Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Kaposi's sarcoma (KS) is a major AIDS-related malignancy associated with significant morbidity and mortality. Current chemotherapeutic regimens are associated with a dismal prognosis. In an effort to develop a new approach to KS treatment, we devised a gene therapy-based adenovirus retargeting schema that redirects the adenovirus to fibroblast growth factor receptors endogenously present on the cell surface of KS cells. By using a bifunctional conjugate consisting of a blocking antiadenoviral knob Fab linked to basic fibroblast growth factor, FGF2, the gene transduction of KS cells was enhanced 7.7-44 fold; recombinant adenoviruses encoding either the firefly luciferase reporter gene, or the herpes simplex thymidine kinase gene, demonstrated quantitative enhancement of expression in the KS cell lines. In this regard, two KS cell lines that were previously refractory to native adenovirus transduction could be successfully transduced by the addition of the conjugate. This study thus addresses the utility of adenoviral retargeting to the FGF receptor in KS cells that are ordinarily transduction refractory to standardized approaches and allows practical development of gene therapy approaches for the treatment of human KS.
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PMID:Targeted gene delivery to Kaposi's sarcoma cells via the fibroblast growth factor receptor. 910 44

A number of preclinical and human clinical gene therapy trials using adenoviral vectors have shown that the number of viral particles necessary to give adequate levels of gene transfer can be associated with significant vector-related toxicity. In an effort to reduce the number of adenoviral particles required for a given level of gene transfer, we sought to redirect adenoviral infection via a receptor that is highly expressed on the target cells. By using basic fibroblast growth factor (FGF2) as the targeting ligand, adenovirus-mediated gene transfer to the human ovarian cancer cell line SKOV3.ip1 was significantly enhanced, permitting the transduction of a greater number of target cells to be achieved by a given dose of virus. In a murine model of human ovarian carcinoma, an FGF2-redirected adenoviral vector carrying the gene for herpes simplex virus thymidine kinase (AdCMVHSV-TK) was shown to result in a significant prolongation of survival compared with the same number of particles of unmodified AdCMVHSV-TK. In addition, equivalent survival rates were achieved with a 10-fold lower dose of the FGF2-redirected AdCMVHSV-TK compared with the unmodified vector. To our knowledge, this is the first report demonstrating that strategies to enhance the efficiency of in vivo transduction of adenoviral vectors will be of clinical utility.
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PMID:Basic fibroblast growth factor enhancement of adenovirus-mediated delivery of the herpes simplex virus thymidine kinase gene results in augmented therapeutic benefit in a murine model of ovarian cancer. 979 78

Nonviral DNA delivery strategies for gene therapy have generally been limited by a lack of specificity and efficacy. However, ligand-mediated endocytosis can specifically deliver DNA in vitro to cells bearing the appropriate cognate receptors. Similarly, in order to circumvent problems related to efficacy, DNA must encode proteins with high intrinsic activities. We show here that the ligand basic fibroblast growth factor (FGF2) can target FGF receptor-bearing cells with DNA encoding therapeutic proteins. Delivery of genes encoding saporin, a highly potent ribosomal inactivating protein, or the conditionally cytotoxic herpes simplex virus thymidine kinase, a protein that can kill cells by activating the prodrug ganciclovir, is demonstrated. The saporin gene was codon optimized for mammalian expression and demonstrated to express functional protein in a cell-free assay. FGF2-mediated delivery of saporin DNA or thymidine kinase DNA followed by ganciclovir treatment resulted in a 60 and 75% decrease in cell number, respectively. Specificity of gene delivery was demonstrated in competition assays with free FGF2 or with recombinant soluble FGF receptor. Alternatively, when histone H1, a ligand that binds to cell surface heparan sulfate proteoglycans ("low-affinity" FGF receptors), was used to deliver DNA encoding thymidine kinase, no ganciclovir sensitivity was observed. These findings establish the feasibility of using ligands such as FGF2 to specifically deliver genes encoding molecular chemotherapeutic agents to cells.
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PMID:Targeted delivery of DNA encoding cytotoxic proteins through high-affinity fibroblast growth factor receptors. 985 23

