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)

The growth of the adenocarcinoma cell line derived from human salivary gland (HSG) is regulated by all-trans-retinoic acid (t-RA), which binds to its specific receptor, retinoic acid receptors (RARs), located in the nucleus, and thereby transactivates target genes. In this study, we examined the binding characteristics of the nuclear extract of HSG cells to the retinoic acid response element (RARE) compared with those of in vitro translated RAR alpha and retinoid X receptor alpha (RXR alpha), a heterodimeric partner of RAR alpha. Gel shift analysis using anti-RAR alpha and anti-RXR alpha antibodies revealed that the translated RAR alpha bound to RARE as a heterodimer with RXR alpha. In contrast, the binding of the nuclear extract of HSG cells to RARE showed a heterogeneous pattern, suggesting the existence of several species of RXRs as well as RARs in the nuclei of HSG cells. We therefore tried to clone these putative RXRs by the polymerase chain reaction using degenerated oligonucleotide primers conserved across the RXR family. The DNA sequencing of the recombinant clones revealed the expression of RXR alpha and RXR beta. In addition, chicken ovalbumin upstream promoter-transcription factor I (COUP-TFI), which is also an RXR family member, was cloned. To evaluate the transcriptional activity of RARs and RXRs endogenously expressed in HSG cells, we performed a transient transfection analysis. When HSG cells were transfected with a luciferase reporter plasmid containing two repeats of either the RARE of the RAR beta gene or that of cellular retinol-binding protein II gene, positioned upstream of a thymidine kinase promoter fused to the luciferase sequence, a 2-3-fold induction of luciferase activity was observed in both cases. These results suggest that RARs and RXRs endogenously expressed in HSG cells were transcriptionally active in vivo. Thus, our findings showed that RXR alpha, RXR beta, and COUP-TFI are expressed in HSG cells and suggest that these molecules function as heterodimeric partners of RARs and (or) competitive repressors for RAREs and are involved in cellular responses mediated by retinoids.
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PMID:Expression of retinoid X receptors and COUP-TFI in a human salivary gland adenocarcinoma cell line. 959 64

Irinotecan [7-ethyl-10-(4-[1-piperidino]-1-piperidino)-carbonyloxy-camptothec in] administered i.v. in two courses, each course consisting of administration every day for 5 days [(dx5)2] on days 1-5 and 8-12, has demonstrated significant activity against advanced human tumor xenografts derived from colon adenocarcinomas and several childhood cancers. To build on this therapy, we have evaluated the combination of irinotecan given on this schedule with 5-fluorouracil given on days 1, 7, and 14 with or without leucovorin [(dx5)3 i.v.] against colon tumors, or combined with etoposide administered (dx5)2 i.v. either 2 h before or 2 h after irinotecan for treatment of colon tumors and rhabdomyosarcomas. A combination of 5-fluorouracil at 75% and irinotecan at 50% of their respective maximum tolerated doses when administered as single agents on this schedule gave acceptable toxicity. Against colon adenocarcinoma xenografts, 5-fluorouracil did not enhance the response rate compared with that obtained with the optimum dose of irinotecan given as a single agent. Against GC3/TK- xenografts, which lack thymidine kinase and cannot salvage thymidine to circumvent the inhibition of thymidylate synthase, the addition of leucovorin to the combination increased the complete response rate from 10 to >90%, whereas the response rates for the optimal doses of irinotecan or 5-fluorouracil, as single agents, were 30 and <10%, respectively. Etoposide d x 5 i.v. for two or three courses or (d x 5)3 p.o. did not cause objective regression of any colon tumors. In contrast, three of five rhabdomyosarcoma lines demonstrated a high frequency of partial regressions or complete regressions when treated (d x 5)1 i.v. Repetitive courses [e.g., (d x 5)2 or (d x 5)3] i.v. or p.o. or by 4-h infusion d x3 i.v. were either equally effective or less effective. Irinotecan and etoposide were combined using the (d x 5)2 i.v. schedule for both drugs, in which irinotecan was given 2 h before or 2 h after the administration of etoposide. Each drug could be combined at only 38% of its respective maximum tolerated dose when administered as a single agent, indicating greater than additive toxicity. Toxicity was similar irrespective of the sequence of administration and was manifested by loss of weight (73% of the initial weight, nadir day 7), myelosuppression, and prolonged thrombocytopenia. The responses of colon carcinomas to the combination given in either sequence were similar to that achieved with irinotecan given alone at the same dose as used in the combination. Similarly, when etoposide was given before irinotecan, the responses of rhabdomyosarcomas were similar to those for irinotecan. However, in experiments in which etoposide was administered 2 h after each dose of irinotecan, there was significant antagonism of the antitumor activity of irinotecan.
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PMID:Evaluation of irinotecan in combination with 5-fluorouracil or etoposide in xenograft models of colon adenocarcinoma and rhabdomyosarcoma. 981 97

