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 expression of connexin43, the primary gap-junction constituent of glial cells, was evaluated at the messenger RNA and protein levels in different grades of astrocytoma to investigate the relevance of gap junctions in herpes simplex virus-thymidine kinase (HSV-tk)-mediated gene therapy of brain tumors. Transduction of the retroviral-mediated HSV-tk gene into tumor cells with subsequent administration of ganciclovir has recently been used as an experimental therapeutic strategy for treatment of brain tumors. One aspect of this approach is the bystander effect, which augments the efficacy of this therapeutic approach. Glioblastoma cells with minimum levels of connexin43 protein were transfected with a connexin43 complementary DNA. These cells manifested a marked increase in the in vitro bystander effect, supporting the contention that the in vitro bystander effect is a consequence of metabolic cooperation between cells mediated by gap junctions. To assess relative levels of gap-junction protein expression in the relevant tumor type, we examined primary astrocytomas, primary astrocytoma cell cultures, and glioblastoma cell lines. Although most astrocytoma tumor samples expressed connexin43, they differed in the level of expression, with the greatest variation exhibited in high-grade astrocytomas. Primary glioblastoma cell cultures and established glioblastoma cell lines also displayed some variability in connexin43 levels. In aggregate, our results anticipate that glioblastomas will have a varied bystander effect during HSV-tk gene therapy depending on the level of connexin43 expression.
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PMID:Protein and messenger RNA expression of connexin43 in astrocytomas: implications in brain tumor gene therapy. 862 59

Glioblastoma is a very aggressive astrocytic tumor and most patients have 1-year survival time after diagnosis. A promising therapeutic strategy is the local delivery of the herpes simplex virus thymidine kinase gene in the tumor bed followed by ganciclovir treatment. The presence of functional gap junctions is highly relevant for the success of suicide gene therapy. Connexins are expressed in practically all tissues and form gap junctions that allow intercellular communication. Connexin 43 (Cx43) is the major connexin member being expressed in astrocytes but its status in glioblastoma is not well defined. We have investigated by immunofluorescence the presence of Cx43 in 74 human glioblastoma samples; its expression was detected in 77% of the samples analyzed. We report here that glioblastoma is a heterogenous disease as regards Cx43 expression with presentations, in which Cx43 expression is unaltered, reduced or totally lost. A predominant Cx43 cytoplasmic localization was observed in four out of eight primary glioblastoma cultures that we have established. This aberrant localization reduced gap junctionnal intercellular communication by 50 to 75% as compared with primary cell cultures displaying gap junctional plaques. However, the bystander effect evaluated after lentiviral delivery of the herpes simplex virus thymidine kinase gene and ganciclovir treatment was detected in all Cx43-positive primary cell cultures, and it was independant of the Cx43 localization. These findings may have important clinical implications for the design of anticancer cytotoxic therapies that rely on the gap junction-mediated bystander effect for their success.
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PMID:Gap junctions in human glioblastomas: implications for suicide gene therapy. 2177 29

Glioblastoma is a highly aggressive malignant tumor involving glial cells in the human brain. We used high-throughput sequencing to comprehensively profile the small RNAs expressed in glioblastoma and non-tumor brain tissues. MicroRNAs (miRNAs) made up the large majority of small RNAs, and we identified over 400 different cellular pre-miRNAs. No known viral miRNAs were detected in any of the samples analyzed. Cluster analysis revealed several miRNAs that were significantly down-regulated in glioblastomas, including miR-128, miR-124, miR-7, miR-139, miR-95, and miR-873. Post-transcriptional editing was observed for several miRNAs, including the miR-376 family, miR-411, miR-381, and miR-379. Using the deep sequencing information, we designed a lentiviral vector expressing a cell suicide gene, the herpes simplex virus thymidine kinase (HSV-TK) gene, under the regulation of a miRNA, miR-128, that was found to be enriched in non-tumor brain tissue yet down-regulated in glioblastomas, Glioblastoma cells transduced with this vector were selectively killed when cultured in the presence of ganciclovir. Using an in vitro model to recapitulate expression of brain-enriched miRNAs, we demonstrated that neuronally differentiated SH-SY5Y cells transduced with the miRNA-regulated HSV-TK vector are protected from killing by expression of endogenous miR-128. Together, these results provide an in-depth analysis of miRNA dysregulation in glioblastoma and demonstrate the potential utility of these data in the design of miRNA-regulated therapies for the treatment of brain cancers.
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PMID:Reduced expression of brain-enriched microRNAs in glioblastomas permits targeted regulation of a cell death gene. 2191 81

