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)

Direct administration of an adenoviral vector expressing the cytosine deaminase gene (AdCMV.CD) to tumors of colon carcinoma cells, with concomitant systemic administration of 5-fluorocytosine (5FC), results in local production of 5-fluorouracil (5FU) and suppression of tumor growth. Based on the demonstration that in vivo adenovirus-mediated gene transfer to intrahepatic tumors is relatively inefficient compared with in vivo gene transfer to hepatocytes, we developed a 'regional' prodrug strategy using in vivo Ad-mediated CD gene transfer to normal liver, permitting hepatocytes to convert 5FC into 5FU to treat local metastasis effectively in a 'trans' fashion. To show that hepatocytes can generate and export sufficient 5FU to achieve this goal, primary rat hepatocytes were exposed to AdCMV.CD and 5FC. Evaluation of the supernatants by spectrophotometry and by HPLC demonstrated significant conversion of 5FC into 5FU. When supernatants of hepatocytes exposed to AdCMV.CD and 5FC were transferred to cultures of CT26 mouse colon carcinoma cells, the CT26 viability was reduced by 80%. To show that this regional AdCMV.CD/5FC prodrug strategy can suppress tumor growth in vivo, a model of metastatic colon carcinoma was established by injecting CT26 cells into the left lobe of the liver of syngeneic Balb/c mice. The next day, AdCMV.CD was transferred to hepatocytes by intravenous administration, and 5FC treatment was started the following day. Evaluation of tumor growth after 15 days showed marked suppression of tumor growth in AdCMV.CD- and 5FC- treated animals compared to control groups (P < 0.007). We conclude that primary hepatocytes are capable of converting 5FC into 5FU and exporting sufficient amounts of 5FU to the local milieu to suppress the growth of liver metastases of colon carcinoma cells.
 ...
PMID:Regional 'pro-drug' gene therapy: intravenous administration of an adenoviral vector expressing the E. coli cytosine deaminase gene and systemic administration of 5-fluorocytosine suppresses growth of hepatic metastasis of colon carcinoma. 961 75

Suicide gene therapy using the cytosine deaminase (CD) gene and 5-fluorocytosine (5-FC) has shown promising results for the treatment of colon carcinoma cells in vitro. Efficient viral infection and tumor-specific gene delivery is crucial for clinically measurable treatment effects. After proving efficient gene transfer in vitro, we demonstrate here that genes can be delivered to metastatic liver tumors in vivo in a highly selective manner using systemic delivery of a thymidine kinase-deleted (TK-) recombinant vaccinia virus (Western Reserve strain). When the vector was administered systemically in C57BL/6 mice or nude/athymic mice with established disseminated MC38 liver metastases, transgene expression in tumors was usually 1,000 to 10,000-fold higher compared with other organs (n = 160; P < 0.0001). This tumor-specific gene transfer leads to significant tumor responses and subsequent survival benefits after the transfer of the CD gene to liver metastases and subsequent systemic treatment with the prodrug 5-FC (P < 0.0001). We describe reporter gene and survival experiments both in immunocompetent and athymic nude mice, establishing a gene expression pattern over time and characterizing the treatment effects of the virus delivery/prodrug system. Cure rates of up to 30% in animals with established liver metastases show that suicide gene therapy using TK- vaccinia virus as a vector may be a promising system for the clinical application of tumor-directed gene therapy.
 ...
PMID:Systemic administration of a recombinant vaccinia virus expressing the cytosine deaminase gene and subsequent treatment with 5-fluorocytosine leads to tumor-specific gene expression and prolongation of survival in mice. 1041 1

