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)

We investigated whether the transduction of a suicide gene might induce the elimination of malignant solid tumours. BDIX male rats were given an intra-hepatic injection of a mixture containing DHDK12 tumor cells and xenogeneic fibroblasts. The latter were producing either the herpes simplex virus type 1 thymidine kinase HSV1-TK- or nls-lac Z(control)-expressing recombinant retroviral particles. 5 days later, a time at which the tumor is macroscopic, all the rats were treated with ganciclovir, a nucleoside analog that is metabolized by HSV1-TK into a toxic compound. After 5 days of treatment, a dramatic reduction in tumour volume was noted in the HSV1-TK group. These results delineate a new therapeutical strategy for the treatment of disseminated liver metastases or of a large variety of solid malignant tumours.
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PMID:[Treatment of experimental liver tumors by in vivo suicide gene transfer in rats]. 133 22

The herpes simplex virus type 1 thymidine kinase (HSV1-TK) converts nontoxic nucleoside analogs such as ganciclovir into phosphorylated compounds that act as chain terminators and specifically kill dividing cells. This property could be exploited for the treatment of tumors that are made up of rapidly dividing cells invading a nonproliferating tissue. For this purpose, specific expression of the suicide gene into dividing tumor cells can be further targeted by using retroviral-mediated gene transfer. We investigated whether the direct intratumoral transduction of a suicide gene might induce the elimination of malignant solid tumors. Rats with established macroscopic liver metastases were given an intratumoral injection of packaging cells producing either HSV1-TK- or lacZ-expressing recombinant retroviral particles. All rats were next treated with ganciclovir. A dramatic regression of the tumor volume was observed in the HSV1-TK-treated animals. The residual tumors were mostly made up of a massive fibrotic reaction, with the mean cancer cell mass being reduced approximately 60-fold compared to controls. In some animals, the residual tumors were devoid of cancer cells. This treatment efficacy appears in part due to a "bystander effect" in which phosphorylated ganciclovir could be transferred from cell to cell and to an active local immune reaction evidenced by massive infiltration of the tumors by macrophages and both CD4+ and CD8+ lymphocytes. This efficient therapeutic approach might be an ultimate treatment for disseminated liver metastases in humans and could also be applied to treatment of a large variety of solid tumors.
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PMID:Regression of established macroscopic liver metastases after in situ transduction of a suicide gene. 834 12

Metastases of breast cancer are a major cause of treatment failure. To evaluate the therapeutic efficacy of suicide gene therapy in metastatic breast cancer, we used the herpes simplex virus thymidine kinase (HSV-tk) gene followed by ganciclovir (GCV) administration to treat breast cancer, generated by an adenocarcinoma cell line MOD in syngeneic mice. The bystander effect of HSV-tk + GCV on tumor cell killing was illustrated by demonstrating complete regression of subcutaneous tumors consisting of 90% parental tumor cells and 10% HSV-tk transformed tumor cells. To establish a model of breast cancer metastases in the liver, tumors were generated by intra-hepatic implantation of MOD cells in syngeneic animals. Two weeks after tumor cell implantation, replication defective adenoviral vectors expressing HSV-tk (ADV.tk), or beta-galactosidease (ADV. beta-Gal) were injected intratumorally, followed by buffer or GCV administration. Treatment with ADV.tk + GCV resulted in significant regression of tumor (P < .001), as assessed by computerized morphometric analysis of residual tumor. This was reflected as a significant prolongation of survival in treated animals (P < .001). These results demonstrate that ADV-mediated suicide gene therapy in vivo can be incorporated in a comprehensive treatment strategy for liver metastases of breast cancer.
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PMID:Adenoviral-mediated suicide gene therapy for hepatic metastases of breast cancer. 889 53

Hepatic metastasis of colon cancer is an important prognostic factor for survival. In this study, we examined the effect of gene therapy using the herpes simplex virus-thymidine kinase (HS-tk) gene with short-course ganciclovir (GCV) treatment for multiple hepatic metastases of murine colon cancer. Colon26 cells transfected with the HS-tk gene were found to be sensitive to GCV in a concentration-dependent way. On the other hand, induction of the HS-tk gene in the cells had no influence on cell growth in vitro. However, multiple hepatic metastases of Colon26 cells transfected with HS-tk gene were significantly suppressed by the GCV treatment. These results thus suggest that HS-tk gene therapy is useful for the treatment of hepatic metastasis in colon cancer.
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PMID:Effect of gene therapy with the herpes simplex virus-thymidine kinase gene on hepatic metastasis in murine colon cancer. 903 98

