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: UMLS:C0017636 (glioblastoma)
18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The construction of a new retroviral vector, pSKV, is described. This vector carries two unique cloning sites, located between two Moloney leukemia virus-derived LTR, into which genes of interest may be introduced. The gene encoding hygromycin resistance (HyR) was subsequently introduced into one of the two sites, producing a second vector (pSKV/HyR) containing a unique SfiI site for the introduction of cDNA clones under the control of the cytomegalovirus (CMV) promoter (P-CMV). The cDNA (mH13), encoding a protein that has been shown to serve as a murine ecotropic retroviral receptor in transient assays, was cloned into the SfiI site (pSKV/HyR/mH13). Both constructs can be packaged into retroviral particles following transfection into an appropriate packaging cell line. Stable transfectants of the human glioblastoma cell line (U118MG) carrying each of these two constructs were generated by transfection and subsequent Hy selection. Clones expressing both the selectable marker and the mH13 gene, but not those expressing only the selectable marker, are shown to be susceptible to infection with murine ecotropic retroviral particles. These cells (HyR and mH13 positive) were then exposed to CRE/Xtk culture supernatant, a packaging cell line producing ecotropic retroviral particles carrying the HSV-TK (Herpes simplex virus-thymidine kinase) and neoR (neomycin-resistance) genes. Selection was in the presence of G418. In vitro growth of the U118MG/HyR/mH13/TK cells, but not that of the U118MG/HyR/mH13 cells, was inhibited by ganciclovir (GCV), indicating the successful transfer of HSV-TK by infection of human cells with murine retroviruses via the mH13 product.
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PMID:Infection of human cells by murine ecotropic viruses: retroviral vectors carrying the hygromycin resistance-encoding gene. 866 55

Four different transcripts encoding fibroblast growth factor 1 (FGF-1, also known as aFGF) have been previously identified in our laboratory. Among them, FGF-1.B is the major transcript expressed specifically in the neuronal cells in brain tissue. Using the transient transfection experiment in a glioblastoma cell line, U1240MG, that expresses 1.B, we previously identified two regulatory regions (RR1 and RR2) in the brain-specific promoter, FGF-1.B. In the present study, we showed that the minimal region required for the DNA-protein interaction in RR2 resides in an 18-base pair (-484 to -467) sequence, by using DNase I footprinting and methylation interference studies and electrophoretic mobility shift assays. This minimal cis-acting element was found to be sufficient in enhancing the reporter activity driven by the heterologous herpes simplex virus thymidine kinase promoter in the 1.B-positive U1240MG cell line. This enhancing effect, however, was not detected in a glioblastoma cell line, U1242MG, which is negative for 1.B expression. By electrophoretic mobility shift assays, we also identified a specific DNA-protein complex, namely complex I, which is specific for 1.B-positive cell lines and human brain tissue. By in situ UV cross-linking experiment, we further showed that complex I contains two major DNA-binding proteins of apparent molecular masses of 37 and 98 kDa. Our results suggest that the formation of complex I, resulting from the heterodimerization of a 37-kDa protein (1.B-specific) and a 98-kDa protein (ubiquitous) may likely be a prerequisite for the enhanced expression of 1.B transcript in neuronal cells.
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PMID:Transcriptional activation of fibroblast growth factor 1.B promoter is mediated through an 18-base pair cis-acting element. 905 60

