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

---

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

Gene therapy of cancer is a novel approach with the potential to selectively eradicate tumour cells, whilst sparing normal tissue from damage. In particular, gene-directed enzyme prodrug therapy (GDEPT) is based on the delivery of a gene that encodes an enzyme which is non-toxic per se, but is able to convert a prodrug into a potent cytotoxin. Several GDEPT systems have been investigated so far, demonstrating effectiveness in both tissue culture and animal models. Based on these encouraging results, phase I/II clinical trials have been performed and are still ongoing. The aim of this review is to summarise the progress made in the design and application of GDEPT strategies. The most widely used enzyme/prodrug combinations already in clinical trials (e.g., herpes simplex 1 virus thymidine kinase/ganciclovir and cytosine deaminase/5-fluorocytosine), as well as novel approaches (carboxypeptidase G2/CMDA, horseradish peroxidase/indole-3-acetic acid) are described, with a particular attention to translational research and early clinical results.
...
PMID:Gene directed enzyme/prodrug therapy of cancer: historical appraisal and future prospectives. 1124 46

Liver metastasis is the most serious event for physicians and surgeons treating patients with colorectal cancer. Gene therapy is expected to become a novel strategy to prevent liver metastasis. Four types of clinical studies are currently underway: 1) suicide-gene therapy with the cytosine deaminase gene; 2) immune gene therapy with cytokine (inter leukin-2) or major histocompatibility complex class I gene HLA-B7; 3) tumor suppressor gene p53 therapy; and 4) lysis of p53 mutant cancer cells with E1B55k-deleted adenovirus (Onyx-015). Basic research provided several candidates for the liver metastasis-associated genes, including MMP7, DCC, CDC25B, E-cadherin, CD44, vascular endothelial growth factor, etc. There is an alternative approach to liver metastasis, which attempts to introduce a specific gene such as cytosine deaminase and TIMP-2 into the hepatocytes but not into the tumor itself. This concept is based on results showing that hepatocytes can incorporate genes more readily than cancer cells can. Recently, mutant virus therapy has been developed, which includes Onyx-015, adenovirus dl922-947, and mutant-type herpes simplex virus. These mutant types of virus specifically proliferate in the cancer cells and result in their lysis. In the future, development of gene delivery systems that are powerful and specific to cancer type is essential.
...
PMID:[Future scope for gene therapy for liver metastasis of colon cancer]. 1139 6

The efficacy of combination suicide gene therapy was evaluated using a Herpes simplex virus-thymidine kinase/ganciclovir (HSV-TK/GCV) system and an Escherichia coli cytosine deaminase/5-fluorocytosine (CD/5-FC) system on the LNCaP human prostate cancer cell model. Two types of plasmid vectors with the HSV-TK gene were constructed. A constitutive chicken beta-actin promoter drove one and a prostate-specific antigen (PSA) promoter drove the other. Similarly, a pair of plasmids with the CD gene under a cytomegalovirus (CMV) promoter and the PSA promoter was also constructed. LNCaP cells were transfected in vitro with either or both of those plasmids using a cationic lipid reagent. Transfected cells were treated with GCV and/or 5-FC. The percentage of viable LNCaP cells 7 days after treatment with HSV-TK/GCV or CD/5-FC under a constitutive promoter was 40% and 41% of controls, respectively. The cell viability when two suicide genes were combined was 23%. The cell viabilities after four days with PSA promoter-HSV-TK vectors, CD vectors and a combination of both were 79%, 88% and 88%, respectively. Suicide gene therapy using either HSV-TK/GCV, CD/5-FC, or both, was effective in the LNCaP model. An additive effect was observed when the two suicide genes were used together. The PSA promoter did not seem to be effective enough to elicit cytotoxicity under the experimental conditions used here.
...
PMID:Suicide gene therapy on LNCaP human prostate cancer cells. 1144 69

