Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The bacterial enzyme cytosine deaminase (CD) catalyzes the conversion of 5-fluorocytosine (5-FC) to the lethal 5-fluorouracil (5-FU) and so provides a useful system for selective killing of gene-modified mammalian tumor cells. Cloning of the CD gene from Escherichia coli and expression in human tumor cell lines enabled these cells to convert 3H-labeled 5-FC into 3H-5-FU. Two CD-expressing human tumor cell lines (adenocarcinoma cell line KM12 and glioblastoma cell line T1115) became 200-fold more sensitive to 5-FC than the nonexpressing parental cell lines. At least 90% of the cells are killed within 7 days. CD-expressing cells are able to kill nonexpressing cells when grown in the same culture flask (bystander effect). The CD gene may be used as a suicide system for in situ chemotherapy or as a safety mechanism abrogating the expression of other genes.
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PMID:Cytosine deaminase gene as a potential tool for the genetic therapy of colorectal cancer. 854 59

Transduction of malignant cells with toxin genes provides a novel means to promote tumor cell destruction. The efficacy of a toxin gene is dependent on the cell type targeted, the quantity of exogenous protein synthesized, and the mechanisms of growth inhibition and bystander killing. To develop gene therapy for targeting metastatic lung adenocarcinoma, the toxic activity of herpes simplex virus type 1-thymidine kinase, Escherichia coli cytosine deaminase, and human deoxycytidine kinase were investigated in metastatic human lung adenocarcinoma cell lines H1437 and H2122. Cells were transduced stably with retroviral vectors containing the toxin gene cDNA under the control of either a strong [cytomegalovirus (CMV) immediate early promotor and enhancer] or an intermediate strength (Moloney murine leukemia virus long terminal repeat) promotor. A comparison of toxin gene efficacy was based on the level of specific enzyme activity, the concentration of prodrug required to inhibit cell growth by 50%, and the magnitude of the bystander effect. In lung adenocarcinoma cell lines, cytosine deaminase, driven by the CMV promoter, was superior to thymidine kinase and deoxycytidine kinase in its ability to achieve high levels of specific enzyme activity, to induce growth inhibition, and to affect neighboring cell growth. Therefore, cytosine deaminase expressed from the CMV promotor seems to be the most promising toxin gene for human lung adenocarcinoma gene therapy.
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PMID:Comparison of the effects of three different toxin genes and their levels of expression on cell growth and bystander effect in lung adenocarcinoma. 864 Aug 20

Poorly immunogenic tumor cells genetically transduced to simultaneously express the cytokine interleukin 6 (IL-6) and the bacterial metabolic suicide gene cytosine deaminase (205-IL6-CD) become highly immunogenic. They are rejected by normal mice without 5-fluorocytosine prodrug treatment. Mice with preexisting wild-type pulmonary micrometastases exhibit prolonged survival and an increased rate of cure when treated with live 205-IL6-CD cells as a therapeutic vaccine. Treatment with these autologous tumor cells producing both the cytokine and the bacterial protein was more effective than treatment with exogenous IL-6 and/or irradiated wild-type tumor cells. Irradiation of the 205-IL6-CD cells significantly reduced their therapeutic efficacy. Therapeutic vaccination with 205-IL6-CD was more effective in animals with wild-type 205 tumor than in animals bearing an unrelated syngeneic tumor. Vaccine efficacy was significantly reduced in animals pretreated with high-dose cyclophosphamide. The results indicate that genetically engineered autologous tumor vaccines may be capable of inducing significant antitumor immunity in hosts of preexisting micrometastatic disease.
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PMID:Treatment of microscopic pulmonary metastases with recombinant autologous tumor vaccine expressing interleukin 6 and Escherichia coli cytosine deaminase suicide genes. 864 Aug 26