The authors have used the thymidine kinase/ganciclovir system to block glioblastoma multiforme neoplastic cells in vivo, both in experimental animals and in two patients in which the more conventional therapies had been unsuccessful. In the Wistar rat it was found that the curability potential of the system is correlated with tumoral volume. Tumours smaller than 20 mm3 can be cured with defective retrovirus that do not carry the Herpes simplex thymidine kinase (Hsvtk) gene. While tumours smaller than 150 mm3 can regress totally by the kinase/ganciclovir system, those above that size cannot be cured by this treatment. In humans the situation seems very similar in that the authors have been unable either to reduce the tumour size of recurrent patients with tumour volumes larger than 100 cm2 applying the standard thymidine kinase/ganciclovir gene therapy or to prolong their survival time more than 8 months [7]. When a combination of size reduction by neurosurgery and gene therapy was used the survival time increased considerably. Two patients have been treated by partial surgery and repeated treatment with thymidine kinase/ganciclovir through an Ommaya reservoir connected to a catheter leading into the tumour cavity. The magnetic resonance imaging (MRI) of these patients show only a residual tumoral growth along side the tumoral bed. The procedure may be partially controlling the proliferation of cancerous cells, because, these two patients having recurrent glioblastoma, are alive 11 and 17 months after the beginning of the treatment.
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PMID:Gene therapy in brain tumours: implications of the size of glioblastoma on its curability. 923 25

A promising strategy in the treatment of malignant gliomas involves the creation of Herpes Simplex Virus-thymidine kinase (HSV-tk) modified tumor cells. Some authors have observed complete tumor regression after ganciclovir (GCV) treatment of established gliomas transduced in vivo by the HSV-tk gene. Yet, further investigations did not confirm completely these results, even if confirmed the therapeutic potential of such a therapy. Using the rat C6 glioblastoma as a model of malignant brain tumor, we investigated the efficacy of in vivo and in vitro transduction of growing brain tumors with the HSV-tk gene, followed by GCV administration. The stereotactic injection into the left striatum of C6 cells mixed with retroviral producer cells and GCV treatment did not improve significantly the animal survival compared to controls. On the contrary, there was a significant prolongation of the survival of rats inoculated with C6 cells engineered in vitro to express the HSV-tk gene. Nevertheless, complete eradication of the tumors was not achieved. We also injected a group of six rats with a mixture of cells expressing the murine Interleukin-4 (IL-4) gene and C6 cells. IL-4 has been shown to produce the regression of experimental brain tumors. Our preliminary experience seems to confirm that hypothesis. Our results indicate that the outcome of HSV-tk gene therapy can be limited not only by low gene transfer but also by insufficient delivery of GCV to tumor cells. Combined strategies, based on contemporary transduction of HSV-tk and IL-4, may enhance the therapeutic perspectives of such a therapy.
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PMID:Perspectives for the gene therapy of malignant gliomas by suicide gene transfer. 944 75

Tumor cells transduced with retrovirus carrying the herpes simplex-1 virus thymidine kinase (HSV-tk) are capable of transforming the antiviral drug ganciclovir (GVC) into a metabolic form only toxic to dividing cells. The efficiency of this suicide gene therapy is increased by a "bystander" effect resulting not only in the death of the recipient cell, but also in the death of non modified surrounding cells. Even though the mechanism of this "bystander" effect remains to be elucidated, strong evidence suggest that the immune system plays a main role to achieve complete tumor eradication. In the present study we evaluate the efficiency of this suicide system on three different tumor models: one human melanoma, one murine melanoma, and a rat glioblastoma. Tumors were established by injection of tumor cells s.c. in nude and C57Bl/6 mice, respectively, and stereotactically into the brain of Sprague Dawley rats. Animals in the treated group were co-injected with packaging cells producing recombinant retrovirus carrying the HSV-tk gene, and followed by i.p. administration of GVC. In short term studies, we observed inhibition of tumor growth for all the tumor models evaluated (p < 0.01). In long term studies, using the C6 rat glioma line, 50% of the animals survived longer than 75 days (p < 0.0001), and were able to reject a contralateral challenges with C6 parental cells. Histological and immunohistochemical analysis showed the presence at an inflammatory infiltrate composed by T lymphocytes, macrophages and polymorphonuclear cells. These data demonstrate that suicide genes might represent an attractive form of cancer gene therapy in the treatment of brain tumors and their intracerebral dissemination.
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PMID:[Antitumor gene therapy using suicide genes]. 970 53

