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)

Advanced peritoneal carcinomatoses is very difficult to treat. We have explored the potential therapeutic application of gene therapy using cationic liposomes in this disease. The lacZ gene was introduced in vitro into ovarian and endometrial cancer cells using cationic liposomes. The transfection efficiency was similar to that of commercially available liposomes in serum-free medium (11.0-20.9% vs. 5.4-26.0%). In serum-containing medium, the efficiency was 1.9-18.1%, which is comparable with the efficiency in serum-free medium. However, the efficiency of commercial liposomes decreased drastically to between 0.1% and 4.7% in the serum-containing medium. When cultured cells were transfected with the herpes simplex virus thymidine kinase (HSV-tk) gene and ganciclovir (GCV) was added, the anti-tumor effect of GCV was 47-640 times greater than when the same experiment was performed with lacZ gene. Evaluation of anti-tumor effect was performed with the MTT assay. In vivo, the HRA and mEIIL ascitic mice were treated with HSV-tk gene and GCV using the peritoneal route, a significant prolongation of the mean survival time was observed by Kaplan-Meier analysis (16-18 days and 15-30 days, respectively, p < 0.05). These results indicate a potential role for gene therapy in the treatment of advanced intraperitoneal carcinomatoses using the novel cationic liposomes.
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PMID:In vitro and in vivo evaluation of novel cationic liposomes utilized for cancer gene therapy. 1679 60

Two technical hurdles, gene delivery and target specificity, have hindered the development of effective cancer gene therapies. In order to circumvent the problem of tumor specificity, the suicide gene, HSV-1 thymidine kinase (HSV-Tk), was modified with a complex 5' upstream-untranslated region (5'-UTR) that limits efficient translation to cells expressing high levels of the translation initiation factor, eIF4E. Since previous studies have shown that most tumor cells express elevated levels of eIF4E, tumor-specific gene delivery was optimized by incorporation of the 5'-UTR-modified suicide gene (HSV-UTk) into an adenovirus vector (Ad-CMV-UTk). The efficacy of this novel approach of targeting suicide gene expression and limiting cytotoxicity by means of translational restriction was tested in vitro with the use of the human breast cancer cell lines (MCF-7, MDA-MB435, and ZR-75-1). As controls, normal MCF10A, HMEC, and HMSC cell lines that express relatively low levels of eIF4E were used. Real-time reverse-transcription polymerase chain reaction (RT-PCR) was used to quantify HSV-Tk mRNA for cells infected with Ad-CMV-UTk as well as with Ad-CMV-Tk (a control adenovirus in which HSV-Tk is not regulated at the level of translation). Translation of HSV-Tk in the Ad-infected cells was measured by Western blot analysis. In addition, cytotoxicity was determined following treatment with the pro-drug ganciclovir (GCV) using an MTT viability assay. Finally, microPET imaging was used to assess cancer cell-specific expression of HSV-Tk and expression in normal tissues in vivo after intraperitoneal injection of Ad-CMV-Tk or Ad-CMV-UTk. These data collectively showed enhanced cancer cell-specific gene expression and reduced normal tissue gene expression for the Ad-HSV-UTk compared to the Ad-CMV-Tk, leading to increased cancer cell-enhanced GCV cytotoxicity. These results indicate that translational targeting of suicide gene expression in tumor cells in vitro and in vivo is effective and may provide a platform for enhanced cancer gene therapy specificity.
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PMID:Cancer-specific targeting of an adenovirus-delivered herpes simplex virus thymidine kinase suicide gene using translational control. 1680 1

We have assessed the effect of combine cancer gene therapy with exogenous human tumor necrosis factor alpha (hTNFalpha) and suicide gene therapy on three human cancer cell lines MCF-7 (breast adenocarcinoma), U-118MGand 42-MG-BA (human gliomas). Transfection of a plasmid containing hTNFalpha under the control of a hybrid promoter resulted in expression of hTNFalpha gene in vitro. Transduction of retroviral plasmid containing Herpes simplex thymidine kinase (HSVtk) led to the expression of thymidine kinase in all three cell lines. MTT cell proliferation assay and flow cytometric analysis showed a significant increase in apoptotic and necrotic cells and decrease of proliferation in all cell lines after combine therapy with hTNFalpha expression plus thymidine kinase/GCV suicide system. The presence of these two genes after transduction of retroviral vector containing thymidine kinase and hTNFalpha was confirmed by PCR. The expression of HSVtk gene was proved by Western blot analysis, and the expression of both genes was confirmed by RT-PCR. Additive cell killing effect due to presence of HSVtk and hTNFalpha therapeutic genes after activation of non-toxic prodrug was observed. Whether the bicistronic plasmid containing both genes would improve the therapeutic effect need to be assessed in the future.
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PMID:Combine cancer gene therapy harnessing plasmids expressing human tumor necrosis factor alpha and Herpes simplex thymidine kinase suicide gene. 1701 29