Apigenin, a flavinoid, and lovastatin, an HMG-CoA reductase inhibitor, upregulated gap junction (GJ) function and dye transfer in tumors expressing GJ and were inactive in the GJ-negative tumor line N2a. N2a cells transfected with the connexin 43 gene showed restored cell-to-cell dye transfer, which could then be improved nearly fourfold by addition of apigenin. To test the drugs in HSV thymidine kinase/ganciclovir (HSV-tk/GCV) tumor killing, mixtures of 90% wild-type (WT) with 10% HSV-tk gene-modified MCA38 adenocarcinoma cells were exposed in vitro to GCV +/- apigenin or lovastatin. A significant bystander effect (BSE) was seen following GCV treatment alone, while neither apigenin or lovastatin alone had any effect on the recovery of viable tumor colonies. However, GCV-treated cultures also exposed to apigenin or lovastatin showed an increased BSE and reduced tumor cell recovery. Thirty percent of mice bearing tumors from the same mixture of 90% WT and 10% HSV-tk MCA38 cells treated with GCV alone became tumor free. Tumor-bearing mice given only two or three injections of lovastatin or apigenin during GCV treatment had a doubling of the antitumor response rate, with 60-70% of the mice achieving complete remission. These results support the hypothesis that the transfer of phosphorylated GCV from HSV-tk gene-expressing cells to neighboring WT tumor cells is a major component of the BSE and that pharmacological manipulation of GJ function with lovastatin or apigenin can result in striking improvement in the antitumor response in mice with tumors modified to contain as few as 10% HSV-tk cells.
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PMID:Enhancement of the herpes simplex virus thymidine kinase/ganciclovir bystander effect and its antitumor efficacy in vivo by pharmacologic manipulation of gap junctions. 982 37

Inoperable adenocarcinoma in colon or lung shows resistance to conventional anti-cancer therapy. For these cancers, the feasibility of transcriptionally targeted killing of carcinoembryonic antigen (CEA)-producing adenocarcinoma cells was investigated. Adenovirus vectors carrying a CEA promoter to express E. coli lacZ (AdCEALacZ) or herpes simplex thymidine kinase (AdCEATK) were made and their in vitro and in vivo tumoricidal effects on CEA-producing or non-producing colon and lung cancer cells were evaluated. In vitro infection with AdCEALacZ showed significantly higher CEA promoter-driven lacZ expression in CEA-producing adenocarcinoma cells including VMRC-LCD and LoVo than in CEA-non-producing cells. AdCEATK-infected LoVo showed higher sensitivity to ganciclovir than control vector-infected LoVo or AdCEATK-infected HeLa both in vitro and in subcutaneously implanted tumors of nude mice. Moreover, total tumor elimination in vivo was achieved by either pre-infection of as few as 30% of cells comprising tumors or by direct in vivo injection of AdCEATK to pre-established LoVo tumors. In addition, CEA promoter-driven lacZ expression in LoVo cells was enhanced by the addition of interleukin-6 (IL-6) in vitro. These results provide a rationale for CEA-promoter-driven, adenovirus-mediated gene therapy for CEA-producing adenocarcinomas in colon and lung with reduced toxicity to normal cells.
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PMID:Transcriptionally targeted in vivo gene therapy for carcinoembrionic antigen-producing adenocarcinoma. 1059 10