Four patients affected by glioblastoma recurrence were treated with a gene therapy-immunotherapy protocol consisting of intratumoral injections of culture cells producing a retroviral vector which expresses human interleukin-2 and the herpes simplex virus thymidine kinase genes. Seven to 14 days after implantation, the patients were treated with ganciclovir at standard doses. Anatomopathological and immunohistochemical data confirm the efficacy of transduction. From the clinical point of view, gene therapy combined with immunotherapy demonstrated safety and a short-range but clearcut oncolytic effect.
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PMID:Gene stereotactic neurosurgery for recurrent malignant gliomas. 971 24

Enzyme-prodrug therapy using ganciclovir and herpes simplex virus-thymidine kinase (HSV-TK) has demonstrated excellent antitumor activity in many different types of malignant cells. Previously, we noted that ganciclovir was substantially more cytotoxic than other HSV-TK substrates. Therefore, we embarked on a study to determine the basis for the superior cytotoxicity of ganciclovir. In U251tk human glioblastoma cells that stably express HSV-TK, ganciclovir elicited a >4 log cell kill instead of the < or =1.5 log cell kill mediated by two other HSV-TK substrates, 1-beta-D-arabinofuranosylthymine (araT) and acyclovir. Study of the metabolism of these drugs demonstrated that acyclovir was poorly phosphorylated to its active triphosphate with DNA incorporation below the limit of detection, which may explain the < 1 log cell kill in these cells. Lower levels of ganciclovir triphosphate accumulated compared with araT triphosphate (araTTP) under conditions that induced < or =1 log cell kill (67 versus 1235 pmol/10(7) cells, respectively), and the half-life for the triphosphate of ganciclovir was shorter than that of araT (terminal half-lives of 15 and 41 h, respectively). Incorporation of ganciclovir monophosphate into DNA was less than that of araT monophosphate, and both analogues were retained in DNA for > or =48 h. Thus, the superior cytotoxicity of ganciclovir was not due to enhanced metabolism to active forms. Highly cytotoxic concentrations of ganciclovir produced only weak inhibition of DNA synthesis. This allowed cells to proceed through S and G2-M phases during and after drug exposure, resulting in a doubling of cell number by 48 h after drug washout. As they attempted to progress through the cell cycle a second time, ganciclovir-treated cells accumulated in early S-phase and remained there until cell death, suggesting that ganciclovir incorporation in the DNA template was important for cytotoxicity. In contrast, strong inhibition of DNA synthesis by araTTP prevented cells from traversing the cell cycle for at least 12 h after drug washout, when the active metabolite was largely degraded araT-treated cells were unable to divide for at least 72 h after drug exposure, at which point the surviving cells displayed a normal cell cycle distribution pattern. Based on the results presented here, we propose a novel paradigm in which the ability of ganciclovir to incorporate into DNA without inhibiting progression through S-phase, combined with high cytotoxicity for incorporated ganciclovir monophosphate, produces multilog cytotoxicity.
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PMID:Superior cytotoxicity with ganciclovir compared with acyclovir and 1-beta-D-arabinofuranosylthymine in herpes simplex virus-thymidine kinase-expressing cells: a novel paradigm for cell killing. 973 97