Antiviral drugs alone have been unsuccessful in the treatment of Epstein-Barr virus (EBV)-associated malignancies because the virus maintains a latent state of replication in these tumors. In recent years, novel therapeutic approaches are being investigated wherein lytic replication of the virus is induced prior to the use of cytotoxic antiviral drugs. The choice of suitable agents to induce lytic replication has been a critical step in this novel approach. We have previously demonstrated that butyrate derivatives induce a lytic pattern of EBV gene expression in patient-derived EBV-positive lymphoblastoid cell lines and, together with nucleoside analogue ganciclovir, effectively reduce or eliminate tumor growth in humans. Butyrate has drawbacks as a therapeutic agent, however, as constant intravenous infusion is required to achieve detectable plasma levels of this drug. In this study, we investigated whether discontinuous exposure to butyrate is capable of initiating lytic phase gene expression and thymidine kinase induction, and sensitizing EBV-positive lymphoma cells to ganciclovir-mediated cell growth arrest and apoptosis. We demonstrate that multiple daily 6-h exposures of the EBV-positive Burkitt's lymphoma cell line P3HR1 to butyrate induced sustained expression of the EBV lytic phase protein BMRF. Viral thymidine kinase was also induced by intermittent exposure, although to a lower level than with continuous exposure treatment. However, discontinuous exposure to butyrate in combination with ganciclovir induced a similar level of tumor cell growth inhibition as did continuous treatment, as measured by serial enumeration of viable cells, MTT cell proliferation assays and measurement of cellular DNA content. We further demonstrated that those cells which survived initial exposure to butyrate plus ganciclovir remained susceptible to further cycles of combination treatment. These findings suggests that continuous infusion of butyrate may not be necessary for maintaining viral thymidine kinase gene expression and sensitization to antiviral agents in EBV-associated tumors, and that therapeutic regimens which employ more convenient, discontinuous exposure to butyrate may also be effective clinically.
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PMID:Short, discontinuous exposure to butyrate effectively sensitizes latently EBV-infected lymphoma cells to nucleoside analogue antiviral agents. 1716 33

The killing effects of herpes simplex virus thymidine kinase gene/ganciclovir (HSV-tk/GCV) approach by the addition of several commonly clinical chemotherapeutic agents on hormone refractory prostate cancer (HRPC) cells PC-3m were investigated. After transferring of the HSV-tk gene into PC-3m cells, mRNA and protein expression of HSV-tk was detected by reverse-transcript polymerase chain reaction (RT-PCR) and strept avidin-biotin complex (SABC) immunohistochemical method. The killing effect of GCV, cisplatin (CDDP), etoposide (VP-16), vincristine (VCR), methotrexate (MTX), 5-fluorouracil (5-Fu), and suramin on PC-3m cells was evaluated by morphological assessment analysis, trypan blue exclusion assay and MTT assay respectively. Additionally, the cooperative effect of HSV-tk/GCV system combined with the above agents on the target cancer cells was determined by MTT. Furthermore, apoptosis and necrosis induced by GCV plus 5-Fu or suramin was analyzed by flow cytometry (FCM). The results showed that that there was HSV-tk mRNA and protein expression in pDR2-tk plasmid transduced PC-3m cell. Combination of GCV with VP-16, VCR, 5-Fu or suramin led to an enhanced cellular killing effect, but with CDDP resulted in a reduced one and with MTX in an approximate one. FCM revealed that synergistic use of GCV and 5-fu or suramin resulted in a rather large proportion of apoptosis and necrosis with the apoptosis index being 36.38% and 35.51%, and the proportion of necrosis being 33.05% and 28.87%, respectively. In conclusion, HSV-tk/CGV approach by addition of certain clinical available chemotherapeutic drugs brings on statistically significant enhanced cell killing over single-agent treatment. Our results highlight the potential for such new combination therapies for future treatments of HRPC.
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PMID:Cooperative therapeutic effects of herpes simplex virus thymidine kinase gene/ganciclovir system and chemotherapeutic agents on prostate cancer in vitro. 1721 83