Metastases of lung cancer are a major cause of treatment failure. To evaluate the therapeutic efficacy of gene therapy in metastatic lung cancer, we used adenoviral (ADV) mediated transfer of the herpes simplex virus thymidine kinase (HSV-tk) gene and the cytokine gene interleukin-2 (IL-2) to treat a murine model of metastatic lung cancer in the liver. Hepatic metastases were established by intrahepatic implantation of LL2 cells in syngeneic recipient mice. One week after tumor implantation, various replication defective ADV vectors were injected intratumorally. Treatment with a vector expressing the HSV-tk followed by ganciclovir administration with ADV.tk resulted in significant regression of tumor (p<0.01) as well as prolongation of survival (p<0.001). While a vector expressing mouse IL-2 ADV.IL-2 alone was ineffective, combination therapy with HSV-tk resulted in further tumor regression and improvement of animal survival (p<0.05). These results demonstrate that suicide and cytokine genes can be utilized in combination to treat metastatic lung cancer in vivo.
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PMID:Combination therapy with suicide and cytokine genes for hepatic metastases of lung cancer. 936 77

The use of so-called 'suicide' genes to activate prodrugs has been effective in animal models for several solid tumor types and is now in phase I and II clinical trials. We have exploited adenovirus vectors (Ad) for transfer and expression of the herpes simplex virus thymidine kinase (HSVtk) gene to render rat colorectal liver metastases sensitive to the anti-herpetic agent ganciclovir (GCV). The efficacy and toxicity of this enzyme-prodrug combination were tested after in situ transduction of rat colorectal tumor cells and after intraportal administration of the vector Ad.CMV.TK. Our results demonstrate the validity of the approach but reveal that hepatic expression of HSVtk, both in tumor bearing and in tumor-free rats, provokes severe liver dysfunction and mortality upon GCV administration. These data show, that in contrast to the common assumption, normally non-mitotic tissues too, can be affected by adenovirus-mediated HSVtk transfer and subsequent GCV treatment. Given the hepatotropic nature of systemically administered adenovirus type 2- and 5-derived vectors, it will be essential to monitor liver functions of patients included in all gene therapy trials involving adenoviral vectors with the HSVtk gene.
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PMID:Severe hepatic dysfunction after adenovirus-mediated transfer of the herpes simplex virus thymidine kinase gene and ganciclovir administration. 961 68

Suicide gene therapy based on ganciclovir (GCV) metabolism by transgene herpes simplex thymidine kinase (HSV-1 TK) has been used to selectively kill proliferating cells in clinical settings such as cancer, vascular restenosis, and immunological disorders. We investigated whether encapsulation of ganciclovir (GCV) into liposomes would improve its efficacy, especially against hepatic tumors. Large unilamellar liposomes containing GCV were prepared by reversed-phase evaporation. Pharmacokinetic studies in rats showed that, compared with free GCV, the intravenous injection of liposome-encapsulated GCV (lip-GCV) led to a faster decrease in GCV plasma concentrations, but higher liver-blood ratios. After treatment of syngeneic HSV-1 TK+ liver metastases in rats, histologically active tumors were found in 95% of the transplanted lesions when physiological saline had been given and in 50% when free GCV had been given at 90.2 microM/kg twice daily. This dose is known to be insufficient for the eradication of HSV-1 TK+ tumors. In contrast, only 5% viable tumors were found in rats receiving lip-GCV at this same concentration. Average tumor volumes were 19 +/- 15, 7 +/- 9, and <1 mm3 for the control, free GCV, and lip-GCV groups, respectively. GCV-related toxicity was no longer observed. The results demonstrate that liposomal encapsulation of GCV is feasible and significantly enhances its efficacy against HSV-1 TK+ hepatic tumors.
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PMID:Liposomal encapsulation of ganciclovir enhances the efficacy of herpes simplex virus type 1 thymidine kinase suicide gene therapy against hepatic tumors in rats. 1039 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

