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:3.5.4.1 (cytosine deaminase)
747 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antitumor effects of combined transfer of suicide and cytokine genes were investigated in this study. Adenovirus harboring E. coli cytosine deaminase gene (AdCD) and adenovirus harboring murine granulocyte-macrophage colony-stimulating factor gene (AdGMCSF) were used simultaneously for in vivo gene transfer in melanoma-bearing mice. Growth inhibition of established tumors and prolongation of survival period were observed more significantly in tumor-bearing mice after transfection with AdGMCSF and AdCD followed by continuous injection of prodrug 5-fluorocytosine (5FC) when compared with mice treated with control adenovirus AdlacZ/5FC, AdCD/5FC or AdGMCSF alone (P < 0.01). After combined therapy the expression of MHC-I (H-2Db) and B7-1 molecules on freshly isolated tumor cells increased greatly and more dendritic cells and CD8+ T cells infiltrated into the tumor mass. The activity of specific cytotoxic T lymphocytes was also found to be induced more significantly after the combined therapy. Further experiments showed that apoptosis of tumor cells and induction of antitumor immune response might be involved in the mechanisms of the tumor cell killing by the combined therapy. Our results demonstrated that combined transfer of the GM-CSF and CD suicide genes, being able to inhibit the growth of melanoma synergistically and induce specific antitumor immune response efficiently, thus addressing the drawbacks of suicide gene therapy or cytokine gene therapy which were proved to be not satisfactory when used alone, might be of therapeutic potential for gene therapy of cancer.
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PMID:Adenovirus-mediated GM-CSF gene and cytosine deaminase gene transfer followed by 5-fluorocytosine administration elicit more potent antitumor response in tumor-bearing mice. 1032 37

We constructed a series of adenoviral (Ad) vectors that express the Candida albicans cytosine deaminase (CD) suicide gene under the transcriptional control of either the human alpha-lactalbumin (ALA) or ovine beta-lactoglobulin (BLG) promoter (Ad.ALA.CD and Ad.BLG.CD, respectively). The Ad.ALA.CD and the Ad.BLG.CD vectors converted the prodrug 5-fluorocytosine (5-FC) to the toxic nucleotide analog 5-fluorouracil in a breast cancer cell-specific manner, with a conversion rate of 40% and 52% in T47D cells and 50% and 41% in MCF7 cells, respectively. No significant conversion (< or =3%) was observed in an immortalized nontumorigenic breast epithelial cell line (MCF10A) and a human osteosarcoma cell line (U2OS). Adenovirus vector-based prodrug conversion of the 5-FC in T47D and MCF7 in the presence of 1 mg/mL of 5-FC led to cytotoxicity that resulted in a nearly complete cell death (> or =90%) after 5 days, whereas MCF10A and U2OS cells remained resistant (< or =10%). Nude mice harboring T47D-derived breast tumors that were injected intratumorally (i.t.) with therapeutic adenovirus vectors at a dose of 2 x 10(8) plaque-forming units and treated systemically with 5-FC at a concentration of 500 mg/kg/day showed a marked reduction in tumor mass within 30 days when compared with animals that received vector alone. Animal survival was significantly prolonged after 72 days in mice treated with therapeutic vectors in conjunction with prodrug when compared with control animals. These preclinical data are sufficiently promising to warrant further studies of this transcriptional targeting approach to breast cancer treatment.
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PMID:Breast cancer-specific expression of the Candida albicans cytosine deaminase gene using a transcriptional targeting approach. 1088 14

Utilization of molecular biology techniques offers attractive options in nuclear medicine for improving cancer imaging and therapy with radiolabeled peptides. Two of these options include utilization of phage-panning to identify novel tumor-specific peptides or single chain antibodies and gene transfer techniques to increase the number of antigen/receptor sites expressed on malignant cells. Our group has focused on the latter approach for improving radiolabeled peptide imaging and therapy. The most widely used gene transfer vectors in clinical gene therapy trials include retrovirus, cationic lipids, and adenovirus. We have utilized adenovirus vectors for gene transfer because of their ability to accomplish efficient in vivo gene transfer. Adenovirus vectors encoding the genes for a variety of antigens/receptors (carcinoembryonic antigen, gastrin-releasing peptide receptor, somatostatin receptor subtype 2 (SSTr2)) have all shown that their expression is increased on cancer cells both in vitro and in vivo following adenovirus infection. Of particular interest has been the adenovirus encoding for SSTr2 (AdCMVSSTr2). Various radioisotopes have been attached to somatostatin analogues for imaging and therapy of SSTr2-positive tumors both clinically and in animal models. The use of these analogues in combination with AdCMVSSTr2 is a promising approach for improving the detection sensitivity and therapeutic efficacy of these radiolabeled peptides against solid tumors. In addition, we have proposed the use of SSTr2 as a marker for imaging the expression of another cancer therapeutic transgene (e.g. cytosine deaminase, thymidine kinase) encoded within the same vector. This would allow for non-invasive monitoring of gene delivery to tumor sites.
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PMID:Gene transfer strategies for improving radiolabeled peptide imaging and therapy. 1110 86

