Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017636 (glioblastoma)
 18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Connexins (cx), structural components of gap junction, are believed to play a role in the regulation of cell proliferation and suppression of the neoplastic phenotype. We used human brain glioblastoma tumor cells as a model system to test this hypothesis. Western blot and reverse transcription-PCR analysis indicate that the expression levels of the gap junction protein connexin 43 (cx43) are profoundly decreased in several human brain tumor cell lines examined. Transfection of human cx43 into human glioblastoma cell lines U251 and T98G profoundly reduces cell proliferation in monolayer culture, in soft agar, and in athymic nude mice. Surprisingly, these effects are not associated with the establishment of gap junction communication in cx43 transfected cells. We conclude that the loss of cx43 expression may play a role in the development of human gliomas and that cx43 acts as a tumor suppressor gene to human glioblastoma.
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PMID:Reversion of the neoplastic phenotype of human glioblastoma cells by connexin 43 (cx43). 982 17

In tumors, gap junctional intercellular communication (GJIC) is usually down-regulated and the expression of connexins, membrane proteins constituting gap junction channels, is often low or altered. GJIC, allowing the intercellular diffusion of ganciclovir (GCV) triphosphate, is also one mediator of the 'bystander effect', the phenomenon by which herpes simplex virus thymidine kinase (HSVtk)-transduced, neoplastic cells kill surrounding HSVtk-negative cells when treated with GCV. We set up experiments to evaluate the effects of retrovirus-mediated in vivo gene transfer of connexin 43 in malignancies with low GJIC capacity. We found that U-87 human glioblastoma cells transfected in vitro by the human Cx43 cDNA grow significantly more slowly than control U-87 cells and lose their tumorigenicity when injected subcutaneously in nude mice. When the Cx43 gene was transduced in vitro in U-87 cells by a retroviral producer cell line (N3.2.ii, titer 1.5 x 10(6) c.f.u./ml) in vivo results were similar. However, only when U-87 cells were co-injected with N3.2.ii cells in nude mice in a 1:5 ratio, a 50% reduction in tumor size was obtained during the first 3 weeks. Moreover the coinjection of U-87 cells with N3.2.ii and SBA cells (a retroviral producer cell line expressing the HSVtk gene), was not able to potentiate the effects of GCV administration, suggesting that Cx43 gene transfer requires more efficient vectors to increase the bystander effect in vivo.
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PMID:In vitro and in vivo effects of retrovirus-mediated transfer of the connexin 43 gene in malignant gliomas: consequences for HSVtk/GCV anticancer gene therapy. 993 Mar 23

Transforming growth factor (TGF) beta1 enhanced in vitro [3H]thymidine incorporation into C6 cells and reduced that of astrocytes in the presence of a high serum concentration. It concomitantly raised the gap junction intercellular communication (GJIC) in normal astrocytes but reduced the coupling of C6 cells, and respectively increased or decreased the proportion of P2-phosphorylated connexin (Cx) 43 isoform in these cells. Finally, octanol, which inhibited GJIC in both cell types, increased the thymidine incorporation in C6 cells, but neither altered the proliferation of astrocytes nor their response to TGFbeta1. These data indicate that an inhibition of gap junction intercellular communication, due to an altered phosphorylation of connexin 43, may contribute to the proliferative response of C6 glioblastoma cells to TGFbeta1.
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PMID:Growth regulation of astrocytes and C6 cells by TGFbeta1: correlation with gap junctions. 1100 51

To investigate the factors influencing the bystander effect--a key element in the efficacy of suicide gene therapy against cancer--we compared the effect triggered by four extremely efficient gene/prodrug combinations, i.e., VZVtk/BVDU, the thymidine kinase of Varicella zoster virus associated with (E)-5-(2-bromovinyl)-2'-deoxyuridine; VZVtk/BVaraU, the same enzyme associated with (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil; HSVtk/BVDU, the association of the Herpes simplex virus thymidine kinase with BVDU; and the classical HSVtk/GCV (ganciclovir) paradigm. The cells used, the human MDA-MB-435 breast cancer, and the rat 9L glioblastoma lines were equally sensitive in vitro to these four associations. In both cell types, the combinations involving pyrimidine analogues (BVDU, BVaraU) displayed a smaller bystander killing than the combination involving the purine analogue (GCV). In addition, the bystander effect induced by all the tk/prodrug systems was reduced in MDA-MB-435 cells in comparison to 9L cells; albeit, the viral kinases were produced at a higher level in the breast cancer cells. All systems induced apoptotic death in the two cell types, but the MDA-MB-435 cells, deprived of connexin 43, were noncommunicating in striking contrast with the 9L cells. That functional gap junctions have to be increased in order to improve the breast cancer cell response to suicide gene therapy was demonstrated by transducing the Cx43 gene: this modification enhanced the bystander effect associated in vitro with GCV treatment and, by itself, decreased the tumorigenicity of the untreated cells. However, the noncommunicating MDA-MB-435 cells triggered a significant bystander effect both in vitro and in vivo with the HSVtk/GCV system, showing that communication through gap junctions is not the only mechanism involved.
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PMID:The role of cellular- and prodrug-associated factors in the bystander effect induced by the Varicella zoster and Herpes simplex viral thymidine kinases in suicide gene therapy. 1112 88

