Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.4.1 (cytosine deaminase)
 747 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Yeast cytosine deaminase (yCD)-based gene therapy offers the potential for selective production of the cytotoxic and radiosensitizing drug 5-fluorouracil (5-FU) from the benign prodrug 5-fluorocytosine within colorectal cancers. Although previous attempts to target therapy to colorectal cancer using the carcinoembryonic antigen (CEA) promoter have demonstrated specificity, this has been achieved at the cost of 10- to 300-fold loss in activity compared with strong but nonspecific rous sarcoma virus (RSV) or cytomegalovirus promoters. We developed a highly specific and active gene transfer method for colorectal cancer using CEA under control of a promoter-enhancer. We compared the RSV promoter-derived with the CEA promoter-enhancer-derived transgene expression in 10 different cell lines with differing CEA status. We found that the transgene expression resulting from both transient transfection and adenoviral infection with the CEA promoter-enhancer was as strong as the RSV promoter while maintaining specificity for CEA-producing cell lines. For instance, when we compared yCD expression between LoVo (CEA+) and human fibroblast (CEA-), we found a 30-fold-increased yCD expression in LoVo cells from CEA-enhancer adenovirus although there was no difference in the yCD expression between the cell lines when infected with RSV/yCD virus. This specificity was also achieved while maintaining a higher yCD enzyme activity than we obtained with RSV/yCD adenovirus in an HT-29 intrahepatic tumor model. We then compared the response of HT-29 xenografts to treatment with 5-fluorocytosine and yCD adenovirus driven by either the RSV or the CEA promoter-enhancer and found similar tumor growth inhibition. These findings suggest that the CEA promoter-enhancer strategy confers specificity while preserving activity and is worth exploring in additional animal and, potentially, clinical trials.
Cancer Res 2002 Apr 15
PMID:High and selective expression of yeast cytosine deaminase under a carcinoembryonic antigen promoter-enhancer. 1195 93

The cytosine deaminase (CD) gene converts the nontoxic prodrug, 5-fluorocytosine (5-FC), into 5-fluorouracil (5-FU). We previously showed that injection of CD-bearing cancer cells followed by 5-FC treatment can act as an autologous tumor vaccine in a syngenic liver metastasis model in rats. In the present work, we analyzed the antitumor efficiency of a direct intratumoral injection of a CD-expressing plasmid. In rats bearing microscopic or macroscopic metastases in right and left liver lobes, an injection of a CD-expressing plasmid was performed in the left lobe tumor, followed by 5-FC treatment of the animals. A significant regression of the DNA-injected tumor was observed in 5-FC-treated rats, both in microscopic (P =.007) or advanced (P <.0001) tumor models. Moreover, this treatment also induced a potent distant bystander effect on untreated controlateral liver tumors and extrahepatic metastases, resulting in an increased survival compared with control animals in both tumor models (P <.05). In conclusion, these data suggest that direct intratumoral injection of a CD-expressing plasmid, associated to 5-FC administration, can constitute a powerful and innocuous alternative treatment for unresectable liver metastases from colon carcinoma.
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PMID:Naked DNA injection for liver metastases treatment in rats. 1198 64

To study the possibility of oral gene therapy using live attenuated Salmonella, eukaryotic expression vectors EGFPN1, pLCDSN were introduced into a live attenuated AraA(-) auxotrophic mutant of Salmonella typhimurium (SL3261) and were administered orally to BALB/c and C57BL/6 mice. After six weeks, these mice were challenged with 4T(1) and Lewis cancer cells. Until the tumors reached to about 10 mm in diameter, 5-fluorocytosine was given through intraperitoneal injection. Flow cytometry, confocal microscopy and PCR methods were used to detect the integration and expression of the genes. The inhibition of the tumor and the survival time of the mice were also investigated. Results showed that cytosine deaminase gene integration could be detected in almost all kinds of mice tissue. And the GFP expression was much stronger in spleen and tumor than in other tissues. Cytosine deaminase/5-fluorocytosine system had significant antitumoractivities in vivo. The anti-tumor activities of cytosine deaminase/5-fluorocytosine at 500 mg/kg on 4T(1) and Lewis carcinoma in BALB/c and C57BL/6 mice were more potent than the efficiency of 5-fluorouracil 10 mg/kg(P 0.05). Therefor, this experiment demonstrates the potential value of live attenuated Salmonella as carrier for oral gene therapy.
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PMID:Treatment of Tumor in Mice by Oral Administration of Cytosine Deaminase Gene Carried in Live Attenuated Salmonella. 1205 Aug 17