Our laboratory and others have shown alternative splicing of up to ten exons at a discrete extracellular site to be primarily responsible for the generation of CD44 variant (CD44v) isoforms. Based on clear differences in the expression of these CD44v isoforms between normal and malignant tissues, we believe that elucidation of the mechanisms underlying the regulation of CD44 alternative splicing may provide a new gene therapeutic targeting approach based on CD44 pre-mRNA processing in vivo. This strategy incorporates utilization of CD44 alternative splicing control elements into a chimeric enzyme/prodrug therapy (CEPT), a novel modification of the virus-directed enzyme/prodrug therapy (VDEPT) approach for the treatment of brain metastases from tumors of systemic origin. As initial steps towards the development of a gene therapeutic approach based on targeting tumor cell expression of specific CD44v alternatively spliced isoforms, we have: (1) developed a novel in vivo assay system that allows the rapid analyses of potentially therapeutic CD44 alternative splicing minigene constructs; and (2) cloned the E. coli cytosine deaminase (CD) gene and fused its enzymatically active domain to alternatively spliced CD44 exons (CD44/CD). Deamination of cytosine by this CD44/CD chimeric fusion protein is demonstrated in E. coli cell lysates to be equal to that of wild type cytosine deaminase.
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PMID:Gene therapeutic approach to primary and metastatic brain tumors: I. CD44 variant pre-RNA alternative splicing as a CEPT control element. 875 Jan 90

To target expression of toxic genes to Epstein-Barr virus (EBV)-associated tumor cells, we have developed an EBV-driven enzyme prodrug system (EDEPS) that takes advantage of the trans-activating properties of EBNA1, a latent protein expressed in all EBV-containing cells, to direct expression of cytosine deaminase (CD) at high levels in those cells only. Plasmids were constructed in which the CD gene or a luciferase reporter gene were cloned downstream of the herpes simplex virus thymidine kinase (tk) promoter and the family of repeats (FR) sequence from the oriP region of EBV. Analysis of luciferase activity after transient transfection into a panel of EBV-negative or -positive human cell lines showed that the presence of the FR element enhanced transcription from the tk promoter in all EBV-positive cell lines, whereas transcription from tk was repressed in all EBV-negative cell lines, including B, T, and fibroblast cell lines. In clonogenicity assays following transfection with the CD vector, the presence of 5-fluorocytosine (5-FC) in the culture medium completely abolished cell growth in EBV-positive cell lines, but did not affect the growth of EBV-negative cell lines. This vector system should have wide applicability in that it allows targeted expression of any gene of interest to tumors that carry EBV, irrespective of the role EBV plays in their pathogenesis.
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PMID:Use of Epstein-Barr virus nuclear antigen-1 in targeted therapy of EBV-associated neoplasia. 884 90

To evaluate the hypothesis that regional delivery of an adenovirus vector containing the Escherichia coli cytosine deaminase gene (AdCMV.CD) together with systemic 5-FC could suppress the growth of metastatic colon cancer in the liver, the AdCMV.CD vector was injected 0.8-1 cm from the site of a human colon cancer tumor in the livers of nude mice. The growth of the human colon cancer cells was quantified by dot blot analysis of genomic DNA extracted from tumor-bearing liver, hybridized with a human-specific Alu probe. The combination of regional AdCMV.CD plus systemic 5-fluorocytosine (5-FC) suppressed the growth of the metastatic tumors over the 21 days of evaluation following vector administration. Histologic evaluation showed necrosis at the site of the tumor in the livers of mice treated with AdCMV.CD/5-FC, but not in control groups. Evaluation of the potential toxicity of AdCMV.CD plus 5-FC on the normal liver showed only mild, self-limited dose-related inflammation, with no deaths. These data suggest that the regional administration of AdCMV.CD together with systemic 5-FC may be a safe and effective strategy to suppress the growth of metastases of colorectal carcinoma in the liver.
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PMID:Regional delivery of an adenovirus vector containing the Escherichia coli cytosine deaminase gene to provide local activation of 5-fluorocytosine to suppress the growth of colon carcinoma metastatic to liver. 886 57

