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:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A group of unnatural 1-(2-deoxy-beta-D-ribofuranosyl)-2,4-difluorobenzenes having a variety of C-5 two-carbon substituents [-C...C-X, X = I, Br; -C...CH; (E)-CH=CH-X, X = I, Br; -CH=CH2; -CH2CH3; -CH(N3) CH2Br], designed as nucleoside mimics, were synthesized for evaluation as anticancer and antiviral agents. The 5-substituted (E)-CH=CH-I and -CH2CH3 compounds exhibited negligible cytotoxicity in a MTT assay (CC50 = 10(-3) to 10(-4)M range), relative to thymidine (CC50 = 10(-3) to 10(-5)M range), against a variety of cancer cell lines. In contrast, the C-5 substituted -C...C-I and -CH(N3)CH2Br compounds were more cytotoxic (CC50 = 10(-5) to 10(-6)M range). The -C...C-I and -CH2CH3 compounds exhibited similar cytotoxicity against non-transfected (KBALB, 143B) and HSV-1 TK+ gene transfected (KBALB-STK, 143B-LTK) cancer cell lines expressing the herpes simplex virus type 1 (HSV-1) thymidine kinase gene (TK+). This observation indicates that expression of the viral TK enzyme did not provide a gene therapeutic effect. The parent group of 5-substituted compounds, that were evaluated using a wide variety of antiviral assay systems [HSV-1, HSV-2, varicella-zoster virus (VZV), vaccinia virus, vesicular stomatitis, cytomegalovirus (CMV), and human immunodeficiency (HIV-1, HIV-2) viruses], showed that this class of unnatural C-aryl nucleoside mimics are inactive and/or weakly active antiviral agents.
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PMID:Synthesis of 1-(2-deoxy-beta-D-ribofuranosyl)-2,4-difluoro-5-substituted-benzenes: "thymine replacement" analogs of thymidine for evaluation as anticancer and antiviral agents. 1130 62

Oka varicella vaccine has been used to confer active immunity to varicella-zoster virus (VZV) in healthy and immunocompromised hosts. Based on its attenuated nature, Oka varicella vaccine expressing human immunodeficiency virus (HIV) env antigen was constructed by inserting the HIVenv gene into the viral genome and its immunogenicity was assessed in guinea pigs. The HIVenv gene encoding 296-463 amino acids was inserted between the sequences of the hepatitis B surface antigen and the thymidine kinase gene of the cloned plasmid and the recombinant virus was isolated by cotransfection of the chimeric plasmid with viral DNA. Insertion of the HIVenv gene into the viral genome was confirmed by PCR and sequencing of the viral genome of the recombinant virus. The recombinant virus expressed 30k HIVenv fusion protein in its infected cells. In guinea pigs, immunization with the recombinant virus induced an antibody response to both the HIV antigen and the V3 peptide of gp120 as well as VZV gE:gI. Cell-mediated immunity to the HIV antigen and gE:gI was assessed by the cutaneous reaction representing delayed type hypersensitivity. Immunized guinea pigs responded well to both the HIV antigen and gE:gI. Thus the recombinant Oka varicella vaccine expressing the HIVenv antigen induced both a humoral and cell-mediated immunity to the HIV antigen similar to VZV as Oka varicella vaccine induces humoral and cell-mediated immunity to VZV in the vaccinees. This recombinant Oka varicella vaccine expressing the HIVenv antigen may be evaluated for its immunogenicity as one of the AIDS vaccine candidates.
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PMID:Construction of Oka varicella vaccine expressing human immunodeficiency virus env antigen. 1136 Feb 39