Using a syngeneic murine model, we investigated the therapeutic efficacy of combined gene therapy using adenoviral vectors expressing murine interleukin-2 (AdmIL-2) and Escherichia coli cytosine deaminase (AdCD). In a subcutaneous tumor model, tumor-bearing mice were treated with an intratumoral injection of adenoviral vectors and received an intraperitoneal administration of 5-fluorocytosine (5-FC). Only the mice treated with AdCD (2 x 10(8) pfu) and an intermediate dose of AdmIL-2 (1 x 10(6) pfu) survived significantly longer than mice treated with AdCD alone (P < 0.01). Moreover, 40% of these treated mice obtained complete remission from tumor-bearing status. The cytotoxicity of splenocytes obtained from the treated mice was related to the survival period. Tumor-specific cytotoxic T lymphocyte assay showed that the cell-mediated cytotoxic response was specific for parental tumor cells. In a hepatic metastasis model, mice treated with an intravenous administration of both AdCD (2 x 10(8) pfu) and an intermediate dose of AdmIL-2 (1 x 10(6) pfu) demonstrated the most significant reduction of metastatic foci and the longest survival following a 5-FC administration. These results suggest that gene therapy combined with AdmIL-2 and AdCD may be a promising strategy for clinical application and, in addition, that translation of combined gene therapy from murine models into the clinical setting will require careful attention to the variables of cytokine expression levels in the design of clinical trials and in the evaluation of treatment efficacy.
Jpn J Cancer Res 2002 Jun
PMID:Dose of adenoviral vectors expressing interleukin-2 plays an important role in combined gene therapy with cytosine deaminase/5-fluorocytosine: preclinical consideration. 1207 20

Colorectal cancer can metastasize to the liver, but remain liver confined for years. A critical step in developing treatments for intrahepatic cancer involves assessment in an orthotopic intrahepatic model. The purpose of this study was to develop a noninvasive intrahepatic tumor model to study the efficacy of 5-flucytosine/yeast cytosine deaminase (5FC/yCD)-based gene therapy for liver tumors. Luciferase expressing human colorectal carcinoma (HT-29luc) cells were generated by retroviral infection and implanted in the left liver lobe of nude mice. The bioluminescence was measured every week for a period of 1 month, then animals were killed and tumors were measured by calipers. After we found a correlation between photon counts and tumor size, animals were implanted with tumors composed of either 0%, 10%, or 100% yCD/HT-29luc cells, and treated with 5FC. Tumor bioluminescence was measured during treatment and tumor histology examined at the time of death. We found that 5FC caused significant regression of yCD expressing tumors. Furthermore, visible tumors at the time of death, which emitted little bioluminescence, contained little or no viable tumor. We then developed an adenoviral vector for yCD. Intraperitoneal administration of adenovirus containing yCD led to the production of yCD enzyme within intrahepatic tumors. These results suggest that (1) intrahepatic cancer responds to 5FC when cells express yCD; (2) the luciferin-luciferase system permits non-invasive real time imaging of viable intrahepatic cancer; and (3) this system can be used to carry out gene therapy experiments using yCD adenovirus.
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PMID:The potential of 5-fluorocytosine/cytosine deaminase enzyme prodrug gene therapy in an intrahepatic colon cancer model. 1208 Mar 78

The feasibility of gene therapy strategies in cancer treatment still has important pitfalls. Transfer of therapeutic proteins to the hypoxic/necrotic 'extracellular' microenvironment of solid tumors, based on the engineering of nonpathogenic clostridia is proposed as an alternative methodology. Using the rat rhabdomyosarcoma R1 in vivo tumor model, we demonstrated that Clostridium species colonized the tumors, whereas proliferation of these bacteria was absent in normal tissues. C. acetobutylicum was genetically engineered to express and secrete either mTNF-alpha or the E. coli cytosine deaminase. Quantitative in vitro data showed stability of the vectors, and significant levels of biologically active therapeutic proteins in lysates and supernatants of recombinant clostridia. Administration of either of these recombinant Clostridium strains to tumor-bearing rats resulted in the presence of active proteins in the tumor tissue. Based on these data and supported by its selective colonization pattern and safety, the Clostridium gene transfer system offers a potential application in anti-cancer therapies.
Cancer Detect Prev 2001
PMID:Clostridium as a tumor-specific delivery system of therapeutic proteins. 1213 75

