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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The U-373 MG glioblastoma and the IMR-32 neuroblastoma cell lines were found to express the dopamine (DA) and vesicular monoamine transporters, using reverse transcriptase-polymerase chain reaction (RT-PCR). To further characterize the DA transporter, [3H]GBR-12935 binding and [3H]DA uptake studies were performed. Specific binding of [3H]GBR-12935 to U-373 MG and IMR-32 cells is saturable as saturation experiments indicated. Scatchard analysis revealed two binding sites on U-373 MG as well as on IMR-32 cells. The high-affinity sites exhibited a KD of 2.95 and 0.42 nM and a Bmax of 6.4 and 0.83 fmol/mg protein for U-373 MG and IMR-32 cells, respectively. The low-affinity sites exhibited a KD of 144 and 251 nM and a Bmax of 37.5 and 119 fmol/mg protein for the same cells, respectively. The high-affinity binding of both types of cells probably represents the "classic" DA uptake site identified in other studies from human and rat striatal membranes or synaptosomes, while the low-affinity binding may represent a mazindol-insensitive binding site (the "piperazine acceptor site"). [3H]DA uptake was 0.55 +/- 0.16 and 1.08 +/- 0.33 pmol/mg protein for U-373 MG and IMR-32 cells, respectively. Since the DA transporter has been implicated as an important site for drugs and toxins, the above-mentioned cell lines may be a useful tool in the study of the mechanism of action of DA transporter modulating substances.
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PMID:U-373 MG glioblastoma and IMR-32 neuroblastoma cell lines express the dopamine and vesicular monoamine transporters. 884 87

Synthetic oligodeoxyribonucleotides (ODNs) designed to selectively inhibit the transcription or translation of specific genes are being used to modulate the activity of the targeted gene. Because multiple copies of mRNA can be transcribed from one actively expressed gene, ODNs that target double-stranded DNA and form triple helices upon binding with the gene itself have an advantage over ODNs that target the gene product (mRNA) in an antisense fashion. For the present studies, we designed four different triple helix-forming phosphodiester ODNs (TFOs) targeted to the tumor necrosis factor (TNF) gene and examined their effect on production of TNF and on cellular growth of tumors in which TNF acts as an autocrine growth factor. The ODNs J-109-50 and J-108-57 were designed to interact with polypurine oligonucleotides corresponding to the binding sites for nuclear factors kB (-237 to -208) and Sp1 (-58 to -33), respectively; J111-51 was designed to interact with a polypurine oligonucleotide in the third intron (+1429 to +1456) of the TNF gene. To enhance the cellular penetration and prevent degradation by cellular nucleases, the TFOs were modified at their 3' ends by either a cholesterol side chain or a propanolamine blocking group. Treatment of the human promonocytic cell line THP-1 with TNF-TFOs at a nontoxic concentration (2 microM) reduced the production of TNF. All of the TNF-TFOs tested were effective, and control-irrelevant TFOs were ineffective in inhibiting TNF production. The activity of the most efficacious TNF-TFOs also correlated with a decrease in TNF mRNA as observed by using reverse transcriptase PCR assays. In several tumors in which TNF acts as an autocrine growth factor, we examined the antiproliferative activity of J111-51. We found that in the human glioblastoma tumor cell line U-251, TNF-induced growth was blocked by J111-51 in a dose-dependent manner. Thus, overall results demonstrate that oligonucleotides directed to the specific regions of TNF can be designed, which may have a potential in cancer therapy.
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PMID:Triple helix-forming oligodeoxyribonucleotides targeted to the human tumor necrosis factor (TNF) gene inhibit TNF production and block the TNF-dependent growth of human glioblastoma tumor cells. 891 51