An attempt was made to use simple cationic liposomes DC-Chol/DOPE and DDAB/DOPE (DC-Chol is 3 beta (N(N',N-dimethylaminoethane) carbamoyl) cholesterol, DDAB is dimethyldioctadecyl ammonium bromide and DOPE is dioleoylphosphatidylethanolamine) for transfer of Escherichia coli cytosine deaminase 'suicide' gene under the control of tissue-specific tyrosinase gene promoter directly into the murine melanoma B16(F10) tumor. Several repeated intratumoral injections of DNA-liposome complexes followed by intraperitoneal administrations of 5-fluorocytosine, which is converted to 5-fluorouracil, caused strong retardation of murine melanoma B16(F10) tumor growth and, in some cases, rejection of the pre-established tumor. The inhibition of tumor growth expressed as the increased survival of mice is better seen in the case of using DNA-DDAB/DOPE complexes as compared to DNA-DC-Chol/DOPE ones. It seems that the observed therapeutic effect appears to result from several factors: 5-fluorouracil generation by transfected cells, liposome toxicity (DDAB is more toxic than DC-Chol and hence more tumor cells are killed), increased transfection efficiency of surviving cancer cells (in this case DDAB is a better transfection agent than DC-Chol) and, finally, the bystander effect which causes destruction of cells untransfected with CD gene by easily diffusible 5-fluorouracil.
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PMID:The use of cationic liposomes DC-CHOL/DOPE and DDAB/DOPE for direct transfer of Escherichia coli cytosine deaminase gene into growing melanoma tumors. 904 44

To investigate the potential use of E. coli cytosine deaminase (CD) gene instead of the commonly used HSV-TK gene in the gene therapy of brain tumors, we constructed a retrovirus vector carrying the CD gene. We then transduced a rat glioma cell line C6 with CD gene by the retrovirus vector. Transduction of the CD gene made C6 cells become highly sensitive to the anti-fungi drug 5-fluorocytosine (5FC). IC50 for 5FC was 6,000 microM in CD-negative cells, while it was 3 microM in CD-positive cells. Mixed cellular assay showed that CD-positive cells had a strong "bystander effect" on CD-negative cells when exposed to 5FC. Significant anti-tumor effects were observed in nude mice bearing s.c. tumors derived from CD-positive cells when these animals were given 250 mg/kg 5FC twice a day for 20 consecutive days. A marked decrease in tumor weight occurred when a mixture containing 50% CD-positive and 50% CD-negative C6 cells was injected s.c., followed by 5FC treatment, suggesting the bystander effect in vivo. Concerning the pharmacokinetics of 5FC, especially its high oral bio-availability and good penetration into cerebrospinal fluid, we suppose that the combination of CD-gene transfer and 5FC oral administration may have potential use in the gene therapy of brain tumors.
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PMID:Transduction of cytosine deaminase gene makes rat glioma cells highly sensitive to 5-fluorocytosine. 917 25

We report that in vitro 5-fluorocytosine sensitizes B16(F10) melanoma cells to radiation damage when they are transfected with cytosine deaminase gene (CD). The greatest enhancement of radiation cytotoxicity was observed when B16(F10)/CD cells were incubated in medium with 500 microM 5-fluorocytosine for 3 hours, with incubation starting 1 hour after irradiation. 5-Fluorocytosine did not change radiosensitivity of parental, nontransfected cells. The isoeffective dose for CD-transfected cells treated with 5-fluorocytosine was reduced by 20% at a 2-Gy level of effect for nontransfected cells. We believe that the observed outcome is related to 5-fluorouracil generated by CD and subsequent 5-fluorouracil anabolites. Our results support the development of in vivo models for tumor radiosensitization using the CD gene/5-fluorocytosine system.
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PMID:Selective augmentation of radiation effects by 5-fluorocytosine on murine B16(F10) melanoma cells transfected with cytosine deaminase gene. 925 13

Bacterial cytosine deaminase (CD) converts the non-toxic prodrug 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU), which is toxic for mammalian cells. Therefore, the CD gene is used in cancer gene therapy to achieve high local concentration of a toxic metabolite without significant systemic toxicity. To allow the detection of CD expression at the protein level, we raised both polyclonal rabbit antisera and a monoclonal antibody (mAb) against a histidine-tagged CD fusion protein. The specificity of the polyclonal antisera and the mAb was confirmed by immunohistochemistry, immunoblot analysis, and immunoprecipitation using CD-expressing tumor cell lines. Furthermore, the antibodies can be used for ELISA assays and flow cytometry. Finally, the CD protein could be demonstrated in frozen tissue sections of CD-modified tumors in a rat tumor model using the anti-CD serum. With these antibodies, CD expression can now be monitored throughout in vitro and in vivo gene transfer studies, including clinical protocols relying on the CD suicide gene strategy.
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PMID:Detection of cytosine deaminase in genetically modified tumor cells by specific antibodies. 929 34


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