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Toronto, Canada

Chesnelong C.,Foothills Medical Center | Chesnelong C.,Southern Research Institute | Blough M.D.,Foothills Medical Center | Blough M.D.,Southern Research Institute | And 16 more authors.

BackgroundMutations of the isocitrate dehydrogenase 1 and 2 gene (IDH1/2) were initially thought to enhance cancer cell survival and proliferation by promoting the Warburg effect. However, recent experimental data have shown that production of 2-hydroxyglutarate by IDH mutant cells promotes hypoxia-inducible factor (HIF)1α degradation and, by doing so, may have unexpected metabolic effects.MethodsWe used human glioma tissues and derived brain tumor stem cells (BTSCs) to study the expression of HIF1α target genes in IDH mutant ( mt) and IDH wild-type (wt) tumors. Focusing thereafter on the major glycolytic enzyme, lactate dehydrogenase A (LDHA), we used standard molecular methods and pyrosequencing-based DNA methylation analysis to identify mechanisms by which LDHA expression was regulated in human gliomas.ResultsWe found that HIF1α-responsive genes, including many essential for glycolysis (SLC2A1, PDK1, LDHA, SLC16A3), were underexpressed in IDHmt gliomas and/or derived BTSCs. We then demonstrated that LDHA was silenced in IDH mt derived BTSCs, including those that did not retain the mutant IDH1 allele (mIDHwt), matched BTSC xenografts, and parental glioma tissues. Silencing of LDHA was associated with increased methylation of the LDHA promoter, as was ectopic expression of mutant IDH1 in immortalized human astrocytes. Furthermore, in a search of The Cancer Genome Atlas, we found low expression and high methylation of LDHA in IDHmt glioblastomas. ConclusionTo our knowledge, this is the first demonstration of downregulation of LDHA in cancer. Although unexpected findings, silencing of LDHA and downregulation of several other glycolysis essential genes raise the intriguing possibility that IDHmt gliomas have limited glycolytic capacity, which may contribute to their slow growth and better prognosis. © 2013 © The Author(s) 2013. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. Source

We have successfully integrated previously established Intracranial window (ICW) technology (1-4) with intravital 2-photon confocal microscopy to develop a novel platform that allows for direct long-term visualization of tissue structure changes intracranially. Imaging at a single cell resolution in a real-time fashion provides supplementary dynamic information beyond that provided by standard end-point histological analysis, which looks solely at 'snap-shot' cross sections of tissue. Establishing this intravital imaging technique in fluorescent chimeric mice, we are able to image four fluorescent channels simultaneously. By incorporating fluorescently labeled cells, such as GFP+ bone marrow, it is possible to track the fate of these cells studying their long-term migration, integration and differentiation within tissue. Further integration of a secondary reporter cell, such as an mCherry glioma tumor line, allows for characterization of cell:cell interactions. Structural changes in the tissue microenvironment can be highlighted through the addition of intra-vital dyes and antibodies, for example CD31 tagged antibodies and Dextran molecules. Moreover, we describe the combination of our ICW imaging model with a small animal micro-irradiator that provides stereotactic irradiation, creating a platform through which the dynamic tissue changes that occur following the administration of ionizing irradiation can be assessed. Current limitations of our model include penetrance of the microscope, which is limited to a depth of up to 900 μm from the sub cortical surface, limiting imaging to the dorsal axis of the brain. The presence of the skull bone makes the ICW a more challenging technical procedure, compared to the more established and utilized chamber models currently used to study mammary tissue and fat pads (5-7). In addition, the ICW provides many challenges when optimizing the imaging. Source

Jahangiri A.,Brain Tumor Research Center | Aghi M.K.,Brain Tumor Research Center
Biochimica et Biophysica Acta - Reviews on Cancer

No fully validated biological markers currently exist to predict responsiveness to or the development of evasion to anti-angiogenic therapy of cancer. The identification of such biomarkers is vital to move these therapies forward, as failure to respond to these treatments is often associated with rapid tumor progression that could have been averted had the intrinsic or acquired evasion to anti-angiogenic therapy been identified in a timely fashion. Furthermore, the high cost of antiangiogenic therapies makes it important to avoid utilizing them in the setting of lack of response or developing evasion, making the identification of biomarkers even more important. A number of potential physiologic, circulating, tissue, and imaging biomarkers have emerged from recently completed preclinical animal studies and clinical trials. In this review, we define 5 different types of biomarkers (physiologic, circulating, intratumoral, genetic polymorphisms, and radiographic); discuss the challenges in establishing biomarkers of antiangiogenic therapy in animal models and in clinical trials; and discuss future strategies to identify and validate biomarkers of anti-angiogenic therapy. © 2011 Elsevier B.V. Source

Lerner R.G.,Brain Tumor Research Center | Petritsch C.,Brain Tumor Research Center
Nature Cell Biology

Defective asymmetric cell divisions of stem and progenitor cells are associated with tumorigenesis by a largely unknown mechanism. A signalling axis involving Snail, microRNA-146a and Numb is now shown to regulate the switch between symmetric and asymmetric cell division in colorectal cancer stem cells. © 2014 Macmillan Publishers Limited. All rights reserved. Source

Chung C.,University of Toronto | Jalali S.,Brain Tumor Research Center | Foltz W.,University of Toronto | Burrell K.,Brain Tumor Research Center | And 8 more authors.
International Journal of Radiation Oncology Biology Physics

Purpose: There is a growing need for noninvasive biomarkers to guide individualized spatiotemporal delivery of radiation therapy (RT) and antiangiogenic (AA) therapy for brain tumors. This study explored early biomarkers of response to RT and the AA agent sunitinib (SU), in a murine intracranial glioma model, using serial magnetic resonance imaging (MRI). Methods and Materials: Mice with MRI-visible tumors were stratified by tumor size into 4 therapy arms: control, RT, SU, and SU plus RT (SURT). Single-fraction conformal RT was delivered using MRI and on-line cone beam computed tomography (CT) guidance. Serial MR images (T2-weighted, diffusion, dynamic contrast-enhanced and gadolinium-enhanced T1-weighted scans) were acquired biweekly to evaluate tumor volume, apparent diffusion coefficient (ADC), and tumor perfusion and permeability responses (Ktrans, K ep). Results: Mice in all treatment arms survived longer than those in control, with a median survival of 35 days for SURT (P<.0001) and 30 days for RT (P=.009) and SU (P=.01) mice vs 26 days for control mice. At Day 3, ADC rise was greater with RT than without (P=.002). Sunitinib treatment reduced tumor perfusion/permeability values with mean Ktrans reduction of 27.6% for SU (P=.04) and 26.3% for SURT (P=.04) mice and mean Kep reduction of 38.1% for SU (P=.01) and 27.3% for SURT (P=.02) mice. The magnitude of individual mouse ADC responses at Days 3 and 7 correlated with subsequent tumor growth rate R values of -0.878 (P=.002) and -0.80 (P=.01), respectively. Conclusions: Early quantitative changes in diffusion and perfusion MRI measures reflect treatment responses soon after starting therapy and thereby raise the potential for these imaging biomarkers to guide adaptive and potentially individualized therapy approaches in the future. © 2013 Elsevier Inc. All rights reserved. Source

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