Lymphoproliferative diseases (LPDs) associated with the Epstein-Barr virus (EBV) include non-Hodgkin lymphomas, which occur in the setting of immunosuppression, including that induced by human immunodeficiency virus, and posttransplant lymphoproliferative disorders. These LPDs are characterized by actively proliferating, latently infected EBV-positive B lymphocytes and often follow a rapidly progressive fatal clinical course. Pharmacologic treatment for herpesvirus infections has targeted the virus-specific enzyme, thymidine kinase (TK), with nucleoside analogs. The lack of viral TK expression in EBV-positive tumors, caused by viral latency, however, makes antiviral therapy alone ineffective as an antineoplastic therapy. Arginine butyrate selectively activates the EBV TK gene in latently infected EBV-positive tumor cells. We have developed a strategy for treatment of EBV-associated lymphomas using pharmacologic induction of the latent viral TK gene and enzyme in tumor cells using arginine butyrate, followed by treatment with ganciclovir. A phase I/II trial, using an intrapatient dose escalation of arginine butyrate combined with ganciclovir, is underway. This combination therapy has produced complete clinical responses in 5 of 10 previously refractory patients, with partial responses occurring in 2 additional patients. This virus-targeted antitumor strategy may provide a new therapeutic approach to EBV-associated neoplasms.
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PMID:Induction of the Epstein-Barr virus thymidine kinase gene with concomitant nucleoside antivirals as a therapeutic strategy for Epstein-Barr virus-associated malignancies. 1155 13

Mother-to-child transmission of the human immunodeficiency virus is substantially reduced by prenatal and postnatal treatment with anti-retroviral nucleoside analogues; however, the long-term consequences of these drug interventions are not known. The nucleoside analogue zidovudine (3'-azido-2',3'-dideoxythymidine; AZT) is carcinogenic in mice when administered transplacentally or neonatally, and this may be due to a genotoxic mechanism. Since single-drug treatment with AZT is being superseded by multidrug combinations, we have investigated the induction of mutations and micronuclei in mice treated neonatally with AZT, lamivudine (3'-thia-2',3'-dideoxycytidine; 3TC), or a combination of the two drugs. B6C3F(1)/Tk+/- mice were treated daily from days 1-8 of age with 200 mg AZT/kg/day, 200 mg 3TC/kg/day, or a mixture of 200 mg AZT + 200 mg 3TC/kg/day (AZT/3TC). One and 2 days after the last dose, bone marrow was collected to assess the induction of micronuclei in polychromatic erythrocytes; 3 weeks following treatment, the induction of mutants was determined in the hypoxanthine-guanine phosphoribosyltransferase (Hprt) and thymidine kinase (Tk) genes of spleen lymphocytes. AZT and AZT/3TC, but not 3TC, caused a significant increase in micronuclei, with the response being greatest one day after the last dose. None of the drugs induced mutations in the Hprt gene, while AZT and AZT/3TC, but not 3TC, caused a significant increase in the Tk mutant frequency. The increase in Tk mutants by AZT and AZT/3TC was associated with loss of the wild-type (Tk+) allele (loss of heterozygosity). These data suggest that AZT, but not 3TC, is genotoxic in neonatal mice, and that 3TC does not alter significantly the responses observed with AZT alone.
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PMID:Frequency of Tk and Hprt lymphocyte mutants and bone marrow micronuclei in B6C3F(1)/Tk+/- mice treated neonatally with zidovudine and lamivudine. 1218 83

Molecular imaging is broadly defined as the characterization and measurement of biological processes in living animals, model systems, and humans at the cellular and molecular level using remote imaging detectors. One underlying premise of molecular imaging is that this emerging field is not defined by the imaging technologies that underpin acquisition of the final image per se, but rather is driven by the underlying biological questions. In practice, the choice of imaging modality and probe is usually reduced to choosing between high spatial resolution and high sensitivity to address a given biological system. Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) inherently use image-enhancing agents (radiopharmaceuticals) that are synthesized at sufficiently high specific activity to enable use of tracer concentrations of the compound (picomolar to nanomolar) for detecting molecular signals while providing the desired levels of image contrast. The tracer technologies strategically provide high sensitivity for imaging small-capacity molecular systems in vivo (receptors, enzymes, transporters) at a cost of lower spatial resolution than other technologies. We review several significant PET and SPECT advances in imaging receptors (somatostatin receptor subtypes, neurotensin receptor subtypes, alpha(v)beta(3) integrin), enzymes (hexokinase, thymidine kinase), transporters (MDR1 P-glycoprotein, sodium-iodide symporter), and permeation peptides (human immunodeficiency virus type 1 (HIV-1) Tat conjugates), as well as innovative reporter gene constructs (herpes simplex virus 1 thymidine kinase, somatostatin receptor subtype 2, cytosine deaminase) for imaging gene promoter activation and repression, signal transduction pathways, and protein-protein interactions in vivo.
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PMID:Molecular imaging of gene expression and protein function in vivo with PET and SPECT. 1235 50