Human telomerase reverse transcriptase (hTERT), the catalytic subunit of the telomerase, is transcriptionally upregulated in more than 90% of tumor cells. It may be used as a tool for driving a gene to kill tumors specifically. To test this idea, luciferase reporter gene was used and the results showed that hTERT promoter could restrict the gene expression in the telomerase-positive tumor cells. A tumor-specific expression plasmid phTERT-CD was constructed, in which the E. coli cytosine deaminase (CD) gene was controlled by the hTERT promoter. A colorectal cancer cell line (LoVo) and a normal amnion cell line (WISH) were transfected by this plasmid. It was shown that the expression of the CD gene increased the sensitivity of LoVo cells to the prodrug, 5-fluorocytosine (5FC), over 800-fold, while the sensitivity of WISH cells to 5FC was increased only 6-fold. Mixed cell experiments showed a strong "bystander effect" on CD-negative cells. Furthermore, a significant anti-tumor effect of the phTERT-CD/5FC system was observed in nude mice bearing mammalian carcinoma induced by s.c. inoculation of LoVo cells when the mice were given 250 mg/kg 5FC twice a day for 10 consecutive days. These results indicated that hTERT promoter could target the suicidal effect of CD gene to tumor cells, and therefore, may be a novel and promising targeting approach to the treatment of cancer.
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PMID:Cancer-specific killing by the CD suicide gene using the human telomerase reverse transcriptase promoter. 1216 15

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.
Cancer Res 2002 Sep 01
PMID:Phase I study of replication-competent adenovirus-mediated double suicide gene therapy for the treatment of locally recurrent prostate cancer. 1220 48

Tumor cell contamination of clinical grafts is a major concern in autologous hematopoietic stem cell transplantation because these contaminating cells can contribute to relapse. In the present work, we use a suicide gene therapy approach that successfully accomplishes the two main goals of any purging strategy: highly efficient elimination of contaminating tumor cells and preservation of the engraftment capability of the hematopoietic progenitor cells. Human CD34(+) cells spiked with breast cancer cells were infected with an adenoviral vector encoding the cytosine deaminase transgene (Ad-CMV-CD). In vitro, transduction with Ad-CMV-CD followed by exposure to 400 micro M 5-fluorocytosine resulted in complete elimination of clonogenic contaminating tumor cells without affecting the clonogenic potential of the human hematopoietic CD34(+) cells. Transplantation of nonobese diabetic/LtSz-scid/severe combined immunodeficient (NOD/SCID) mice with nonpurged contaminated grafts and purged contaminated grafts, allowed us to test the safety and efficacy of our procedure in two independent purging experiments. Hematopoietic engraftment kinetics as well as the quantity and quality of human engraftment were not affected by the purging therapy. Results showed a significant difference in survival between the nonpurged group (28%) and the purged group (100%; P = 0.012). Moreover, highly sensitive histological and molecular analyses confirmed the absence of tumor cells in the recipients of purged marrow. In contrast, metastatic tumors were detected in animals that received nonpurged grafts. We anticipate that this strategy will result in a safe and efficacious hematopoietic graft product for autologous transplantation for patients with multiple forms of epithelial cancers.
Cancer Res 2002 Sep 01
PMID:Efficient and nontoxic adenoviral purging method for autologous transplantation in breast cancer patients. 1220 55

The recombinant retroviral vector pLCDSN containing E. coli cytosine deaminase gene was constructed. After packaging with PA317 cell line, the infectious particles were used to infect human colon carcinoma cell line LoVo. A single clone harbouring EC-CD gene was picked after G418 selection. There was no significant difference in cell growth curve or morphology between the LoVo/LCDSN and LoVo cells. Both of them were very sensitive to 5-FU in vitro (IC(50), approximately 0.5 &mgr;mol/L). However, the expression of the CD gene did increase the sensitivity of these cells to the nontoxic prodrug, 5-FC, decreasing the IC(50) for 5-FC from 22 000 &mgr;mol/L for parental LoVo cells to 13 &mgr;mol/L for LoVo/LCDSN cells. Obvious by side effect was also observed. When cells transduced with CD gene were mixed with wild type cells at a ratio of 30:70, above 80% of the cancer cells could be killed after treatment with a nontoxic concentration of 5-FC.
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PMID:Expression of Cytosine Deaminase Gene in Human Colon Carcinoma Cells by Recombinant Retroviral Vector. 1221 18


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