The multidrug resistance (mdr) mediated by P-glycoprotein (P-gp), the mdr1 gene product, is one of the major obstacles in leukemia treatment. The present study was designed to explore a suicide gene therapy approach targeting mdr1 for reversal of P-gp-mediated mdr in the mdr positive K562/A02 cells. To study targeted killing effects of cytosine deaminase (CD)-thymidine kinase (TK) fusion suicide gene on multi-drug resistant leukemia, the CD-TK fusion suicide gene expression vector driven by mdr1 promoter was constructed and transferred into K562 and K562/A02 cells using lipofectintrade mark 2000. RT-PCR was used to demonstrate that there were CD and TK genes expression in K562/A02 cells, but not in K562 cells. MTT analysis showed that, compared with that in K562/CDTK, the survival rate of K562/A02-CDTK cells decreased and at the same time the apoptotic rate increased after treatment with GCV and 5-FC (P < 0.05). In vivo studies showed that the tumor volume in the prodrug treated K562/A02-CDTK groups was significantly less than that in the NS-control and K562-CDTK groups (P < 0.05). These findings show that the CD and TK fusion suicide gene expression driven by mdr1 promoter is effective in killing multidrug resistant K562/A02 cells.
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PMID:Antitumor effects of cytosine deaminase and thymidine kinase fusion suicide gene under the control of mdr1 promoter in mdr1 positive leukemia cells. 1770 92

Transferrin modified pro-cationic liposomes were prepared and used to investigate the effect of targeting therapeutic genes to human hepatoma carcinoma cells in vitro. The main lipid CHETA, cholest-5-en-3beta-yl[2-[[4-[(carboxymethyl)dithio]-1-iminobutyl]amino]ethyl] carbamate (C36H61N3O4S2), was synthesized and used to prepare pro-cationic liposomes. The thymidine kinase (TK) gene loaded pro-cationic liposomes were prepared by first mixing the plasmid DNA and protamine together, and then incubating the resulted polyplexes with blank pro-cationic liposomes preformed by the thin film dispersion-sonication method. Transferrin (Tf) was adsorbed on the surface of pro-cationic liposomes via electrostatic interactions to form transferrin modified pro-cationic liposomes. Cellular association was measured by fluorimetry at excitation and emission wavelengths of 490 and 520 nm, respectively. The viability of TK gene infected cells following administration of ganciclovir (GCV) was investigated by MTT assay. The transferrin modified TK gene pro-cationic liposomes had a mean diameter of 240 +/- 12 nm and zeta potential of -24.10 +/- 2.5 mV (n = 3). The transmission electron microscopy image indicated that most of the liposomes were relatively regular and spherical with a condensed core inside. Cell-associated fluorescence of Tf-liposomes and unmodified liposomes (without transferrin) was 7.8 x 10(6), and 3.2 x 10(6) per milligram protein, respectively. Compared to Lipofectamine 2000 (Invitrogen, USA) the pro-cationic liposomes and transferrin modified pro-cationic liposomes had less cytotoxicity to cells. The transduced TK gene HepG2 cells were more sensitive to GCV than the un-transduced TK gene ones and the human normal Chang liver cells were not affected by the TK/GCV system mediated by procationic liposomes.
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PMID:Preparation of a TK/GCV administration system mediated by transferrin modified pro-cationic liposomes. 1771 94