Reportedly, in human immunodeficiency virus type 1 (HIV) vectors, insertion of central polypurine tract (cPPT) increased expression of transgenes for a short period. To test this for a stable condition, we constructed a series of vectors carrying a Neo(r) gene as a stable marker driven by a synthetic thymidine kinase (hTK) promoter. Transduction efficiency was increased in about 2-fold and decreased in about 8-fold by insertion of the reported 178bp and our 282bp cPPTs, respectively. PCR analyses revealed that insertion of 282bp cPPT, but not 178bp cPPT, impaired integration, although it did not deteriorate nuclear transport much. Furthermore, we found that insertion of 282bp cPPT between hTK promoter and an upstream LTR sequence reduced reporter gene activity in about 5-fold. This inhibitory effect of 282bp cPPT may partly account for the observed decrease in transduction efficiency. We suggest that actual effect of cPPT insertion should be examined in each HIV vector.
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PMID:Inhibitory and enhancing effects of insertion of central polypurine tract sequence on gene expression with vectors derived from human immunodeficiency virus type 1. 1261 60

Expression cloning of cDNAs is a powerful tool with which to identify genes based on their specific functional properties. Here we describe the development of a cDNA library transfer system based on the human immunodeficiency virus type-1 (HIV). This system represents an improvement over current oncoretroviral cDNA expression systems in terms of target cell range and the inclusion of a selectable marker. By use of a simple packaging system, we were able to produce high-titer vector stocks from HIV vector-based cDNA libraries and demonstrate highly efficient cDNA expression cloning in three model experiments. First, HOS TK(-) cells, which are null for thymidine kinase (TK) expression, were transduced with an HIV-based cDNA library derived from primary human foreskin fibroblasts (HFFs) and functionally selected for TK expression. In a second experiment, hypoxanthine guanine phosphoribosyltransferase-1-deficient (HPRT(-)) fibroblasts were transduced with a T cell (PM1) line-derived cDNA library and selected for HPRT expression. Both TK (frequency 1 in 5.0 x 10(4)) and HPRT (frequency 1 in 2.0 x 10(4)) cDNAs were readily isolated from these HIV-based cDNA libraries. As a third example, we demonstrated the ability of this vector system to allow functional cDNA library screens to be performed in primary, mitotically inactive cell types. Using senescent HFFs as a target cell population, we were able to isolate SV40 large T antigen cDNA-containing clones (frequency 1 in 2.5 x 10(4)) based on their ability to overcome the senescence-induced block to cell proliferation. Thus, this system can be used to clone relatively low-abundance cDNAs based upon their expression. Because of the ability of HIV-based vectors to transduce primary and nondividing cells efficiently, this vector system will further broaden the range of cell types in which expression cloning studies can be performed.
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PMID:Development of an HIV-based cDNA expression cloning system. 1284 40

It has been proposed that the declining efficiency of antiretroviral agents in human immunodeficiency virus (HIV) infection may also depend on cellular factors at their site of action. Two in particular have been proposed: (i) the defective intracellular metabolism of NRTI in target cells and the altered uptake; and (ii) efflux of nucleoside reverse transcriptase inhibitors (NRTI) and protease inhibitors (PI) by cellular transporter molecules. Several studies have shown that: changes in the activities of various purine and pyrimidine biosynthetic enzymes may occur in lymphocytes of HIV-infected patients; HIV-infected patients on prolonged treatment with nucleoside analogues, e.g. zidovudine, show significantly decreased activity of thymidine kinase (TK) compared with untreated HIV-infected people; and NRTI and PI are substrates for the multidrug membrane transporters. With regard to the latter issue, it is known that the ATP-binding cassette transporter proteins such as the P-glycoprotein (MDR), and the newly discovered family of multidrug resistance-associated proteins (MRP1-6), promote the active extracellular efflux of a wide variety of therapeutics drugs and overexpression of some of them lowers intracellular concentration of PI. In the very near future such mechanisms, also called 'cellular drug resistance', might be taken into account, together with other immunological, virological and behavioural factors, to explain the 'drug failure' and/or the variability of response in HIV patients undergoing antiretroviral treatment.
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PMID:Cellular issues relating to the resistance of HIV to antiretroviral agents. 1500 May 83

