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 efficacy of combination therapy with a "suicide gene" and a cytokine gene to treat metastatic colon carcinoma in the liver was investigated. Tumor in the liver was generated by intrahepatic injection of a colon carcinoma cell line (MCA-26) in syngeneic BALB/c mice. Recombinant adenoviral vectors containing various control and therapeutic genes were injected directly into the solid tumors, followed by treatment with ganciclovir. While the tumors continued to grow in all animals treated with a control vector or a mouse interleukin 2 vector, those treated with a herpes simplex virus thymidine kinase vector, with or without the coadministration of the mouse interleukin 2 vector, exhibited dramatic necrosis and regression. However, only animals treated with both vectors developed an effective systemic antitumoral immunity against challenges of tumorigenic doses of parental tumor cells inoculated at distant sites. The antitumoral immunity was associated with the presence of MCA-26 tumor-specific cytolytic CD8+ T lymphocytes. The results suggest that combination suicide and cytokine gene therapy in vivo can be a powerful approach for treatment of metastatic colon carcinoma in the liver.
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PMID:Combination gene therapy for liver metastasis of colon carcinoma in vivo. 770 88

In this report, we describe the use of two human colon carcinoma cell lines, HCT-8 and HT-29, as potential models to study DNA- and RNA-directed cytotoxicity due to 5-fluorouracil (FUra) exposure by flow microfluorimetric analysis of DNA cell content. The sensitivity of the HT-29 line (EC50 = 0.9 microM) to FUra was somewhat greater than that of the HCT-8 line (EC50 = 4 microM), but each presented a dramatically different DNA histogram after exposure to FUra. In HCT-8, an unexpected and nearly complete disappearance of cells in S-phase occurred, whereas in HT-29 the expected accumulation of cells at the G1-S border was observed. The absence of HCT-8 cells in S-phase also occurred as a result of two RNA polymerase inhibitors: actinomycin D and dichloro-D-ribofuranosylbenzimidazole. However, an accumulation of cells in S-phase was observed in the presence of 5-fluorodeoxyuridine. These results suggest that in the HCT-8 cell line, FUra predominantly causes an RNA-related toxicity. By comparison, the rate of formation of 5-fluorodeoxyuridine monophosphate, the increased dUMP pool size, and low thymidylate synthase activity in the HT-29 line are consistent with its greater susceptibility to DNA-directed toxicity. Further evidence was seen in the prevention of FUra cytotoxicity by thymidine in HT-29, but not in HCT-8 cells. Similarly, Leucovorin synergized the action of FUra in HT-29 but not in HCT-8. Enzymatic correlates supporting these observations are seen in the greater activity of uridine kinase than thymidine kinase (20:1) in HCT-8 cells compared with that in HT-29 cells (4:1).
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PMID:Aberrant cell cycle inhibition pattern in human colon carcinoma cell lines after exposure to 5-fluorouracil. 787 61

The effectiveness of combination therapy using a suicide gene and cytokine genes for the treatment of metastatic colon carcinoma in the mouse liver was investigated. Pre-established hepatic tumors treated with a recombinant adenoviral vector containing the herpes simplex virus thymidine kinase gene(tk) exhibited substantial regression, although all treated animals suffered from subsequent relapses. Although cotreatment with a mouse interleukin 2 (mIL-2)-containing adenoviral vector induced an effective antitumor immune response, the immunity waned with time, and the treated animals eventually succumbed to hepatic tumor relapse or distant metastases. In this study, mouse granulocyte macrophage colony-stimulating factor (mGM-CSF) gene was tested for its ability to further enhance and prolong the antitumoral cellular immunity. A fraction of the animals treated with tk + mIL-2 + mGM-CSF developed long-term antitumor immunity and survived for more than 4 months without recurrence. This long-term antitumor immunity could be enhanced further by subsequent "vaccination" with mIL-2-expressing parental tumor cells. The results indicate that local expression of GM-CSF in the hepatic tumors and prolonged mIL-2 expression are necessary to generate persistent antitumor immunity that is essential for the prevention of tumor recurrence and long-term animal survival.
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PMID:Combination suicide and cytokine gene therapy for hepatic metastases of colon carcinoma: sustained antitumor immunity prolongs animal survival. 870 21

The integration and expression of the herpes simplex virus type 1 thymidine kinase (HSV1-TK) gene in localized tumors results in tumor regression after the administration of the specific nucleoside analogue ganciclovir (GCV). Although only 10% to 20% of the tumor cells take up the HSV1-TK gene, the neighboring cells also die, a phenomenon termed "bystander effect.". In the present study, coinjection of the MC26 mouse colon carcinoma cell line and the HSV1-TK expressing retroviral packaging cell line followed after 7 days by the intraperitoneal administration of GCV resulted in almost total tumor regression in the immunocompetent BALB/c mice but not in immunocompromised athymic BALB/c mice. This suggested a strong cell-mediated immune component to the bystander effect.
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PMID:Prodrug-activated gene therapy: involvement of an immunological component in the "bystander effect". 872 6

