59 research outputs found
Switching on the Lights for Gene Therapy
Strategies for non-invasive and quantitative imaging of gene expression in vivo have been developed over the past decade. Non-invasive assessment of the dynamics of gene regulation is of interest for the detection of endogenous disease-specific biological alterations (e.g., signal transduction) and for monitoring the induction and regulation of therapeutic genes (e.g., gene therapy). To demonstrate that non-invasive imaging of regulated expression of any type of gene after in vivo transduction by versatile vectors is feasible, we generated regulatable herpes simplex virus type 1 (HSV-1) amplicon vectors carrying hormone (mifepristone) or antibiotic (tetracycline) regulated promoters driving the proportional co-expression of two marker genes. Regulated gene expression was monitored by fluorescence microscopy in culture and by positron emission tomography (PET) or bioluminescence (BLI) in vivo. The induction levels evaluated in glioma models varied depending on the dose of inductor. With fluorescence microscopy and BLI being the tools for assessing gene expression in culture and animal models, and with PET being the technology for possible application in humans, the generated vectors may serve to non-invasively monitor the dynamics of any gene of interest which is proportionally co-expressed with the respective imaging marker gene in research applications aiming towards translation into clinical application
Imaging noradrenergic influence on amyloid pathology in mouse models of Alzheimer’s disease
peer reviewedMolecular imaging aims towards the non-invasive characterization of disease-specific molecular alterations in the living organism in vivo. In that, molecular imaging opens a new dimension in our understanding of disease pathogenesis, as it allows the non-invasive determination of the dynamics of changes on the molecular level. IMAGING OF AD CHARACTERISTIC CHANGES BY microPET: The imaging technology being employed includes magnetic resonance imaging (MRI) and nuclear imaging as well as optical-based imaging technologies. These imaging modalities are employed together or alone for disease phenotyping, development of imaging-guided therapeutic strategies and in basic and translational research. In this study, we review recent investigations employing positron emission tomography and MRI for phenotyping mouse models of Alzheimer's disease by imaging. We demonstrate that imaging has an important role in the characterization of mouse models of neurodegenerative diseases
Switching on the Lights for Gene Therapy
Strategies for non-invasive and quantitative imaging of gene expression in vivo have been developed over the past decade. Non-invasive assessment of the dynamics of gene regulation is of interest for the detection of endogenous disease-specific biological alterations (e.g., signal transduction) and for monitoring the induction and regulation of therapeutic genes (e.g., gene therapy). To demonstrate that non-invasive imaging of regulated expression of any type of gene after in vivo transduction by versatile vectors is feasible, we generated regulatable herpes simplex virus type 1 (HSV-1) amplicon vectors carrying hormone (mifepristone) or antibiotic (tetracycline) regulated promoters driving the proportional co-expression of two marker genes. Regulated gene expression was monitored by fluorescence microscopy in culture and by positron emission tomography (PET) or bioluminescence (BLI) in vivo. The induction levels evaluated in glioma models varied depending on the dose of inductor. With fluorescence microscopy and BLI being the tools for assessing gene expression in culture and animal models, and with PET being the technology for possible application in humans, the generated vectors may serve to non-invasively monitor the dynamics of any gene of interest which is proportionally co-expressed with the respective imaging marker gene in research applications aiming towards translation into clinical application
REGIO- AND STEREOSPECIFIC SYNTHESIS OF 7-DEAZAPURINE 2'-DEOXYRIBONUCLEOSIDES AND INCORPORATION OF NUCLEOSIDE ISOSTERES INTO OLIGONUCLEOTIDES
2'-Deoxytubercidin and 7-deaza-2'-deoxyguanosine, isosteres of the
parent nucleosides 2'-deoxyadenosine and 2'-deoxyguanosine have been
synthesized via phase-transfer glycosylation of appropriately protected
pyrrolo[2,3-d]pyrimidines with 1-chloro-2-deoxy-3 ,5-di-O-p-toluoy1-Derythro-
pentofuranose via a regio- and stereospecific route. The nuclecside
isosteres were provided with suitable protecting groups and converted
into their O-3'-phosphoramidites. Application of these compounds
in solid-support oligonucleotide synthesis yielded self-complementary
oligomers with alternating d(TuT) or d(c’Gc) sequences. Additionally
the incorporation of the 7-deazapurine 2'-deoxyribofuranosides into the