Stable re-expression of connexin 43 (cx43) in human glioblastoma suppresses transformation and tumorigenicity. The present study was designed to examine the role of cx43 in chemotherapy-induced apoptosis. Expression of cx43 in human glioblastoma cells significantly increased sensitivity to several common chemotherapeutic agents, including etoposide, paclitaxel (Taxol) and doxorubicin, compared with control-transfected cells. The increased sensitivity to chemotherapeutic agents resulted from apoptosis as evidenced by Hoechst dye staining, TUNEL assay and annexin V assay. These cx43-mediated effects were coupled with decreased expression of the specific apoptosis inhibitor bcl-2. Over-expression of bcl-2 in cx43-transfected cells partially confers the resistance to apoptosis induced by etoposide, suggesting that the cx43-mediated apoptosis to chemotherapeutic agents is regulated in part through the down-regulation of bcl-2 expression. Furthermore, the cx43-mediated apoptosis in response to chemotherapeutic drugs may not be linked to increased gap junctional communication in cx43-transfected cells. Our results demonstrate a new role of cx43 in the mediation of apoptosis during chemotherapy.
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PMID:Connexin 43 (cx43) enhances chemotherapy-induced apoptosis in human glioblastoma cells. 1127 16

Previously, we demonstrated that connexin 43 (cx43) suppressed the growth of human glioblastoma cells. To investigate the molecular mechanisms involved in tumor suppression by cx43, we developed a human cytokine array system, which simultaneously detects the expression of 43 cytokines. By using this new technology, we analyzed the cx43-regulated genes in cx43-transfected cells. The cytokine arrays showed that expression of monocyte chemotactic protein-1 (MCP-1) was profoundly reduced in cx43-transfected cells. RT-PCR, immuno-Western blot, and cDNA microarrays further confirmed this observation. Addition of conditioned medium from control-transfected cells and recombinant MCP-1 to cx43-transfected cells significantly enhanced cx43-transfected cell proliferation and colony formation in soft agar. In contrast, addition of neutralization antibody against MCP-1 significantly inhibited cell proliferation in control-transfected cells. Our results suggested that MCP-1 is involved in the suppression of human glioblastoma cell growth by cx43.
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PMID:Connexin 43 suppresses human glioblastoma cell growth by down-regulation of monocyte chemotactic protein 1, as discovered using protein array technology. 1201 57

The ability of herpes simplex virus type 1 thymidine kinase (HSV-tk)-expressing cells incubated with ganciclovir (GCV) to induce cytotoxicity in neighboring HSV-tk-negative (bystander) cells has been well documented. Although it has been suggested that this bystander cell killing occurs via the transfer of phosphorylated GCV, the mechanism(s) of this bystander effect and the importance of gap junctions for the effect of prodrug/suicide gene therapy in primary human glioblastoma cells remains elusive. Surgical biopsies of malignant gliomas were used to establish explant primary cultures. Proliferating tumor cells were characterized immunohistochemically and found to express glial tumor markers including nestin, vimentin, glial fibrillary acidic protein (GFAP), S-100, and gap junction protein connexin 43 (Cx43). Western blot analysis revealed the presence of phosphorylated isoforms of Cx43 and Calcein/DiI fluorescent dye transfer showed evidence of efficient gap junction communication (GJC). In order to study the effect(s) of prodrug/suicide gene therapy in these cultures, human glioblastoma cell cultures were transfected with the HSVtk gene for transient or stable expression. Ganciclovir treatment of these cultures led to >90% of cells dead within 1 week. Eradication of cells could be inhibited by the addition of alpha-glycyrrhetinic acid (AGA), a GJC inhibitor. In parallel experiments, AGA decreased the immunodetection of phosphorylated Cx43 as analyzed by Western blot and inhibited fluorescent dye transfer. In conclusion, these observations are consistent with GJC as the mediator of the bystander effect in primary cultures of human glioblastoma cells by the transfer of phosphorylated GCV from HSVtk gene transfected cells to untransfected ones.
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PMID:Gap junction-mediated bystander effect in primary cultures of human malignant gliomas with recombinant expression of the HSVtk gene. 1265 Nov 52