Adenovirus (Ad) have been used as vectors to deliver genes to a wide variety of tissues. Despite achieving high expression levels in vivo, Ad vectors display normal tissue toxicity, transient expression, and antivector immune responses that limit therapeutic potential. To circumvent these problems, several retargeting strategies to abrogate native tropism and redirect Ad uptake through defined receptors have been attempted. Despite success in cell culture, in vivo results have generally not shown sufficient selectivity for target tissues. We have previously identified (C. K. Goldman et al., Cancer Res., 57: 1447-1451, 1997) the fibroblast growth factor (FGF) ligand and receptor families as conferring sufficient specificity and binding affinity to be useful for targeting DNA in vivo. In the present studies, we retargeted Ad using basic FGF (FGF2) as a targeting ligand. Cellular uptake is redirected through high-affinity FGF receptors (FGFRs) and not the more ubiquitous lower-affinity Ad receptors. Initial in vitro experiments demonstrated a 10- to 100-fold increase in gene expression in numerous FGFR positive (FGFR+) cell lines using FGF2-Ad when compared with Ad. To determine whether increased selectivity could be detected in vivo, FGF2-Ad was administered i.v. to normal mice. FGF2-Ad demonstrates markedly decreased hepatic toxicity and liver transgene expression compared with Ad treatment. Importantly, FGF2-Ad encoding the herpes simplex virus thymidine kinase (TK) gene transduces Ad-resistant FGFR+ tumor cells both ex vivo and in vivo, which results in substantially enhanced survival (180-260%) when the prodrug ganciclovir is administered. Because FGFRs are up-regulated on many types of malignant or injured cells, this broadly useful method to redirect native Ad tropism and to increase the potency of gene expression may offer significant therapeutic advantages.
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PMID:Fibroblast growth factor 2 retargeted adenovirus has redirected cellular tropism: evidence for reduced toxicity and enhanced antitumor activity in mice. 1036 82

Targeted vectors provide a number of advantages for systemic and local gene delivery strategies. Several groups have investigated the utility of using various ligands to alter the tropism of adenovirus (Ad) vectors. We have previously demonstrated that fibroblast growth factor (FGF) ligands can specifically target DNA transfection and Ad transduction through high-affinity FGF receptors (FGFRs). FGFRs are overexpressed in abnormally proliferating tissues, such as malignancies. The present studies explore the effects of retargeting with FGF2 on the tissue localization pattern and the systemic toxicity of Ad in mice. Results of semiquantitative PCR analyses indicate that the distribution of FGF2-Ad vector genome sequences after intravenous administration in mice is altered. Markedly lower amounts (10- to 20-fold) of FGF2-Ad localize to the liver when compared with native Ad. This decrease in liver deposition translates into a significant reduction in subsequent toxicity as measured by serum transaminases and histopathology in mice injected with FGF2-AdHSV-thymidine kinase with and without ganciclovir administration. In an intraperitoneal model of ovarian cancer, FGF2-Ad generates increased transgene expression in tumor tissue when compared with Ad. Taken together, these results indicate that the retargeting of Ad with FGF2 results in a more efficient vector system for systemic and regional gene therapy applications, with concomitant lower levels of systemic toxicity.
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PMID:Fibroblast growth factor 2-retargeted adenoviral vectors exhibit a modified biolocalization pattern and display reduced toxicity relative to native adenoviral vectors. 1064 50

Pancreatic ductal adenocarcinomas (PDACs) overexpress various cell-surface tyrosine kinase receptors, including the type I high-affinity fibroblast growth factor receptor (FGFR-1). The purpose of this study was to determine whether FGFR-targeted gene therapy is feasible in this disorder. Accordingly, the effects of a conjugate consisting of fibroblast growth factor (FGF)-2 linked to a Fab' fragment against the adenovirus knob region were evaluated in human pancreatic cancer cell lines treated with an adenoviral vector containing the herpes simplex virus thymidine kinase (AdTK) gene. An adenoviral vector containing the firefly luciferase reporter gene (AdLuc) served to assess infection efficiency, and was initially tested in L6 rat myoblasts. In parental L6 cells that express exceedingly low levels of high-affinity FGFRs, transduction with AdLuc was enhanced 7- to 10-fold with the FGF2-Fab' conjugate, whereas in L6 cells transfected to express FGFR-1, it was enhanced 39- to 52-fold. The pancreatic cancer cell lines expressed variable levels of the four high-affinity FGF receptors, and exhibited 2- to 34-fold increases in gene transduction in the presence of the FGF2-Fab' conjugate. In the absence of FGF2-Fab' there was no correlation between surface binding of FGF2 and AdLuc transduction efficiency, whereas in the presence of FGF2-Fab', enhanced AdLuc transduction efficiency correlated with greater surface binding of FGF2. In the absence of AdTK, all the cell lines were insensitive to ganciclovir, whereas after AdTK transduction, only ASPC-1 and PANC-1 cells were resistant to ganciclovir even in the presence of FGF2-Fab'. Ganciclovir-mediated inhibition was dependent on the conjugate in CAPAN-1 and COLO-357 cells, but was independent of the conjugate in T3M4 and MIA-PaCa-2 cells. Real-time quantitative PCR of laser-captured cancer cells revealed high levels of various FGFR mRNA species in six of seven PDAC tumor samples. These findings indicate that transduction efficiency with FGF2-Fab' in pancreatic cancer cells is independent of native adenoviral transduction efficiency and is greatest in cells that exhibit concomitant expression of various high-affinity FGFRs. In view of the overexpression of high-affinity FGFRs in the cancer cells in PDAC, our findings also suggest that the combined use of AdTK, ganciclovir, and FGF2-Fab' may ultimately be a promising therapeutic approach in a subgroup of patients with PDAC.
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PMID:Targeting of suicide gene delivery in pancreatic cancer cells via FGF receptors. 1203 63