Effective treatment is lacking for malignant glioblastoma/astrocytoma. We have identified interleukin-4 receptors (IL-4R) on human malignant astrocytoma. We demonstrate that 16 of 21 surgical samples of high-grade astrocytoma and glioblastoma but not normal brain tissues expressed IL-4R as assessed by reverse transcriptase PCR. We further demonstrate that human malignant astrocytoma cell lines express high-affinity IL-4R. Using a chimeric protein composed of circularly permuted IL-4 and a truncated form of Pseudomonas exotoxin A, we observed that this toxin IL4(38-37)-PE38KDEL) is highly cytotoxic to IL-4R-bearing glioblastoma cells. Compared with a previously reported IL4-PE chimeric protein (IL-PE4E), IL4(38-37)-PE38KDEL bound with higher affinity and was 3-30-fold more cytotoxic to glioblastoma cell lines. Upon intrathecal administration in monkeys, high cerebrospinal fluid IL4(38-37)-PE38KDEL levels were achieved using 2- and 6-microg/kg doses without any central nervous system or other abnormalities. IL4(38-37)-PE38KDEL levels were not detectable in the serum of any monkey studied. When IL4(38-37)-PE38KDEL was injected into the right frontal cortex of rats, localized necrosis was observed at 1000-ng/ml doses but not at < or = 100-ng/ml doses. We conclude that by localized administration, nontoxic levels of IL4(38-37)-PE38KDEL can be achieved, which may have significant cytotoxic activity against malignant astrocytoma.
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PMID:Preclinical development of a recombinant toxin containing circularly permuted interleukin 4 and truncated Pseudomonas exotoxin for therapy of malignant astrocytoma. 1145 21

We have cloned the cDNA encoding the voltage-dependent K+ channel Kv2.1 from human brain (hKv2.1). RNase protection and RT-PCR (reverse transcriptase-PCR) experiments reveal abundant Kv2.1 transcripts in human brain with virtually no expression detectable in human heart. hKv2.1 has been stably transfected into a human glioblastoma cell line, and transformed cells display large, slowly activating outward currents. The kinetics, steady-state activation and inactivation parameters, and external tetraethylammonium sensitivity were all similar to those described previously for hKv2.1 channels transiently expressed in Xenopus oocytes or other mammalian cell lines. A number of dopamine receptor antagonist/antipsychotic agents were shown to block hKv2.1. Trifluoperizine, trifluperidol and pimozide produced time-dependent blockade of hKv2.1 with IC50 values of approx. 1-2 microM. The diphenylbutylpiperidine fluspirilene was shown to be 4-5-fold more potent than the other agents tested inhibiting hKv2.1 current with an IC50 value of 297 nM. The block produced by fluspirilene was both time- and frequency-dependent. Furthermore, fluspirilene (1 microM) shifted the midpotential of the hKv2.1 steady-state inactivation curve by approx. 15 mV in the hyperpolarizing direction. These results demonstrate the usefulness of this transfection system for the pharmacological characterization of hKv2. 1. Fluspirilene proved to be a relatively potent blocker of hKv2.1 and may provide a useful starting point for the development of more potent and selective agents active against this brain K+ channel.
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PMID:Stable expression and characterization of the human brain potassium channel Kv2.1: blockade by antipsychotic agents. 924 64

To characterize the expression and localization of interleukin (IL)-1beta in human gliomas, both reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry were used on surgically excised human gliomas, human malignant glioma xenografts, and human glioblastoma cell lines. The RT-PCR products for IL-1beta mRNA were quantified by computerized image analysis. IL-1beta mRNA was detectable in 30 out of 35 (86%) surgically resected gliomas. An abundant expression of IL-1beta mRNA was often found in the glioblastomas, anaplastic astrocytomas, and pilocytic astrocytomas, but not in other types of gliomas. Quantitatively, in both the grade 2 astrocytomas and the oligodendrogliomas, the IL-1beta mRNA levels were significantly (p < 0.05) lower than those of the grade 3/4 astrocytomas. Immunohistochemically, IL-1beta was localized in the pleomorphic tumor cells of the astrocytic tumors and in macrophages. In contrast to the astrocytic tumors, low and high grade oligodendrogliomas showed no or little expression of IL-1beta antigen. IL-1beta was present less frequently than IL-1alpha and IL-1 receptor type 1 in 4 malignant gliomas transplanted into nude mice by RT-PCR. All 2 cell lines showed IL-1beta expression at both the mRNA and protein levels. It is concluded that in human gliomas, both high-grade astrocytomas and pilocytic astrocytomas often express high IL-1beta production, and that IL-1beta is mainly localized in astrocytic tumor cells and macrophages.
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PMID:Expression of interleukin-1beta mRNA and protein in human gliomas assessed by RT-PCR and immunohistochemistry. 969 Jun 69