Genetically modified adipose tissue derived mesenchymal stromal cells (hAMSCs) with tumor homing capacity have been proposed for localized therapy of chemo- and radiotherapy resistant glioblastomas. We demonstrate an effective procedure to optimize glioblastoma therapy based on the use of genetically modified hAMSCs and in vivo non invasive monitoring of tumor and therapeutic cells. Glioblastoma U87 cells expressing Photinus pyralis luciferase (Pluc) were implanted in combination with hAMSCs expressing a trifunctional Renilla reniformis luciferase-red fluorescent protein-thymidine kinase reporter in the brains of SCID mice that were subsequently treated with ganciclovir (GCV). The resulting optimized therapy was effective and monitoring of tumor cells by bioluminescence imaging (BLI) showed that after 49 days GCV treatment reduced significantly the hAMSC treated tumors; by a factor of 10(4) relative to controls. Using a Pluc reporter regulated by an endothelial specific promoter and in vivo BLI to image hAMSC differentiation we gained insight on the therapeutic mechanism. Implanted hAMSCs homed to tumor vessels, where they differentiated to endothelial cells. We propose that the tumor killing efficiency of genetically modified hAMSCs results from their association with the tumor vascular system and should be useful vehicles to deliver localized therapy to glioblastoma surgical borders following tumor resection.
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PMID:Glioblastoma therapy with cytotoxic mesenchymal stromal cells optimized by bioluminescence imaging of tumor and therapeutic cell response. 2252 83

Glioblastoma is the most malignant form of brain tumor. In this study, combination therapy with temozolomide (TMZ) and the herpes simplex virus thymidine kinase (HSVtk) gene was evaluated in glioblastoma models. The R7L10 peptide was used as a carrier of TMZ and the HSVtk gene. TMZ was loaded into R7L10 micelles using the oil-in-water emulsion/solvent evaporation method. The TMZ-loaded R7L10 (R7L10-TMZ) micelles formed a complex with the HSVtk gene, pHSVtk. The formation of the R7L10-TMZ/pHSVtk complex was confirmed by gel retardation and heparin competition assays. An in vitro transfection assay demonstrated that the transfection efficiency of R7L10-TMZ was similar to that of R7L10 in C6 glioblastoma cells. R7L10-TMZ had greater anti-tumor effects than TMZ alone in C6 cells in vitro, suggesting that R7L10 is an efficient carrier of TMZ. The in vivo efficacy of the R7L10-TMZ/pHSVtk complex was evaluated in the intracranial glioblastoma model. HSVtk expression in tumors was confirmed by immunohistochemistry. Furthermore, a greater anti-tumor effect was observed in the R7L10-TMZ/pHSVtk group compared with the TMZ or R7L10/pHSVtk single injection group. In conclusion, combined delivery of TMZ and the HSVtk gene using R7L10 peptides may be useful for the treatment of glioblastoma.
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PMID:Combined delivery of temozolomide and the thymidine kinase gene for treatment of glioblastoma. 2740 51

Glioblastoma is the most common malignant brain cancer in adults, with poor prognosis. The blood-brain barrier limits the arrival of several promising anti-glioblastoma drugs, and restricts the design of efficient therapies. Recently, by using state-of-the-art technologies, including thymidine kinase targeting system in combination with glioblastoma xenograft mouse models, it was revealed that targeting glioblastoma-derived pericytes improves chemotherapy efficiency. Strikingly, ibrutinib treatment enhances chemotherapeutic effectiveness, by targeting pericytes, improving blood-brain barrier permeability, and prolonging survival. This study identifies glioblastoma-derived pericyte as a novel target in the brain tumor microenvironment during carcinogenesis. Here, we summarize and evaluate recent advances in the understanding of pericyte's role in the glioblastoma microenvironment.
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PMID:Targeting glioblastoma-derived pericytes improves chemotherapeutic outcome. 2976 Dec 49