The antiviral drug 2',3'-didehydro-3'-deoxythymidine (D4T; also know as stavudine and Zerit), which is used against human immunodeficiency virus (HIV), causes delayed toxicity (peripheral neuropathy) in long-term use. After examining a series of 2',3'-didehydro-3'-deoxy-4'-substituted thymidine (4'-substituted D4T) analogs, 4'-ethynyl D4T was found to have a fivefold-better antiviral effect and to cause less cellular and mitochondrial toxicity than D4T. The antiviral activity of this compound can be reversed by dThd but not by dCyd. The compound acted synergistically with beta-L-2',3'-deoxy-3'-thiacytidine (also known as lamivudine) and beta-L-2',3'-dideoxy-2',3'-didehydro-5-fluorocytidine (also known as elvucitabine) and additively with 2',3'-dideoxyinosine (also known as didanosine and Videx) and 3'-azido-3'-deoxythymidine (also known as Retovir and zidovudine) against HIV. 4'-Ethynyl D4T is phosphorylated by purified human thymidine kinase 1 (TK-1) from CEM cells with a faster relative V(max) and a lower K(m) value than D4T. The efficiency of TK-1 in the phosphorylation of 4'-ethynyl D4T is fourfold better than that of D4T. While D4T is broken down by the catabolic enzyme thymidine phosphorylase, the level of breakdown of 4'-ethynyl D4T was below detection. Since 4'-ethynyl D4T has increased anti-HIV activity and decreased toxicity and interacts favorably with other currently used anti-HIV drugs, it should be considered for further development as an anti-HIV drug.
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PMID:Novel 4'-substituted stavudine analog with improved anti-human immunodeficiency virus activity and decreased cytotoxicity. 1510 15

The nucleoside analog zidovudine (3'-azido-3'-deoxythymidine, AZT), by itself or in combination with other anti- retroviral drugs, is used perinatally to prevent mother to child transmission of human immunodeficiency virus type 1. AZT is mutagenic in vitro and mutagenic and carcinogenic when administered to neonatal mice. A previous study indicated that the anti-retroviral agent didanosine (2',3'-dideoxyinosine, ddI) potentiated the mutagenicity of AZT in the thymidine kinase (TK) gene of cultured human TK6 lymphoblastoid cells. We have evaluated whether or not ddI affects the in vivo genotoxicity of AZT by breeding C57Bl/6N/Tk+/- female mice with C3H/HeNMTV male mice and treating the offspring daily on postnatal days 1-8 with 200 mg/kg ddI alone or in combination with 200 mg/kg AZT. One day after the last dose, bone marrow polychromatic erythrocytes (PCEs) were obtained to assess the induction of micronuclei; 3 weeks following treatment, the induction of mutants was determined in the hypoxanthine-guanine phosphoribosyltransferase (Hprt) and Tk genes of splenic T lymphocytes from B6C3F1/Tk+/- mice. The mixture of AZT and ddI, but not ddI alone, caused a significant increase in micronucleated PCEs. When assessed 3 weeks after dosing, ddI did not induce mutations in the Hprt or Tk genes. The mixture of AZT and ddI also did not induce mutations in the Hprt gene, but did induce a significant increase in Tk mutants, similar to that observed previously with AZT alone. The induction of mutations in the Tk gene by the mixture of AZT and ddI was associated with loss of the wild-type Tk+ allele. These data indicate that, under the conditions of this experiment, ddI is not mutagenic in neonatal B6C3F1/Tk+/- mice and that it does not potentiate the mutagenicity of AZT.
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PMID:Frequency of Tk and Hprt lymphocyte mutants and bone marrow micronuclei in mice treated neonatally with zidovudine and didanosine. 1521 30


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