Recombinant adenoviral mediated delivery of suicide and cytokine genes has been investigated as a treatment for hepatic metastases of colon carcinoma in mice. Liver tumors were established by intrahepatic implantation of a poorly immunogenic colon carcinoma cell line (MCA-26), which is syngeneic in BALB/c mice. Intratumoral transfer of the herpes simplex virus type 1 thymidine kinase (HSV-tk) and the murine interleukin (mIL)-2 genes resulted in substantial hepatic tumor regression, induced an effective systemic antitumoral immunity in the host and prolonged the median survival time of the treated animals from 22 to 35 days. The antitumoral immunity declined gradually, which led to tumor recurrence over time. A recombinant adenovirus expressing the mIL-12 gene was constructed and tested in the MCA-26 tumor model. Intratumoral administration of this cytokine vector alone increased significantly survival time of the animals with 25% of the treated animals still living over 70 days. These data indicate that local expression of IL-12 may also be an attractive treatment strategy for metastatic colon carcinoma.
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PMID:Adenovirus-mediated interleukin-12 gene therapy for metastatic colon carcinoma. 887 30

The two human colon carcinoma cell lines HT-29 and SW620, which stably express herpes simplex virus thymidine kinase (HSV-TK), are sensitized to the cytotoxic effects of the antiviral drug ganciclovir (GCV). Compared with HT-29 cells, SW620 cells were more sensitive to lower GCV concentrations (<1 microM), accumulated GCV triphosphate more rapidly, and incorporated higher levels of GCV into DNA. Following a 24-hr exposure to 10 microM GCV, bystander killing was as much as sixfold greater in SW620 cells than HT-29 cells. This bystander effect was dependent on the level of HSV-TK expression, the number of cells expressing HSV-TK, and the overall confluency of the cells. However, bystander killing did not correlate with gap junctional intercellular communication as determined by microinjection of Lucifer Yellow fluorescent dye. SW620 cells were coupled to <3% adjacent cells (compared with >50% for HT-29 cells), but were still able to transfer phosphorylated GCV to bystander cells as soon as 4 hr after drug was added. These results emphasize the importance of cell-specific metabolism in HSV-TK/GCV-mediated cytotoxicity and may suggest a novel mechanism for bystander killing.
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PMID:Differential ganciclovir-mediated cytotoxicity and bystander killing in human colon carcinoma cell lines expressing herpes simplex virus thymidine kinase. 958 3

The cytotoxicity of LY231514 was only partially alleviated by thymidine addition (5 microM) in GC3 human colon carcinoma cells, and complete protection required the addition of both hypoxanthine (100 microM) and thymidine. In contrast, the cytotoxic activity of tomudex (raltitrexed, ZD1694) was completely reversed by thymidine alone. MCF-7 human breast and H630 human colon carcinoma cells selected for resistance to tomudex and 5-fluorouracil, respectively via thymidylate synthase (TS) amplification demonstrated only modest resistance to LY231514 compared to tomudex. LY231514-induced cytotoxicity in these resistant cell lines was completely prevented by the addition of hypoxanthine (100 microM), indicating inhibition of purine de novo biosynthesis as a secondary target for LY231514 action. Thymidine at physiologic levels in mouse plasma (approximately 1 microM) produced only a 2.6-fold shift in the IC50 for LY231514-mediated cytotoxicity in GC3/cl1 cells compared to a 128-fold shift for tomudex. LY231514 treatment (i.p., qd x 10) significantly delayed tumor growth in the GC3 carcinoma xenograft model. However, a thymidine kinase-deficient mutant of this same tumor line demonstrated heightened sensitivity to the in vivo antitumor activity of LY231514 with complete regression of established tumors and a large number of tumor-free survivors after one course of treatment. The data demonstrate that inhibition of thymidylate synthase is a prominent mechanism for antitumor activity by LY231514, but important secondary sites of action exist for this multitargeted molecule.
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PMID:Role of thymidylate synthase in the antitumor activity of the multitargeted antifolate, LY231514. 1022 79

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.
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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