Tumor-directed gene therapy, such as "suicide gene" therapy, requires high levels of gene expression in a high percentage of tumor cells in vivo to be effective. Current vector strategies have been ineffective in achieving these goals. This report introduces the attenuated (thymidine kinase (TK)-negative) replication-competent vaccinia virus (VV) as a potential vector for tumor-directed gene therapy by studying the biodistribution of VV in animal tumor models. A TK-deleted recombinant VV (Western Reserve strain) expressing luciferase on a synthetic promoter was constructed. Luciferase activity was measured in vitro after transduction of a variety of human and murine tumor cell lines and in vivo after intraperitoneal (i.p.) delivery in C57BL/6 mice with 7-day i.p. tumors (10(6) MC-38 cells). Three other in vivo tumor models were examined for tumor-specific gene expression after intravenous delivery of VV (human melanoma in nude mice, adenocarcinoma liver metastasis in immunocompetent mice, and subcutaneous sarcoma in the rat). In addition, a replication-incompetent vaccinia (1 microg of psoralen and ultraviolet light, 365 nm, 4 minutes) was tested in vitro and in vivo and compared with active virus. Luciferase activity in i.p. tumors at 4 days after i.p. injection of VV was >7000-fold higher than lung, >3000-fold higher than liver, and >250-fold higher than ovary. In addition, intravenous injection of VV resulted in markedly higher tumor luciferase activity compared with any other organ in every model tested (up to 188,000-fold higher than liver and 77,000-fold higher than lung). Inactivation of the virus resulted in negligible gene expression in vivo. In summary, VV has a high transduction efficiency in tumor cells with high levels of gene expression. The results suggest a selective in vivo replication of TK-deleted VV in tumor cells. Replication competent, TK-deleted VV appears to be an ideal vector for testing the in vivo delivery of toxic genes to tumor cells.
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PMID:Vaccinia as a vector for tumor-directed gene therapy: biodistribution of a thymidine kinase-deleted mutant. 1067 58

For specific transduction of herpes simplex virus thymidine kinase (HSV-tk) into human small-cell lung carcinoma (SCLC) cells, we explored the 5'-flanking region (-1.1 kb) of the gastrin-releasing peptide (GRP) gene as a lung cancer-specific promoter. RT-PCR analysis demonstrated expression of GRP mRNA in the SBC5 human SCLC cell line but not in the RERF human SCLC cell line, the A549 human lung adenocarcinoma cell line or the HeLa human uterine cervix epithelioid carcinoma cell line. A reporting vector containing the GRP promoter (pGL2-GRP) exhibited higher luciferase activity in SBC5 than in the other 3 cell lines. After transfecting an expression vector containing the GRP promoter-bound HSV-tk gene (pGRP-TK) into the cells, we measured their sensitivity to ganciclovir (GCV). In SBC5, pGRP-tk-transfected cells became about 100 times more sensitive to GCV than parental cells in vitro. In nude mice, tumors of pGRP-tk-transfected SBC5 regressed completely after i.p. administration of GCV. GRP promoter might be a good tool for tumor-specific transduction of suicide genes in GRP-expressing SCLC cells.
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PMID:Use of gastrin-releasing peptide promoter for specific expression of thymidine kinase gene in small-cell lung carcinoma cells. 1069 54

Exposure of cells to ionising radiation results in the activation of specific transcriptional control (CArG) elements within the early growth response 1 (Egr1) gene promoter, leading to increased gene expression. As part of a study investigating the potential use of these elements in radiation-controlled gene therapy vectors, we have incorporated their sequences into a synthetic gene promoter and assayed for the ability to induce expression of a downstream reporter gene following irradiation. In vector-transfected MCF-7 breast adenocarcinoma cells, the synthetic promoter was more effective than the wild-type Egr1 counterpart in up-regulating expression of the reporter gene after exposure to a single 5 Gy dose, and equally effective as the wild-type in U87-MG glioma cells. The level of gene expression achieved using the synthetic promoter was dependent on the inducing radiation dose for both U87-MG and MCF-7 cells, being maximal at 3 Gy and decreasing at 5 and 10 Gy. Furthermore, induction could be repeated by additional radiation treatments. The latter indicates that up-regulation should be additive during fractionated radiotherapy schedules. To demonstrate the potential clinical benefit of such an approach, the synthetic promoters were also shown to drive expression of the herpes simplex virus thymidine kinase gene, leading to enhanced cell killing in the presence of the prodrug ganciclovir (GCV) when compared with cells treated with radiation alone. Our results demonstrate that the synthetic promoter is responsive to low doses of ionising radiation and therefore isolated CArG elements function as radiation-mediated transcriptional enhancers outside their normal sequence context. The continued development and optimisation of such radiation-responsive synthetic promoters is expected to make a valuable contribution to the development of future radiation-responsive vectors for cancer gene therapy.
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PMID:Development of synthetic promoters for radiation-mediated gene therapy. 1108 80