Glioblastoma persists as a uniformly deadly diagnosis for patients and effective therapeutic options are gravely needed. Recently, targeted gene therapy approaches are reemerging as attractive experimental clinical agents. Our ligand-directed hybrid virus of adeno-associated virus and phage (AAVP) is a targeted gene delivery vector that has been used in several formulations displaying targeting ligand peptides to deliver clinically applicable transgenes. Here we compared different constructs side-by-side in a tumor model, an orthotopic model of xenograft human glioblastoma cells stereotactically implanted in immunodeficient mice. We have used divergent therapeutic strategies for two AAVP constructs, both displaying a double-cyclic RGD4C motif ligand specific for alpha V integrins expressed in tumor vascular endothelium, but carrying different genes of interest for the treatment of intracranial xenografted tumors. One construct delivered tumor necrosis factor (TNF), a purely cytotoxic gene for antitumor activity (RGD4C-AAVP-TNF); in the other construct, we delivered Herpes simplex virus thymidine kinase (HSVtk) for in tandem molecular-genetic imaging and targeted therapy (RGD4C-AAVP-HSVtk) utilizing ganciclovir (GCV) for a suicide gene therapy. Both AAVP constructs demonstrated antitumor activity, with damage to the tumor-associated neovasculature and induction of cell death evident after treatment. In addition, the ability to monitor transgene expression with a radiolabeled HSVtk substrate pre and post GCV treatment demonstrated the theranostic potential of RGD4C-AAVP-HSVtk. We conclude that targeted AAVP constructs delivering either cytotoxic TNF or theranostic HSVtk followed by suicide gene therapy with GCV have comparable preclinical efficacy, at least in this standard experimental model. The results presented here provide a blueprint for future studies of targeted gene delivery against human glioblastomas and other brain tumors.
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PMID:Targeted AAVP-based therapy in a mouse model of human glioblastoma: a comparison of cytotoxic versus suicide gene delivery strategies. 3113 Jul 31

Glioblastoma are highly invasive and associated with limited therapeutic options and a grim prognosis. Using stem cells to extend current therapeutic strategies by targeted drug delivery to infiltrated tumors cells is highly attractive. This study analyzes the tumor homing and therapeutic abilities of clinical grade human mesenchymal stem cells (MSCs) in an orthotopic glioblastoma mouse model. Our time course analysis demonstrated that MSCs display a rapid targeted migration to intracerebral U87 glioma xenografts growing in the contralateral hemisphere within the first 48h hours after application as assessed by histology and 7T magnetic resonance imaging. MSCs accumulated predominantly peritumorally but also infiltrated the main tumor mass and targeted distant tumor satellites while no MSCs were found in other regions of the brain. Intratumoral application of MSCs expressing herpes simplex virus thymidine kinase followed by systemic prodrug application of ganciclovir led to a significant tumor growth inhibition of 86% versus the control groups (p<0.05), which translated in a significant prolonged survival time (p<0.05). This study demonstrates that human MSCs generated according to apceth's GMP process from healthy donors are able to target and provide a significant growth inhibition in a glioblastoma model supporting a potential clinical translation.
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PMID:Preclinical analysis of human mesenchymal stem cells: tumor tropism and therapeutic efficiency of local HSV-TK suicide gene therapy in glioblastoma. 3169 82

Glioblastoma is the most aggressive brain tumor characterized by diffuse infiltration into the normal brain parenchyma. Neural stem cells are known to possess the tumor-tropic migratory capacity and thus can be used as cellular vehicles for targeted delivery of therapeutic agents. In the present study, we evaluated the efficacy of herpes simplex virus thymidine kinase (HSV-TK) suicide gene therapy for glioblastoma using neural stem/progenitor cells (NS/PCs) derived from human induced pluripotent stem cells (hiPSCs). Although transduction of hiPSCs is preferable for a safe and stable supply in the clinical setting, high-level and/or constitutive HSV-TK expression was highly cytotoxic to hiPSCs. To overcome this problem, we used the tetracycline-inducible system to control the expression of HSV-TK. hiPSC-derived NS/PCs expressing HSV-TK were transplanted in an orthotopic xenograft mouse model of human glioblastoma. Glioblastoma cell growth in mice was dramatically inhibited following ganciclovir (GCV) administration. Survival of the mice was significantly prolonged with administration of GCV compared with control groups. Time-lapse imaging of organotypic brain slice cultures first demonstrated the directional migration of NS/PCs toward glioblastoma cells and the bystander killing effect upon GCV treatment. hiPSC-derived NS/PCs with HSV-TK/GCV suicide gene system may have considerable therapeutic potential for the treatment of glioblastoma. Color images are available online.
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PMID:Gene Therapy Using Neural Stem/Progenitor Cells Derived from Human Induced Pluripotent Stem Cells: Visualization of Migration and Bystander Killing Effect. 3207 24

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