Adenovirus (ADV)-mediated gene therapy with the thymidine kinase (TK) gene under control of the Rous sarcoma virus (RSV) promotor followed by the administration of acyclovir has been established in vitro for the treatment of ovarian cancer cells and has been used as the basis for intraperitoneal phase I clinical trials. It is unclear how long a significant degree of transgene translation can be expected after adenovirus-mediated TK transduction, where the transcriptional complex is localized in the nucleus in an episomal fashion and thus without stable integration. The possible interaction of acyclovir pretreatment with subsequent ADV-RSV-TK transduction also remains to be elucidated. Transgene expression and cell killing efficacy were analysed based on multiplicity of infection (MOI) and MTT assay. Anti-TK-antibody 1397 was used for immunocytochemistry and Western blot analysis of TK expression. After transduction with ADV-RSV-TK at an MOI of 66, TK translation increased strongly in MDH 2774 and OVCAR-3 cell lines during the initial 48 hours. Virtually constant expression of the TK transgene was observed by Western blot during eight days. Cell killing efficacy was increased by repeated daily administrations of acyclovir. Pretreatment with acyclovir did not result in significantly increased cell killing efficacy. No negative effect of acyclovir on ADV-RSV-TK transduction was observed. The at least week-long expression of the TK transgene with persistently increasing efficacy of cell killing after ADV-mediated tumor cell transduction provide a realistic basis for the development of multicycle ADV-mediated TK gene therapy approaches in the treatment of ovarian cancer. Continuous i.v. acyclovir treatment or daily oral acyclovir-prodrug therapy might simplify the substrate regimen for the TK gene.
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PMID:Persistent adenovirus-mediated thymidine kinase gene expression in ovarian cancer cells increases cell killing efficacy over time. 1903 80

Coxsackie adenovirus receptor (CAR) expression is the main mechanism of adenovirus entry into target cells. It is unclear whether CAR expression itself is influenced by transduction with the adenovirus-Rous sarcoma virus-thymidine kinase (ADV-RSV-TK) gene therapy construct or by the subsequent intracellular accumulation of the TK gene product. Antibody generation and characterization, immunocytochemistry, Western blotting and 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay were performed to investigate the relationship of gene transfer and CAR expression as well as differences in therapeutic susceptibility of MDAH-2774 and OVCAR-3 cell lines to ADV-RSV-TK gene therapy. CAR expression was observed on the membranes but intracellular translocation of CAR also took place dependent on cellular growth patterns. TK gene expression was dependent on multiplicity of infection (MOI) and thus on vector dose in a linear fashion. Neither TK expression nor ADV transduction influenced CAR expression, or ADV-RSV-TK transduction. Differential susceptibility of different cell lines to TK-induced cell killing by acyclovir metabolites was observed. CAR expression appears not to be influenced by adenoviral transduction or by the accumulation of the TK gene product. Differences in therapeutic sensitivity are most likely mediated by intracellular mechanisms and not by modulation of CAR expression.
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PMID:Adenovirus-mediated thymidine kinase gene therapy and coxsackie adenovirus receptor expression in ovarian cancer cells. 1928 72

The effects of ghrelin on the proliferation and differentiation of 3T3-L1 preadipocytes and the possible mechanisms were investigated in this study. 3T3-L1 preadipocytes were cultured in vitro and treated with different concentrations of ghrelin. Proliferation of 3T3-L1 preadipocytes was evaluated by MTT method and mRNA levels of c-myc and thymidine kinase were detected by RT-PCR. Morphological changes of 3T3-L1 preadipocytes were observed and cell differentiation was measured by oil red O staining. The mRNA levels of peroxisome proliferator-activated receptor gamma (PPARgamma) and CAAT/enhancer binding protein (C/EBPalpha) in the cells at different differentiation stages were detected by RT-PCR. The results showed that ghrelin at concentrations of 10(-7) to 10(-15) mol/L could significantly promote preadipocyte proliferation (P<0.05), with the most pronounced effect observed at 10(-11) mol/L (P<0.01). Treatment of 3T3-L1 preadipocytes with ghrelin significantly increased the mRNA levels of c-myc and thymidine kinase (P<0.01). Morphological findings demonstrated that the great amount of lipid droplets appeared in the 3T3-L1 preadipocytes treated with ghrelin. Ghrelin could morphologically induce the differentiation of 3T3-L1 preadipocytes into mature adipocytes. Ghrelin significantly increased the mRNA levels of PPARgamma and C/EBPalpha during the differentiation, when compared with control group (P<0.05). The mRNA levels of PPARgamma and C/EBPalpha were obviously up-regulated with the differentiation of preadipocytes after the treatment of ghrelin. There were significant difference in the mRNA levels of PPARgamma and C/EBPalpha on day 2 and day 8 of the differentiation of 3T3-L1 preadipocytes (P<0.01). In conclusion, ghrelin could promote the proliferation and differentiation of 3T3-L1 preadipocytes by increasing the mRNA levels of PPARgamma and C/EBPalpha and therefore enhance the sensitivity of adipocytes against insulin.
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PMID:Effects of ghrelin on the proliferation and differentiation of 3T3-L1 preadipocytes. 1939 10


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