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

Tumor cells that express a fusion gene of Escherichia coli cytosine deaminase (CD) and herpes simplex virus type 1 thymidine kinase (TK) sequences activate and are subsequently killed by the nontoxic prodrugs 5-fluorocytosine and ganciclovir. We have previously developed a recombinant adenovirus containing the CD-TK fusion gene controlled by the human inducible heat shock protein 70 promoter so that heat at 41 degrees C for 1 hour induces therapeutic gene expression. This adenovirus effectively transduces heat-inducible expression of the CD-TK gene into human prostate carcinoma cells. However, because a limited number of cells in a tumor can actually be infected, we created a replicating adenoviral vector to increase CD-TK gene expression. This vector is a replication-competent, E1B-attenuated adenoviral vector containing the hsp70 promoter-driven CD-TK gene (Ad.E1A(+)HS-CDTK). When human prostate adenocarcinoma DU-145 cells (mutant p53) were infected with the virus at a multiplicity of infection (MOI) of 1 or 10, the viral replication was detected within 2 days at both MOIs. Similar results were observed in human colorectal carcinoma CX-1 cells. When DU-145 cells were infected with the virus at an MOI of 10, incubated for 24 hours, heated at 41 degrees C for 4 hours, and then harvested 20 hours later, Western blot analysis demonstrated that this virus successfully produced viral E1A proteins and heat shock stimulated the CD-TK gene expression by 12.3-fold. In addition, Ad.E1A(+)HS-CDTK effectively suppressed cell proliferation by viral cytopathic effect). Unlike with a replication-incompetent virus (Ad.HS-CDTK), the cytopathic effect of the virus and cytotoxicity in the presence of the prodrugs were still observed even at low MOI (MOI=1.0).
...
PMID:Replicating adenoviral vector-mediated transfer of a heat-inducible double suicide gene for gene therapy. 1149 59

The in vivo gene delivery of E. coli cytosine deaminase (cd) cDNA and systemic 5-fluorocytosine (5-FC) administration have been studied extensively because of their clinical relevance to cancer gene therapy. This approach has the potent advantage of a stronger bystander effect compared to the previous thymidine kinase suicide gene system of the herpes simplex virus. However, 5-fluorouracil (5-FU), an active metabolite in cd with 5-FC therapy, is not always effective for every type of tumor since the enzymes responsible for further drug metabolism vary significantly in each tissue. In this study, we aimed to increase the sensitivity of 5-FU by transduction of thymidine phosphorylase (dThdPase) cDNA into brain tumor cells. After retroviral transfer of the cDNA, we obtained 9L murine gliosarcoma cells showing stable expression of the target enzyme (9L-dThdPase). The growth of the cells was identical to wild type (9L-WT) or control-vector transfected (9L-Neo) cells in vitro. Sensitivity to 5-FU was increased in 9L-dThdPase cells. After the adenoviral delivery of cytosine deaminase gene into these cells, 9L-dThdPase cells also demonstrated an increased sensitivity to 5-FC. Moreover, we showed that transduction of dThdPase cDNA prolongs the survival of animals bearing intracerebral tumors after experimental in vivo cytosine deaminase gene therapy. These results suggest that transduction of thymidine phosphorylase may be a beneficial approach to increasing the efficacy of cd/5-FC suicide gene therapy in certain types of tumor.
...
PMID:Transduction of thymidine phosphorylase cDNA facilitates efficacy of cytosine deaminase/5-FC gene therapy for malignant brain tumor. 1172 81

Enzymes, the expression products of transferred or native genes, offer unique windows of opportunity for clinical diagnosis and therapy. Although some expression products can be monitored in plasma, nuclear medicine imaging (SPECT and PET) offers the unique ability to selectively measure the intensity and regional/spatial distribution of gene expression both in vivo, in situ. Importantly, the superior sensitivity and moderate spatial resolution of the nuclear techniques also enable in vivo kinetic characterization of enzyme-substrate interaction. Indeed, the non-invasive, whole-body assessment of gene expression can only be achieved through imaging techniques. Given today's technology, nuclear imaging techniques uniquely provide the necessary sensitivity required to evaluate the success of the gene delivery and expression (transcription and translation), and to detect unwanted expression by non-target tissues. Enzymes are a special class of proteinacious gene expression products that selectively bind specific substrates for the purpose of molecular biotransformation rather than for signal transduction. In general, enzymes have received much less attention for imaging than receptors and antibodies, despite the enzymes' high substrate specificity and the potential for kinetic evaluation. Enzymes are attractive targets for diagnostic imaging and radioisotope radiotherapy because they convert multiple molecular copies of the substrate (radiotracer) per molecule of enzyme, thereby greatly increasing the ultimate sensitivity relative to the sensitivity offered by receptors that bind with 1:1 stoichiometry. Not surprisingly, enzymes have been the preferred molecular targets to date for scintigraphic imaging of gene therapy. This overview describes opportunities and advances in the utilization of radiolabelled nucleosides and nucleoside bases for imaging in gene therapy, with emphasis on the exploitation of enzyme systems for scintigraphic imaging of gene expression in gene therapy of cancer. Herpes simplex virus type-1 thymidine kinase and bacterial/fungal cytosine deaminase are discussed within the context of gene therapy issues such as gene vectors for targeting and delivery, the bystander effect, and radionucleoside delivery. The utilization of nucleosides as markers of tissue proliferation is discussed with respect to selected enzyme targets.
...
PMID:Enzyme-targeted, nucleoside-based radiopharmaceuticals for scintigraphic monitoring of gene transfer and expression. 1177 56