Infection of tumor cells by herpes simplex virus 1 (HSV-1) results in cell destruction and production of progeny virion in a process referred to as viral oncolysis. In this study, an HSV-1 mutant (HSV1yCD) was engineered such that the viral ribonucleotide reductase gene is disrupted by sequences encoding yeast cytosine deaminase, which efficiently metabolizes the prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU). HSV1yCD-infected cells convert 5-FC to 5-FU, which enhances cytotoxicity without significantly reducing viral replication and oncolysis. Oncolysis by a replicating HSV-1 mutant combined with therapeutic transgene delivery represents a new paradigm; HSV1yCD-infected cells are destroyed by viral replication, and uninfected cells are subjected to bystander killing from both progeny virion and extracellular diffusion of 5-FU. In contrast, HSV1yCD-mediated bioactivation of another prodrug, ganciclovir, impairs viral replication. HSV1yCD administered into the portal venous system replicates preferentially in liver metastases rather than normal liver. The anti-neoplastic activity of HSV1yCD combined with systemic 5-FC administration is greater than that achieved with HSV-1 replication alone. Combination oncolysis and prodrug bioactivation leads to significant prolongation of survival in mice with diffuse liver metastases.
 ...
PMID:Multimodality therapy with a replication-conditional herpes simplex virus 1 mutant that expresses yeast cytosine deaminase for intratumoral conversion of 5-fluorocytosine to 5-fluorouracil. 1145 90

Targeting of colorectal liver metastases by regional gene therapy was tested in a clinically relevant syngeneic model. First, the CEA-CD-113 retroviral vector containing the cytosine deaminase gene controlled by the CEA specific tumour cell promoter, was shown in vitro to convert 5-fluorocytosine to 5-fluorouracil, resulting in cancer cell killing with a large bystander effect. Second, 10 days after the establishment of liver metastases, retroviral vectors were delivered to the liver by hepatic artery injection. After 5-fluorocytosine administration for 7 days, most surface metastases disappeared and tumour volumes were suppressed up to 8.2-fold. The results support the development of this approach for patient treatment.
 ...
PMID:Hepatic intra-arterial delivery of a retroviral vector expressing the cytosine deaminase gene, controlled by the CEA promoter and intraperitoneal treatment with 5-fluorocytosine suppresses growth of colorectal liver metastases. 1150 57

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.
 ...
PMID:Naked DNA injection for liver metastases treatment in rats. 1198 64

Adenoviruses (Ads) that selectively replicate in tumor cells have shown promising preliminary results in clinical trials, especially in combination with chemotherapy. Here, we describe a system that combines the antitumor synergy of Ads and chemotherapeutic agents with the benefits of enzyme-activated prodrug therapy. In this system, a functional transgene expression cassette is created by homologous recombination during adenoviral DNA replication. Transgene expression is strictly dependent on viral DNA replication, which in turn is tumor specific. We constructed replication-activated Ad vectors to express a secreted form of beta-glucuronidase and a cytosine deaminase/uracil phosphoribosyltransferase, which activate the prodrugs 9-aminocamptothecin glucuronide to 9-aminocamptothecin and 5-fluorocytosine to 5-fluorouracil (5-FU) and further to 5-fluoro-UMP, respectively. We demonstrated replication-dependent transgene expression, prodrug activation, and induction of tumor cell toxicity by secreted beta-glucuronidase and cytosine deaminase/uracil phosphoribosyltransferase. Furthermore, exposure of cells to activated prodrug or drug at subtoxic concentrations enhanced viral DNA replication. Characteristically, these agents induced changes in the cell cycle status of exposed cells (G(2) arrest), which closely resembled the effect of wild-type Ad infection, and are thought to be favorable for viral replication. We tested a number of cytostatic drugs (camptothecin, etoposide, daunorubicin, cisplatin, 5-fluorouracil, hydroxyurea, Taxol, and actinomycin D) for their effect on viral DNA replication and found considerable differences between individual agents. Finally, we show that the combination of viral and prodrug therapy enhances viral replication and spread in liver metastases derived from human colon carcinoma or cervical carcinoma in a mouse model. Our data indicate that specific vector/drug combinations tailored to be synergistic may have the potential to improve the potency of either therapeutic approach. These data also provide a new rationale for expressing prodrug-activating enzymes from conditionally replicating Ads.
 ...
PMID:Enzyme-activated Prodrug Therapy Enhances Tumor-specific Replication of Adenovirus Vectors. 1241 33