Human glioblastoma cell cultures were established and the expression of glial fibrillary acidic protein (GFAP) and the gap-junction protein connexin 43 (Cx43) was confirmed by Western blot. Following treatment with 4-phenylbutyrate (4-PB), increased concentrations of non-phosphorylated GFAP were seen, while phosphorylated isoforms remained intact. Immunocytochemical staining of glioblastoma cells revealed an intracellular redistribution of GFAP. In addition to cytoplasmic immunostaining, GFAP immunoreactivity was also associated with the nucleus and/or the nuclear membrane. Phosphorylated and non-phosphorylated Cx43 proteins were increased 2- to 5-fold following 4-PB treatment, and were redistributed to areas of the cell surface, participating in cell-to-cell contacts. In addition, functional gap-junction coupling was amplified, as indicated by increased fluorescent dye transfer, and elevated levels of Cx43 protein were detected in parallel with enhanced gap-junction communication. Induced cell differentiation, with improved functional coupling of tumour cells, may be of importance for therapeutic strategies involving intercellular transport of low molecular-weight compounds.
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PMID:Histone deacetylase inhibitor 4-phenylbutyrate modulates glial fibrillary acidic protein and connexin 43 expression, and enhances gap-junction communication, in human glioblastoma cells. 1509 85

Gene therapy of glioma based on viral delivery of herpes simplex virus type I thymidine kinase (HSV-TK) has failed in the clinic because of low transduction efficacy. To circumvent this problem, this study evaluated highly migratory HSV-TK-transduced neural stem cells (NSC) for their ability to kill untransduced glioma cells by a gap junction-mediated bystander effect. The admixture of HSV-TK-transduced NSC to U87MG and LN-18 human malignant glioma cell lines at ratios of 1:10 or 1:1 eliminated more than 50% or 90% of glioma cells in the presence of ganciclovir (25 microM). Glioma cell cytotoxicity required cell-cell contact. Similarly, tumor cell cytotoxicity was observed in two of three primary glioblastoma cell cultures, and the presence of this bystander effect correlated with the expression of connexin 43 in the untransduced glioma target cells. In conclusion, we delineate a role for migratory HSV-transfected NSC to eliminate glioma cells purely by means of the bystander effect.
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PMID:Migratory neural stem cells for improved thymidine kinase-based gene therapy of malignant gliomas. 1567 Jul 59

Glioblastoma is a highly malignant tumor, characterized by an unfavorable prognosis even in response to multidisciplinary treatment strategies, owing to its high-invasive phenotype. Ukrain, a semisynthetic thiophosphoric acid derivative of the purified alkaloid chelidonine, has been used in the therapy of several solid tumors, but little is known about its effect on glioblastoma and, in general, about the molecular mechanisms responsible for its effects. In particular, we previously demonstrated that Ukrain modulates the expression of genes and proteins involved in tumor invasion, and here we investigate some unreported effects of Ukrain on human cultured glioblastoma cells. We used morphological and molecular biology methods to analyze the expression and the intracellular distribution pattern of glial fibrillary acidic protein, the expression of the gap junction protein connexin 43 and the apoptotic effect in human glioblastoma cells treated with 0.1, 1 and 10 micromol/l Ukrain for 72 h. After treatment with 10 micromol/l Ukrain, glial fibrillary acidic protein fluorescence increased and a higher number of cells displayed glial fibrillary acidic protein organized into a filamentous state. Western blot analysis of glial fibrillary acidic protein confirmed that Ukrain tended to upregulate the protein. Connexin 43 was not modulated by Ukrain both at the mRNA and at the protein level. Ukrain-induced apoptotic rate was 4.63, 10.9 and 28.9% after 0.1, 1 and 10 micromol/l Ukrain, respectively, likely mediated by cytochrome c release in the cytoplasm. Considered as a whole, these findings provide new information to complete the understanding of the mechanisms of Ukrain antitumor and chemopreventive effect, and support the possible potential of Ukrain for the therapy of brain tumors.
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PMID:Ukrain modulates glial fibrillary acidic protein, but not connexin 43 expression, and induces apoptosis in human cultured glioblastoma cells. 1776 95


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