The feasibility of noninvasive imaging of adenoviral-mediated herpes virus type one thymidine kinase (HSV1-tk) gene transfer and expression was assessed in a well-studied animal model of metastatic colon carcinoma of the liver. Tumors were produced in syngeneic BALB/c mice by intrahepatic injection of colon carcinoma cells (MCA-26). Seven days later, three different doses (3 x 10(8), 1 x 10(8), and 3 x 10(7) plaque-forming units (pfu) of the recombinant adenoviral vector ADV. Rous sarcoma virus (RSV)-tk bearing the HSV1-tk gene were administered by intratumoral injection in separate groups of mice. Two control groups of tumor-bearing mice received intratumoral injections of the control adenoviral vector dl-312 or buffer alone, respectively. T2-weighted magnetic resonance (MR) images of mice were obtained before administering the virus and provided an anatomical reference of hepatic tumor localization. Eighteen h after the virus injection, one group of animals was given i.v. injections of 300 microCi of no-carrier-added 5-[131I]-2'-fluoro-1-beta-D-arabinofuranosyluracil (FIAU) and imaged 24 h later with a gamma camera. In some animals, the tumors were sampled and processed for histology and quantitative autoradiography (QAR). The gamma camera images demonstrated highly specific localization of [131I]FIAU-derived radioactivity to the area of ADV.RSV-tk-injected tumors in the liver, which was confirmed by coregistering the gamma camera and T2-weighted MR images. There was no accumulation of [131I]FIAU-derived radioactivity in tumors that were injected with the control vector or injection solution alone. A more precise distribution of radioactivity in the area of transfected tumor was obtained by histological and QAR comparisons. A heterogeneous pattern of radioactivity distribution in transfected tumors was observed. A punctate pattern of radioactivity distribution was observed in peritumoral liver tissue in animals given injections of 3 x 10(8) and 1 x 10(8) pfu of ADV.RSV-tk but not in animals given injections of 3 x 10(7) pfu nor in control animals. A QAR-microscopic comparison showed that the punctate areas of radioactivity colocalized with cholangial ducts. The level of [131I]FIAU-derived radioactivity accumulation (HSV1-tk expression) in the transfected tumors was viral dose-dependent. The viral dose-dependency of radioactivity accumulation was more pronounced in peritumoral liver, which was confirmed by reverse transcription-PCR analysis. A separate group of tumor-bearing animals received different doses of ADV.RSV-tk vector followed by treatment with ganciclovir (GCV), 10 mg/kg i.p. b.i.d. for 6 days. The ADV.RSV-tk transfected tumors significantly regressed with GCV treatment; the control tumors continued to grow. During the GCV treatment, the levels of liver transaminases (ALT and AST) were significantly increased in animals that received injections of 3 x 10(8) and 1 x 10(8) pfu of ADV.RSV-tk but not in animals that received injections of 3 x 10(7) pfu and in control animals. The observed liver toxicity confirms the results of gamma camera and QAR imaging, which demonstrated an unwanted spread of ADV.RSV-tk vector and HSV1-tk expression in peritumoral and remote liver tissue at higher doses. These and our previous results indicate that noninvasive imaging of adenoviral-mediated HSV1-tk gene expression is feasible for monitoring cancer gene therapy in patients.
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PMID:Imaging adenoviral-mediated herpes virus thymidine kinase gene transfer and expression in vivo. 1053 96

The goal of this study was to improve the therapeutic index of the herpes simplex virus-thymidine kinase/ganciclovir (HSV-tk/GCV) system by the addition of thymidylate synthase (TS) inhibitors. For this, we assessed the potential of GCV to synergistically interact with 5-fluorouracil (5-FU), ZD1694 (Tomudex), and (E)-5-(2-bromovinyl)-2'-deoxyuridine in HSV-tk-expressing murine MC38 STK and human HT-29 STK colon carcinoma cell lines. Synergistic cell killing was observed in a clonogenic assay over most of the cytotoxic dose range by the median-effect principle of Chou and Talalay (T. C. Chou and P. Talalay, Adv. Enzyme Regul., 22: 27-55, 1984). In a s.c. HT-29 STK xenograft tumor model, we demonstrated that the combination of GCV and 5-FU resulted in statistically significant enhanced animal survival over single-agent treatment. Furthermore, we showed that the combination of GCV and ZD1694 in association with the HSV-tk/GCV system was at least as effective as GCV/5-FU in vitro and in vivo. The mechanism for the observed synergy is most likely attributable to the increased GCV phosphorylation in the presence of the tested TS inhibitors. Our data suggest that the HSV-tk/GCV metabolic suicide gene transfer system could serve as an adjuvant of the presently used TS inhibitors, thus potentially improving the efficacy of present cancer gene therapy approaches.
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PMID:Enzyme prodrug gene therapy: synergistic use of the herpes simplex virus-cellular thymidine kinase/ganciclovir system and thymidylate synthase inhibitors for the treatment of colon cancer. 1053 2


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