Adenovirus (Ad)-mediated gene transfer to the respiratory epithelium of experimental animals and to nasal and airway epithelium of individuals with cystic fibrosis is followed by transient gene expression. Extensive studies in experimental animals are consistent with the concept that local cellular host anti-vector immune responses account for this short-term expression, and systemic and local [lung epithelial lining fluid (ELF)] anti-Ad neutralizing antibodies are generated following Ad vector administration to the respiratory epithelial surface. To determine if this paradigm holds in normal humans, a first-generation Ad vector (Ad(GV)CD.10, an E1(-)E3(-) Ad serotype 5-based vector coding for the Escherichia coli cytosine deaminase gene) was sprayed locally in escalating doses (8 x 10(8)-8 x 10(10) particle units (pu), n = 2/group) into the lung airway epithelium of six normal individuals. Serum, ELF, and endobronchial biopsies were obtained at baseline and at various time points following vector administration. In contrast to the observations in experimental animals in which lung administration of first-generation Ad vectors is followed by strong systemic and local host response, bronchial spray administration of the Ad vector to normal humans showed: (1) minimal inflammation in bronchial biopsies, bronchial brushing, and bronchoalveolar lavage fluid; (2) no blood lymphocyte proliferation in five of six individuals in response to in vitro stimulation with Ad antigens; and (3) no significant increase from baseline in blood or lung ELF anti-Ad neutralizing antibodies. Despite this minimal normal human anti-Ad host response, dose-dependent levels of vector DNA in the airway epithelium were transient. Vector DNA in the targeted airway epithelial cells peaked in a dose-dependent fashion at 0.007 to 1.1 copies/cell at day 7 and declined thereafter, reducing to <10% of peak levels by 2 weeks. These observations demonstrate both the strengths and the limits of using experimental animals to predict human responses to gene transfer vectors. While the transient nature of Ad vector persistence in the airway epithelium is predicted by most experimental animal studies, respiratory epithelial administration of first-generation Ad vectors at doses up to 10(10) pu to airway epithelium of healthy individuals elicits minimal to no detectable systemic and mucosal humoral and cellular immune responses, an observation diametrically opposed to the host responses measured in experimental animals. These findings suggest that, while adaptive anti-Ad immune responses likely play some role in the disappearance of the vector DNA following vector administration to the human lung, other mechanisms may also be involved in the response of humans to Ad gene transfer vectors.
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PMID:Host responses and persistence of vector genome following intrabronchial administration of an E1(-)E3(-) adenovirus gene transfer vector to normal individuals. 1123 77

Tumor-specific gene delivery is crucial to achieving successful effects in suicide gene therapy. Carcinoembryonic antigen (CEA) promoter has been widely used for this purpose, but the expression level of tumor-specific promoters such as CEA promoter is generally low. In the previous study, we used the Cre/loxP system and showed that LacZ expression by the CEA promoter was remarkably enhanced and maintained its specificity using the Cre/loxP regulation system. In this study, the Cre/loxP system was first applied to augmentation of selective expression of the cytosine deaminase (CD) gene as a suicide gene therapy in CEA-producing cells. The double infection with AxCEANCre expressing Cre recombinase under the control of the CEA promoter and AxCALNLCD expressing the CD gene under the control of the CAG promoter by the Cre switching system rendered CEA-producing tumor cells 13-fold more sensitive to 5-fluorocytosine (5-FC) compared with the single infection with AxCEACD expressing CD gene driven by the CEA promoter. The therapeutic efficacy of the enhanced CD/5-FC suicide gene therapy was evaluated in orthotopic implantation models of human gastric carcinoma. Adenovirus vectors (1 x 10(9) plaque-forming units) were administered i.p. into mice three times, and then 5-FC was administered i.p. for the next 10 days. Tumor volume and weight in mice treated with AxCEANCre and AxCALNLCD/5-FC were significantly reduced as compared with those in mice treated not only with Mock (AxCALacZ) but also with AxCEACD/5-FC (P < 0.0001). This beneficial effect on tumor burden was also reflected in the overall survival. The survival periods of the mice treated with AxCEANCre and AxCALNLCD/5-FC were longer than those of mice treated with Mock or AxCEACD/5-FC (P < 0.01). These results suggested that application of the Cre/loxP system could provide a new approach for enhanced selective suicide gene therapy of CD/5-FC for the treatment of advanced gastric carcinoma.
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PMID:Carcinoembryonic antigen-specific suicide gene therapy of cytosine deaminase/5-fluorocytosine enhanced by the cre/loxP system in the orthotopic gastric carcinoma model. 1150 67