The genome sequence of Plasmodium falciparum, the causative agent of the most severe form of malaria in humans, rapidly approaches completion, but our ability to genetically manipulate this organism remains limited. Chromosomal integration has only been achieved following the prolonged maintenance of circularised episomal plasmids which selects for single crossover recombinants. It has not been possible to construct genetic deletions via double crossover recombination, presumably due to the low frequency of this event. We have used the Herpes simplex virus thymidine kinase gene and the Escherichia coli cytosine deaminase gene for negative selection of P. falciparum. Parasites were transformed with plasmids expressing the thymidine kinase and cytosine deaminase genes by positive selection for the human dihydrofolate reductase gene. Parasites expressing thymidine kinase are susceptible to the pro-drug ganciclovir while those expressing cytosine deaminase are sensitive to 5-fluorocytosine. Parental parasites were inherently resistant to these drugs. A significant 'bystander effect' was evident in cultures with either ganciclovir or 5-fluorocytosine. Positive and negative selection of the thymidine kinase transformants with both ganciclovir and WR99210 resulted in the selection of parasites containing a genetic deletion of the Pfrh3 gene, the first targeted double crossover deletions in P. falciparum. The use of negative selection for gene disruptions via double crossover recombination will dramatically improve our ability to analyse protein function and opens the possibility of using this strategy for a variety of gene deletion and modification experiments in the analysis of this important infectious agent.
...
PMID:Negative selection of Plasmodium falciparum reveals targeted gene deletion by double crossover recombination. 1179 25

We have previously developed a recombinant adenovirus containing a fusion gene of Escherichia coli cytosine deaminase (CD) and herpes simplex virus type 1 thymidine kinase (HSV-1 TK) controlled by a cytomegalovirus (CMV) enhancer-promoter. This replication-incompetent adenovirus effectively transduced the CD-TK gene into human prostate adenocarcinoma DU-145 or PC-3 cells. Interestingly, heat shock at 41 degrees C for 4 hours elevated the level of CD-TK by approximately 5- to 20-fold at a multiplicity of infection (MOI) of 1. Heat-enhanced expression of CD-TK promoted cytotoxicity by 23-, 9-, or 47-fold in the presence of 50 microg/mL ganciclovir (GCV), 500 microg/mL 5-fluorocytosine (5-FC), or 50 microg/mL GCV+500 microg/mL 5-FC, respectively, at an MOI of 1. Moreover, there was an increase in radiosensitivity when adenovirus-infected cells were heated at 41 degrees C for 4 hours followed by irradiation in the presence of the prodrugs. Virus+heat+1 microg/mL GCV treatment increased radiosensitivity by a dose-modifying factor (DMF) of 2.2, whereas virus+heat+10 microg/mL 5-FC exposure resulted in a DMF of 2.3. Radiosensitization was clearly enhanced as a result of combined prodrug exposure (DMF=4.4). Our results suggest that the efficiency in expression of suicide genes from an adenoviral vector used for cytotoxic anticancer therapy could be improved by combining heat treatment with radiation therapy.
...
PMID:Gene transfer into human prostate adenocarcinoma cells with an adenoviral vector: Hyperthermia enhances a double suicide gene expression, cytotoxicity and radiotoxicity. 1189 43

Standard chemotherapeutic agents and ionizing radiation destroy dividing cells. Because tumor cells divide more rapidly than normal cells, there is a therapeutic index in which damage to the cancer cells is maximized while keeping the toxicity to the normal host cells acceptable. Suicide gene therapy strives to deliver genes to the cancer cells, which convert nontoxic prodrugs into active chemotherapeutic agents. With this strategy, the systemically administered prodrug is converted to the active chemotherapeutic agent only in cancer cells, thereby allowing a maximal therapeutic effect while limiting systemic toxicity. A literature search was conducted using the MEDLINE database from 1990 to 2001 to identify articles related to suicide gene therapy for cancer. A number of suicide gene systems have been identified, including the herpes simplex virus thymidine kinase gene, the cytosine deaminase gene, the varicella-zoster virus thymidine kinase gene, the nitroreductase gene, the Escherichia coli gpt gene, and the E. coli Deo gene. Various vectors, including liposomes, retroviruses, and adenoviruses, have been used to transfer these suicide genes to tumor cells. These strategies have been effective in cell culture experiments, laboratory animals, and some early clinical trials. Advances in tissue- and cell-specific delivery of suicide genes using specific promoters will improve the clinical utility of suicide gene therapy.
...
PMID:Current progress in suicide gene therapy for cancer. 1194 67


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---