Despite extensive surgery for glioblastoma, residual tumor cells always lead to relapse. Gene therapy based on retrovirus-mediated gene transfer of herpes simplex virus type 1 thymidine kinase (HSV-1 TK), which specifically sensitizes dividing cells to ganciclovir (GCV) toxicity, may help eradicate such cells. During glioblastoma surgery, HSV-1 TK retroviral vector-producing cells (M11) were injected into the surgical cavity margins after tumor debulking. After a 7-day transduction period, GCV was administered for 14 days. Safety was assessed by clinical and laboratory evaluations, and efficacy was assessed by MRI-based relapse-free survival at month 4 and by overall survival. Twelve patients with recurrent glioblastoma were treated without serious adverse events related to M11 cell administration or GCV. Quality of life was not negatively influenced by this treatment. Overall median survival was 206 days, with 25% of the patients surviving longer than 12 months. At 4 months after treatment, 4 of 12 patients had no recurrence; their median overall survival was 528 days, compared with 194 days for patients with recurrence (p=0.03 by the log rank test). One patient is still free of detectable recurrence, steroid free and independent, 2.8 years after treatment. Thus, brain injections of M11 retroviral vector-producing cells for glioblastoma HSV-1 TK gene therapy were well tolerated and associated with significant therapeutic responses. These results warrant further development of this therapeutic strategy in brain tumor, including recurrent glioblastoma.
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PMID:A phase I/II study of herpes simplex virus type 1 thymidine kinase "suicide" gene therapy for recurrent glioblastoma. Study Group on Gene Therapy for Glioblastoma. 985 26

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

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 through the transfer of phosphorylated GCV, there is little direct proof that bystander cells can accumulate GCV nucleotides. We have studied the ability of U251 human glioblastoma cells expressing HSV-TK (U251tk cells) to induce cytotoxicity in neighboring U251 bystander cells that lack the viral kinase (U251beta gal cells) and evaluated whether this bystander cell killing is mediated by GCV nucleotides. The cytotoxicity studies demonstrated that the ratio of HSV-TK-expressing cells:bystander cells was important in determining the sensitivity of both cell types to GCV. U251tk cells cocultured with an equal number of U251beta gal cells (a 50:50 ratio) exhibited a sensitivity to GCV similar to that observed in the absence of bystander cells, with >99.8% cell kill at 1 microm GCV. However, in cultures with 10% U251tk cells and 90% bystander cells (a 10:90 ratio), 1 microM GCV decreased the survival of U251tk cells by only 54%. Strong bystander cell killing was observed at both ratios. In a 50:50 coculture of U251tk and U251beta gal cells, the survival of bystander cells was decreased by >99.5% with 3 microM GCV, whereas 30 microM GCV was required to effect a similar decrease in bystander cell survival when 90% of the culture consisted of U251beta gal cells. To determine whether this bystander cell killing may be mediated by GCV nucleotides, we developed a technique to separate the two cell populations after coculture. A U251 bystander cell line was developed from the parental cell line by transfection with the cDNA coding for green fluorescent protein (U251gfp cells), which permitted the separation of U251gfp cells from nonfluorescing U251tk cells by flow cytometry with cell sorting. With this technique, bystander cells were isolated in a viable state with >97% purity within 1 h after harvest, permitting analysis of the nucleotide pools for the presence of phosphorylated GCV. The results demonstrated that significant levels of the triphosphate of GCV (GCVTP) accumulated in bystander cells within 4 h of coculture, and this accumulation was dependent upon the percentage of HSV-TK-expressing cells as well as the concentration of GCV and the length of incubation. The proportion of GCVTP in bystander cells was consistently 50-80% of that in HSV-TK-expressing cells in the 50:50 or 10:90 cocultures, suggesting a facile transfer of phosphorylated GCV. However, the actual amount of GCVTP was as much as 8-fold lower in both the U251tk and U251beta gal cells cocultured at a ratio of 10:90 compared to those cocultured at a ratio of 50:50, which is consistent with the lesser effect on cell survival. When U251tk and U251gfp cells were cultured with 1-beta-D-arabinofuranosylthymine (araT), the 5'-triphosphate of araT accumulated in the bystander cells, demonstrating that the transfer of phosphorylated compounds between these cell types is not restricted to GCV nucleotides. However, the proportion of araT-5'-triphosphate in bystander cells compared to that in HSV-TK-expressing cells was lower than that for GCVTP, and the amount was not sufficient to decrease survival in the bystander population.
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PMID:Cytotoxicity and accumulation of ganciclovir triphosphate in bystander cells cocultured with herpes simplex virus type 1 thymidine kinase-expressing human glioblastoma cells. 997 16


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