Low-density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP) has been proposed to mediate the cellular uptake and clearance of inactivated protease-inhibitor complexes in regulating proteinase activity at the cell surface, which is necessary for cellular migration and invasive processes. In this study, we investigated the presence of both LRP and urokinase-type plasminogen activator receptor (uPAR) in glioblastoma by reverse transcriptase-polymerase chain reaction (RT-PCR), and the cellular localization of LRP in glioblastoma tissues by immunohistochemical analysis. LRP mRNA was frequently expressed in glioblastomas and anaplastic astrocytomas compared with low-grade astrocytomas by RT-PCR analysis, and was well correlated with uPAR expression. The immunohistochemistry of LRP on sequential frozen sections showed that neoplastic glial cells and endothelial cells of glioblastomas exhibited intense LRP immunoreactivity, whereas LRP was almost undetectable in low-grade astrocytomas or in normal glial cells and endothelial cells of normal brain tissue. Glioblastomas from 11 patients in which the expression of LRP mRNA was observed by PCR displayed strong to moderate LRP immunoreactivity, with predominantly diffuse cytoplasmic and cell-surface localization. In normal brain tissues, LRP immunoreactivity was identified in the pyramidal neurons of the cerebral cortex. These results indicate that LRP is present both in the cellular cytoplasm and on the cell surface of glioblastomas with an increased expression of uPAR. Altered LRP expression might contribute to the stimulation of cell-surface proteolytic activity that in turn facilitates the invasiveness of glioblastoma in vivo.
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PMID:Expression and cellular localization of low-density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor in human glioblastoma in vivo. 987 60

Glial cell line-derived neurotrophic factor (GDNF), a sequence-related factor of the transforming growth factor-beta family, has been identified as a potent neurotrophic factor for a variety of neuronal cell populations. At present, it is still unknown whether human gliomas in vivo are also capable of producing GDNF. We studied the expression of GDNF in 14 human glioblastomas, 1 gliosarcoma and 5 astrocytomas. Using an enzyme-linked immunosorbent assay, the amount of GDNF was quantified in human gliomas and compared to GDNF-expression in C6 glioma cells, mouse fibroblasts and normal human and rat brain. Mean concentration of GDNF in gliomas was 937 +/- 140 pg GDNF/g tissue (n = 20). C6 cells revealed the highest expression levels of 2,837 +/- 813 pg/g, whereas mouse 3T3 fibroblasts showed no detectable GDNF protein. Mean GDNF tissue levels in normal human and rat brain were significantly lower. Using reverse transcriptase-polymerase chain reaction, GDNF mRNA was detected in human gliomas and in rat C6 cells. Immunohistochemistry revealed strong GDNF- and GDNF receptor-alpha 1-expressing tumor cells in human glioma tissue. These results show that glial tumors, even in the most dedifferentiated form of glioblastoma, express GDNF at concentrations up to five times higher compared to normal human brain. This overexpression of GDNF may be of biological relevance for proliferation of glial tumors in humans.
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PMID:Glial cell line-derived neurotrophic factor (GDNF) and its receptor (GFR-alpha 1) are strongly expressed in human gliomas. 1067 19