Adenovirus (Ad) gene transfer vectors traffic to regional lymph nodes (RLNs) after footpad injections in mice, resulting in localized production of interferon gamma (IFN-gamma). With this background, we evaluated the hypothesis that Ad vector administration may inhibit RLN tumor metastasis independent of the transgene in the expression cassette. Tumors of MM48, a cell line with a propensity toward lymphogenous metastasis, were established in the footpads of syngeneic C3H mice, and E1(-)E3(-) Ad vectors encoding no transgene (AdNull) or encoding an irrelevant transgene (AdCD; Escherichia coli cytosine deaminase with no 5-fluorocytosine administration) were administered (10(10) particles) in a peritumoral location. Both vectors suppressed the growth of tumor in the regional (popliteal) lymph node. This effect was localized to the regional, but not distant, lymph nodes (p < 0.05). Heat inactivation of the vector or decreasing the dose of the vector to 10(9) particles did not suppress RLN growth of the tumor when compared with 10(10) particles of active AdNull (p < 0.05 and p < 0.01, respectively). The ability of an E1(-)E4(-) vector expressing beta-galactosidase (AdRSVbetagal.11) to suppress RLN tumor growth showed that the E4 region of the Ad vector was not responsible for the effect. Blocking either IFN-gamma or natural killer (NK) cells with systemic antibody treatment in immunocompetent mice allowed rapid growth of RLN metastases despite Ad vector administration, and Ad vector injection into the footpads of tumor-free mice induced the accumulation of NK cells in the RLN. These data demonstrate that, in a metastatic murine tumor model, a low dose (10(10) particles) of replication-deficient Ad vectors inhibits RLN metastases independent of a therapeutic transgene, an effect that is mediated, at least in part, by IFN-gamma and NK cells.
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PMID:Adenovirus gene transfer vectors inhibit growth of lymphatic tumor metastases independent of a therapeutic transgene. 1153 67

5-Fluorouracil (5-FU) is a potent antimetabolite used for chemotherapy of gastrointestinal (GI), breast, and head and neck malignancies. Although clinical trials have been conducted, the poor therapeutic index of 5-FU has precluded its clinical use for a number of other tumor types. It is unclear whether this lack of utility is due to problems with drug delivery or inherent insensitivity. Adenovirus (Ad) vector-mediated cytosine deaminase (CD)/5-fluorocytosine (5-FC) gene therapy has the potential to overcome pharmacokinetic issues associated with systemic 5-FU and is particularly well suited to use with tumors in which local control is paramount, such as recurrent, localized prostate cancer and malignant gliomas. In this study, the in vitro response by a panel of human tumor cell lines derived from both GI (colon, pancreas) and non-GI (prostate, glioma) tumors to 5-FU and to AdCMVCD (an Ad encoding Escherichia coli CD)/5-FC was examined. Whereas the sensitivity (IC(50)) of individual cell lines to these agents varied, no significant difference in median IC(50) for either 5-FU or AdCMVCD/5-FC was evident for the four tumor types tested (P > 0.1). The relevant contributions of Ad gene transfer efficiency and inherent 5-FU sensitivity in determining response to AdCMVCD/5-FC were then assessed. Multiple linear regression analysis revealed that whereas both factors significantly contribute to the response, inherent 5-FU sensitivity was substantially more important (beta= 0.78 versus 0.48; P < 0.001). Finally, the therapeutic efficacy of a single intratumoral injection of AdCMVCD followed by systemic 5-FC was assessed in three intracranial C.B17 severe combined immunodeficient mouse models of human glioma. AdCMVCD/5-FC efficacy was specific, virus dose-dependent, and closely paralleled in vitro 5-FU and CD/5-FC sensitivity in two of three models tested. These results reveal that glioma cells are as sensitive as GI tumor cells to the antineoplastic effects of 5-FU, identify inherent 5-FU sensitivity as an important factor in determining CD/5-FC efficacy, and confirm previous findings in rat models that demonstrate the potential clinical utility of AdCMVCD/5-FC gene therapy for gliomas.
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PMID:Intratumoral 5-fluorouracil produced by cytosine deaminase/5-fluorocytosine gene therapy is effective for experimental human glioblastomas. 1183 May 32