Eco RI sequence was accomplished. Applying phosphite triester condensation
in solution, (2',5')- and (3',5')-tubercidylyl-tubercidins were
synthesized
Molecular Imaging of Gliomas
Gliomas are the most common types of brain tumors. Although sophisticated regimens of conventional therapies are being carried out to treat patients with gliomas, the disease invariably leads to death over months or years. Before new and potentially more effective treatment strategies, such as gene- and cell-based therapies, can be effectively implemented in the clinical application, certain prerequisites have to be established. First of all, the exact localization, extent, and metabolic activity of the glioma must be determined to identify the biologically active target tissue for a biological treatment regimen; this is usually performed by imaging the expression of up-regulated endogenous genes coding for glucose or amino acid transporters and cellular hexokinase and thymidine kinase genes, respectively. Second, neuronal function and functional changes within the surrounding brain tissue have to be assessed in order to save this tissue from therapy-induced damage. Third, pathognomonic genetic changes leading to disease have to be explored on the molecular level to serve as specific targets for patient-tailored therapies. Last, a concerted noninvasive analysis of both endogenous and exogenous gene expression in animal models as well as the clinical setting is desirable to effectively translate new treatment strategies from experimental into clinical application. All of these issues can be addressed by multimodal radionuclide and magnetic resonance imaging techniques and fall into the exciting and fast growing field of molecular and functional imaging. Noninvasive imaging of endogenous gene expression by means of positron emission tomography (PET) may reveal insight into the molecular basis of pathogenesis and metabolic activity of the glioma and the extent of treatment response. When exogenous genes are introduced to serve for a therapeutic function, PET imaging may reveal the assessment of the “location,” “magnitude,” and “duration” of therapeutic gene expression and its relation to the therapeutic effect. Detailed reviews on molecular imaging have been published from the perspective of radionuclide imaging (Gambhir et al., 2000; Blasberg and Tjuvajev, 2002) as well as magnetic resonance and optical imaging (Weissleder, 2002). The present review focuses on molecular imaging of gliomas with special reference on the status and perspectives of imaging of endogenous and exogenously introduced gene expression in order to develop improved diagnostics and more effective treatment strategies of gliomas and, in that, to eventually improve the grim prognosis of this devastating disease
Normal brain cells contribute to the bystander effect in suicide gene therapy of malignant glioma
Copyright © 2007 by the American Association for Cancer Researc
Imaging-guided gene therapy of experimental gliomas
To further develop gene therapy for patients with glioblastomas, an experimental gene therapy protocol was established comprising a series of imaging parameters for (i) noninvasive assessment of viable target tissue followed by (ii) targeted application of herpes simplex virus type 1 (HSV-1) amplicon vectors and (iii) quantification of treatment effects by imaging. We show that viable target tissue amenable for application of gene therapy vectors can be identified by multitracer positron emission tomography (PET) using 2-18F-fluoro-2- deoxy-D-glucose, methyl-11C-L-methionine, or 3¶-deoxy-3¶-18Ffluoro- L-thymidine ([18F]FLT). Targeted application of HSV-1
amplicon vectors containing two therapeutic genes with
synergistic antitumor activity (Escherichia coli cytosine
deaminase, cd, and mutated HSV-1 thymidine kinase, tk39,
fused to green fluorescent protein gene, gfp) leads to an
overall response rate of 68%, with 18% complete responses
and 50% partial responses. Most importantly, we show that
the ‘‘tissue dose’’ of HSV-1 amplicon vector–mediated gene
expression can be noninvasively assessed by -[4-18F-fluoro-3- (hydroxymethyl)butyl]guanine ([18F]FHBG) PET. Therapeutic effects could be monitored by PET with significant differences in [18F]FLT accumulation in all positive control tumors and 72% in vivo transduced tumors (P = 0.01) as early as 4 days after prodrug therapy. For all stably and in vivo transduced tumors, cdIREStk39gfp gene expression as measured by [18F]FHBG-PET correlated with therapeutic efficiency as measured by [18F]FLT-PET. These data indicate that imagingguided vector application with determination of tissue dose of vector-mediated gene expression and correlation to induced therapeutic effect using multimodal imaging is feasible.
This strategy will help in the development of safe and efficient gene therapy protocols for clinical application
- …