculture system. Green fluorescent protein (GFP) expressing parental and antisense transfectants was generated for detection in mouse brain tissue without any posttreatment. Intracerebral injection of antisense stable transfectants significantly reduced tumor formation compared with that in controls. Our results suggested that down-regulation of uPA expression may be a feasible approach to reducing the malignancy and invasiveness of glial tumors.
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PMID:Stable transfection of urokinase-type plasminogen activator antisense construct modulates invasion of human glioblastoma cells. 1148 35

Tumour cell invasion is a dynamic process that depends on a co-ordinated series of biochemical events. This review discusses the role of the proteolytic enzyme system, the plasminogen activation cascade, in glioma cell invasion.
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PMID:The role of the plasminogen activation cascade in glioma cell invasion: a review. 1263 39

The presence of reactive astrocytes around glioma cells in the CNS suggests the possibility that these two cell types could be interacting. We addressed whether glioma cells use the astrocyte environment to modulate matrix metalloproteinase-2 (MMP-2), a proteolytic enzyme implicated in the invasiveness of glioma cells. We found that astrocytes in culture produce significant amounts of the pro-form of MMP-2 but undetectable levels of active MMP-2. However, after coculture with the U251N glioma line, astrocyte pro-MMP-2 was converted to the active form. The mechanism of pro-MMP-2 activation in glioma-astrocyte coculture was investigated and was found to involve the urokinase-type plasminogen activator (uPA)-plasmin cascade whereby uPA bound to uPA receptor (uPAR), leading to the conversion of plasminogen to plasmin. The latter cleaved pro-MMP-2 to generate its active form. Furthermore, key components (i.e., uPAR, uPA, and pro-MMP-2) were contributed principally by astrocytes, whereas the U251N glioma cells provided plasminogen. In correspondence with this biochemical cascade, the transmigration of U251N cells through Boyden invasion chambers coated with an extracellular matrix barrier was increased significantly in the presence of astrocytes, and this was inhibited by agents that disrupted the uPA-plasmin cascade. Finally, using resected human glioblastoma specimens, we found that tumor cells, but not astrocytes, expressed plasminogen in situ. We conclude that glioma cells exploit their astrocyte environment to activate MMP-2 and that this leads to the increased invasiveness of glioma cells.
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PMID:Exploitation of astrocytes by glioma cells to facilitate invasiveness: a mechanism involving matrix metalloproteinase-2 and the urokinase-type plasminogen activator-plasmin cascade. 1276 90


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