Adenovirus-mediated suicide gene therapy may hold promise in the treatment of human cancer. We have developed a novel approach that utilizes a lytic, replication-competent adenovirus (Ad5-CD/TKrep) to deliver a cytosine deaminase/herpes simplex virus-1 thymidine kinase fusion gene to tumors. The cytosine deaminase and herpes simplex virus-1 thymidine kinase suicide genes render malignant cells sensitive to specific pharmacological agents and, importantly, sensitize them to radiation. The Phase I study described here represents the first gene therapy trial in which a replication-competent virus was used to deliver a therapeutic gene to humans. The indication is local recurrence of prostate cancer after definitive radiation therapy. An escalating dose (10(10), 10(11), and 10(12) viral particles) of the Ad5-CD/TKrep virus was injected intraprostatically under transrectal ultrasound guidance into 16 patients in four cohorts. Two days later, patients were given 5-fluorocytosine and ganciclovir prodrug therapy for 1 (cohorts 1-3) or 2 (cohort 4) weeks. There were no dose-limiting toxicities, and the maximum tolerated dose of the Ad5-CD/TKrep vector was not defined. Ninety-four percent of the adverse events observed were mild or moderate (grade 1/2) in nature. Seven of 16 (44%) patients demonstrated a >or=25% decrease in serum prostate-specific antigen, and 3 of 16 (19%) patients demonstrated a >or=50% decrease in serum prostate-specific antigen. Transgene expression and tumor destruction at the injection site were confirmed by sextant needle biopsy of the prostate at 2 weeks. Two patients were negative for adenocarcinoma at 1 year follow-up. Although Ad5-CD/TKrep viral DNA could be detected in blood as far out as day 76, no infectious adenovirus was detected in patient serum or urine. Together, the results demonstrate that intraprostatic administration of the replication-competent Ad5-CD/TKrep virus followed by 2 weeks of 5-fluorocytosine and ganciclovir prodrug therapy can be safely applied to humans and is showing signs of biological activity.
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PMID:Phase I study of replication-competent adenovirus-mediated double suicide gene therapy for the treatment of locally recurrent prostate cancer. 1220 48

A major potential limitation to the success of enzyme prodrug gene therapy is the toxicity that could result from gene expression in normal tissues. In this study, we investigated the use of an enhanced human carcinoembryonic antigen (CEA) promoter for yeast cytosine deaminase (yCD), which converts 5-fluorocytosine to 5-fluorouracil, to increase targeting while maintaining activity both in cell culture and in nude rats bearing intrahepatic xenografts. We found that an enhanced CEA-yCD adenoviral vector can achieve significantly greater yCD expression in CEA-expressing colon carcinoma cell lines (LoVo, HT29, and CaCo2) compared with a nonspecific Rous sarcoma virus-yCD virus. In contrast, infection with CEA-yCD led to lower or equivalent yCD expression in normal hepatocytes or fibroblasts compared with that produced by the RSV-yCD. Adenovirus administered in the portal vein or the hepatic artery of nude rats bearing intrahepatic LoVo colon carcinomas could mediate beta-galactosidase expression equally in liver and tumors under the control of cytomegalovirus, a nonspecific promoter. However, infusion of CEA-yCD virus markedly increased yCD expression in tumors over normal liver (>4-fold) measured both by levels of mRNA and yCD activity. Moreover, the efficiency of 5-fluorocytosine conversion into 5-fluorouracil in tumors was significantly higher than that in normal liver ( approximately 3-fold) in rats receiving portal venous viral infusion of CEA-yCD and subsequent 5FC treatment. Thus, an enhanced CEA promoter can preferentially stimulate yCD gene expression in CEA-expressing cells in vivo. Such tumor-specific expression should prove useful in colorectal cancer gene therapy to achieve selective prodrug conversion in tumors.
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PMID:Regional delivery and selective expression of a high-activity yeast cytosine deaminase in an intrahepatic colon cancer model. 1256 11

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