A recombinant MVMp of the fibrotropic strain of minute virus of mice (MVMp) expressing the chloramphenicol acetyltransferase reporter gene was used to infect a series of biologically relevant cultured cells, normal or tumor-derived, including normal melanocytes versus melanoma cells, normal mammary epithelial cells versus breast adenocarcinoma cells, and normal neurons or astrocytes versus glioma cells. As a reference cell system we used normal human fibroblasts versus the SV40-transformed fibroblast cell line NB324K. After infection, we observed good expression of the reporter gene in the different tumor cell types, but only poor expression if any in the corresponding normal cells. We also constructed a recombinant MVMp expressing the green fluorescent protein reporter gene and assessed by flow cytometry the efficiency of gene transduction into the different target cells. At a multiplicity of infection of 30, we observed substantial transduction of the gene into most of the tumor cell types tested, but only marginal transduction into normal cells under the same experimental conditions. Finally, we demonstrated that a recombinant MVMp expressing the herpes simplex virus thymidine kinase gene can, in vitro, cause efficient killing of most tumor cell types in the presence of ganciclovir, whilst affecting normal proliferating cells only marginally if at all. However, in the same experimental condition, breast tumor cells appeared to be resistant to GCV-mediated cytotoxicity, possibly because these cells are not susceptible to the bystander effect. Our data suggest that MVMp-based vectors could prove useful as selective vehicles for anticancer gene therapy, particularly for in vivo delivery of cytotoxic effector genes into tumor cells.
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PMID:Tumor-selective gene transduction and cell killing with an oncotropic autonomous parvovirus-based vector. 1082 6

Several experimental approaches have been tested for suicide gene delivery into tumor cells, including viral and non-viral vectors. In this study, we compared the efficiency of Herpes Simplex Virus type 1 thymidine kinase gene (HSV-tk) delivery by retrovirus-producing cells and DNA/liposome complexes for the treatment of peritoneal carcinomatosis induced in syngeneic rats by DHD/K12 colorectal adenocarcinoma cells. After in vitro determination of the best transduction conditions, rats were treated with multiple intraperitoneal injections of plasmid DNA containing one or two copies of CMV-driven HSV-tk gene (pCMV-TK and p(CMV-TK)2, respectively) associated with LipofectAMINE, each injection being followed by a Ganciclovir (GCV) course. Animals treated by DNA/liposome complexes and GCV or with retrovirus-producing cells and GCV showed a similar increase of survival as compared to the control group. After DNA/ liposome injections, expression of the tk transgene was detected in tumor nodes (epiploon) and also in liver, lung, spleen, bowels and brain. The expression was not homogeneous throughout the different organs and most likely reflected the transfection of only a limited number of cells.
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PMID:Similar efficiency of DNA-liposome complexes and retrovirus-producing cells for HSV-tk suicide gene therapy of peritoneal carcinomatosis. 1085 40

Nucleoside kinases from several species are investigated as "suicide genes" for treatment of malignant tumors by combined gene/chemotherapy. We have recently cloned a multisubstrate deoxyribonucleoside kinase of Drosophila melanogaster (Dm-dNK), and we have shown that the enzyme phosphorylates cytotoxic pyrimidine and purine nucleoside analogs. The broad substrate specificity of the enzyme, as well as its very high catalytic rate, makes it a unique member of the nucleoside kinase enzyme family. In the present study, we evaluated Dm-dNK as a suicide gene by constructing a replication-deficient retroviral vector that expresses the enzyme. The human pancreatic adenocarcinoma cell line MIA PaCa-2 and a thymidine kinase-deficient osteosarcoma cell line were transduced with the recombinant virus. We showed that Dm-dNK can be expressed in human cells, that the enzyme retained its enzymatic activity, and that it is localized in the cell nuclei due to a nuclear localization signal in its C-terminal region. The cells expressing Dm-dNK exhibited increased sensitivity to several cytotoxic nucleoside analogs, such as 1-beta-d-arabinofuranosylcytosine, 1-beta-d-arabinofuranosylthymine, (E)-5-(2-bromovinyl)-2'-deoxyuridine, 2-chloro-2'-deoxyadenosine, and 2',2'-difluorodeoxycytidine. These findings suggest that Dm-dNK may be used as a suicide gene in combined gene/chemotherapy of cancer.
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PMID:Retroviral transduction of cancer cell lines with the gene encoding Drosophila melanogaster multisubstrate deoxyribonucleoside kinase. 1099 93


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