Thymidine phosphorylase (TP) has been implicated as a potent angiogenic factor and a prognostic factor in various human solid tumors. We investigated the expression of TP in a series of human astrocytic tumors using immunohistochemistry, enzyme-linked immunosorbent assay, and reverse transcriptase/polymerase chain reaction (RT-PCR) analysis. A total of 63 astrocytic tumors [27 glioblastomas (GBM), 19 anaplastic astrocytomas (AA), 17 low-grade astrocytomas (LGA)] and 5 normal brain tissues were immunohistochemically stained with antibodies to TP, vascular endothelial growth factor (VEGF), p53, MIB-1, and factor-VIII-related antigen. They were also evaluated for the degree of apoptosis by a ApopTag kit. Ten tumors (5 GBM, 2 AA, 3 LGA) and 3 normal brain tissues were evaluated for their expression of VEGF and TP by RT-PCR analysis. TP was constantly localized in the cytoplasm of astrocytic tumor cells, less intensely in the cytoplasm of vascular endothelial cells, but not in the normal brain. Some of the TP-positive cells were of macrophage origin, but most positive cells were the tumor cells themselves. Vascular density, MIB-1 positivity, p53 positivity, VEGF expression, and the apoptotic index were significantly higher in the TP-positive tumors than in TP-negative tumors. There was a significant correlation between TP and VEGF mRNA expression. In a limited number of glioblastoma cases, the apoptotic index was significantly higher in TP-positive glioblastomas than in TP-negative glioblastomas. In human astrocytic tumors, TP was expressed in the tumor, macrophage, and endothelial cells. TP was a potent angiogenic factor closely associated with cell proliferation and tumor apoptosis.
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PMID:Expression of the angiogenic factor thymidine phosphorylase in human astrocytic tumors. 1074 8

The type III deletion mutant of the epidermal growth factor receptor (EGFR) is a potential target in diagnostic and therapeutic approaches for those glioblastomas characterized by its expression. We previously raised a mouse monoclonal antibody, 3C10 (IgG2b) specifically recognizing this mutant EGFR. In this study, a single-chain variable fragment (scFv) antibody was produced. Partial determination of its N-terminal amino acid sequence and preparation of adequate primers for variable heavy chain (V(H)) and variable light chain (V(L)) genes were performed to allow cloning by means of reverse transcriptase-polymerase chain reaction. The genes cloned were assembled with a linker, (Gly4Ser)3, and ligated into a bacterial expression vector to express the scFv as cytoplasmic inclusion bodies. After appropriate refolding, the antibody activity of the V(H)-V(L) scFv was examined in an enzyme-linked immunosorbent assay. 3C10 scFv showed a selective reactivity with the mutant peptide, similarly to the parental 3C10 antibody. A mouse transfectant expressing the type III mutant EGFR and a glioblastoma with type III deletion-mutant EGFR were positively stained by immunofluorescence. By Biacore analysis, the affinity (K(A)) of the parental 3C10 for the mutant peptide was 9.7 x 10(7) M(-1), while that of 3C10 scFv was 2.45 - 2.48 x 10(7) M(-1), being approximately 4-fold weaker. The results together suggested that the scFv antibody retained the appropriate structure to recognize a conformational epitope of the mutant receptor, similarly to the parental antibody.
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PMID:Production of a single-chain variable fragment antibody recognizing type III mutant epidermal growth factor receptor. 1105 Apr 75

Production and secretion of endothelin-1 (ET-1) by a human glioblastoma cell line, T98G, were studied by radioimmunoassay and Northern blot analysis. Immunoreactive ET was detected in the culture medium of T98G (17.6 +/- 0.6 fmol/10(5) cells/24 h, mean +/- SEM, n = 5). Reverse-phase high-performance liquid chromatography (HPLC) of immunoreactive ET in the culture medium extract showed a single peak eluting in the position of ET-1. Northern blot analysis showed expression of ET-1 mRNA in T98G cells. Treatment with interferon-gamma decreased the expression of ET-1. Treatment with TNFalpha or interleukin-1beta (IL-1beta) increased the expression of ET-1. Furthermore, reverse transcriptase polymerase chain reaction (RT-PCR) showed expression of endothelin-A- and -B- (ET(A) and ET(B)) receptor mRNAs in T98G glioblastoma cells. These findings indicate that glioblastoma cells produce and secrete ET-1, and express ET receptor mRNAs. ET-1 secreted by glioblastoma cells may act locally on tumor cells, possibly as a growth modulator.
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PMID:Expression of endothelin-1 and endothelin receptors in cultured human glioblastoma cells. 1107 29


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