Transcriptional targeting of gene expression has been plagued by the weakness of tissue-specific promoters. Thus, to increase promoter strength while maintaining tissue specificity, we constructed a recombinant adenovirus containing a binary promoter system with a tumor-specific promoter (CEA; carcinoembryonic antigen) driving a transcription transactivator, which then activates a minimal promoter to express a suicide gene (HSV-tk; herpes simplex virus thymidine kinase). This ADV/binary-tk induced equal or greater cell killing in a CEA-specific manner in vitro compared with the CEA-independent killing of a vector with a constitutive viral promoter driving HSV-tk (ADV/RSV-tk). To monitor adenovirus-mediated HSV-tk gene expression in vivo, we employed noninvasive nuclear imaging using a radioiodinated nucleoside analog ([((1)31)I]-FIAU) serving as a substrate for HSV-tk. [((1)31)I]-FIAU-derived radioactivity accumulated after intratumoral injection of ADV/binary-tk only in the area of CEA-positive tumors with significantly less spread to the adjacent liver tissue than after administration of the universally expressed ADV/RSV-tk. Both viruses exhibited similar antitumor efficacy upon injection of liver metastases. Importantly, in vivo dose escalation studies demonstrated significantly reduced toxicity after intravenous administration of ADV/binary-tk versus ADV/RSV-tk. In summary, the increased therapeutic index of this novel, amplified CEA-driven suicide gene therapy vector is a proof of principle for the powerful enhancement of a weak tissue-specific promoter for effective tumor restricted gene expression.
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PMID:Tumor-specific transcriptional targeting of suicide gene therapy. 1185 19

Drug resistance is often a limiting factor in successful chemotherapy. Our laboratory has been interested in studying mechanisms of resistance to drugs that are targeted to the thymidylate biosynthesis pathway especially those that target thymidylate synthase (TS) and dihydrofolate reductase (DHFR). We have used leukemia as a model system to study resistance to methotrexate (MTX) and colorectal cancer as the model system to study 5-fluorouracil (5-FU) resistance. In leukemias, we and others have shown that transport, efflux, polyglutamylation and hydrolase activities are major determinants of MTX resistance. We have further reported that some leukemic cells have an increase in DHFR gene copy number possibly contributing to the resistant phenotype. Recently, we have begun to study in detail the molecular mechanisms that govern translational regulation of DHFR in response to MTX as an additional resistance mechanism. Studies thus far involving colorectal tumors obtained from patients have focused predominantly on the predictive value of levels of TS expression and p53 mutations in determining response to 5-FU. Although the predictive value of these two measures appears to be significant, given the variety of resistance to 5-FU observed in cell lines, it is not likely that these are the only measures predictive of response or responsible for acquired resistance to this drug. The enzyme uridine-cytidine monophosphate kinase (UMPK) is an essential and rate-limiting enzyme in 5-FU activation while dihydropyrimidine dehydrogenase (DPD) is a catabolic enzyme that inactivates 5-FU. Alterations in UMPK and DPD may therefore explain failure of 5-FU response in the absence of alterations in TS or p53. Transcription factors that regulate TS may also influence drug sensitivity. We have found that mRNA levels of the E2F family of transcription factors correlates with TS message levels and are higher in lung metastases than in liver metastases of colorectal cancers. Moreover, gene copy number of the E2F-1 gene appears to be increased in a significant number of samples obtained from metastases of colorectal cancer. We have also generated mutants of both DHFR and TS that confer resistance to MTX as well as 5-FU by random as well as site-directed mutagenesis. These mutants used alone or as fusion cDNAs of the mutants have proven to be useful in transplant studies where transfer of these mutant cDNAs to bone marrow cells have been shown to confer drug resistance to recipients. The fusion cDNAs of DHFR such as the DHFR-herpes simplex virus type 1 thymidine kinase (HSVTK) are also useful for regulation of gene expression in vivo using MTX as the small molecule regulator that can be monitored by positron emission tomography (PET) scanning or by optical imaging using a fusion construct such as DHFR-EGFP.
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PMID:Novel aspects of resistance to drugs targeted to dihydrofolate reductase and thymidylate synthase. 1208 58


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