Matching Items (4)
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- All Subjects: Glioblastoma
- Creators: Mehta, Shwetal
Description
A coincidence reporter construct, consisting of the p21-promoter and two luciferase genes (Firefly and Renilla), was constructed for the screening of drugs that might inhibit Olig2's tumorigenic role in glioblastoma. The reporter construct was tested using an Olig2 inhibitor, HSP990, as well as short hairpin RNA targeting Olig2. Further confirmatory analysis is needed before the reporter cell line is ready for high-throughput screening at the NIH and lead compound selection.
ContributorsCusimano, Joseph Michael (Author) / LaBaer, Joshua (Thesis director) / Mangone, Marco (Committee member) / Mehta, Shwetal (Committee member) / Barrett, The Honors College (Contributor) / Department of Chemistry and Biochemistry (Contributor)
Created2014-05
Description
Glioblastoma is the most aggressive and lethal brain tumor, due to its resistance to current conventional therapy. The resistance to chemo- and radiotherapy has been attributed to a special population of cells known as glioma stem cells. Previous literature has shown the importance of a Central Nervous System-restricted transcription factor OLIG2 in maintaining the tumor-propagating potential of these glioma stem cells. OLIG2's function was further elucidated, with its pro-mitogenic function due to its ability to negatively regulate the p53 pathway by suppressing the acetylation of the p53 protein's C terminal domain. Past work in our lab has confirmed that one of OLIG2's partner proteins is Histone Deacetylase 1 (HDAC1). In vitro experiments have also shown that targeting HDAC1 using hairpin RNA in glioma stem cells negatively impacts proliferation. In a survival study using a murine glioma model, targeting Hdac1 using hairpin RNA is shown to reduce tumor burden and increase survival. In this paper, we demonstrate that silencing Hdac1 expression reduces proliferation, increases cell death, likely a result of increased acetylation of p53. Olig2 expression levels seem to be unaffected in GSCs, demonstrating that the Hdac1 protein ablation is indeed lethal to GSCs. This work builds upon previously collected results, confirming that Hdac1 is a potential surrogate target for Olig2's pro-mitotic function in regulating the p53 pathway.
ContributorsLoo, Vincent You Wei (Author) / LaBaer, Joshua (Thesis director) / Mehta, Shwetal (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Glioblastoma Multiforme (GBM) is a grade IV astrocytoma and the most aggressive form of cancer that begins within the brain. The two-year average survival rate of GBM in the United States of America is 25%, and it has a higher incidence in individuals within the ages of 45 - 60 years. GBM Tumor formation can either begin as normal brain cells or develop from an existing low-grade astrocytoma and are housed by the perivascular niche in the brain microenvironment. This niche allows for the persistence of a population of cells known as glioma stem cells (GSC) by supplying optimum growth conditions that build chemoresistance and cause recurrence of the tumor within two to five years of treatment. It has therefore become imperative to understand the role of the perivascular niche on GSCs through in vitro modelling in order to improve the efficiency of therapeutic treatment and increase the survival rate of patients with GBM.
In this study, a unique three dimensional (3D) microfluidic platform that permitted the study of intercellular interactions between three different cell types in the perivascular niche of the brain was developed and utilized for the first time. Specifically, human endothelial cells were embedded in a fibrin matrix and introduced into the vascular layer of the microfluidic platform.
After spontaneous formation of a vascular layer, Normal Human Astrocytes and Patient derived GSC were embedded in a Matrigel® matrix and incorporated in the stroma and tumor regions of the microfluidic device respectively.
Using the established platform, migration, proliferation and stemness of GSCs studies were conducted. The findings obtained indicate that astrocytes in the perivascular niche significantly increase the migratory and proliferative properties of GSCs in the tumor microenvironment, consistent with previous in vivo findings.
The novel GBM tumor microenvironment developed herein, could be utilized for further
in-depth cellular and molecular level studies to dissect the influence of individual factors within the tumor niche on GSCs biology, and could serve as a model for developing targeted therapies.
In this study, a unique three dimensional (3D) microfluidic platform that permitted the study of intercellular interactions between three different cell types in the perivascular niche of the brain was developed and utilized for the first time. Specifically, human endothelial cells were embedded in a fibrin matrix and introduced into the vascular layer of the microfluidic platform.
After spontaneous formation of a vascular layer, Normal Human Astrocytes and Patient derived GSC were embedded in a Matrigel® matrix and incorporated in the stroma and tumor regions of the microfluidic device respectively.
Using the established platform, migration, proliferation and stemness of GSCs studies were conducted. The findings obtained indicate that astrocytes in the perivascular niche significantly increase the migratory and proliferative properties of GSCs in the tumor microenvironment, consistent with previous in vivo findings.
The novel GBM tumor microenvironment developed herein, could be utilized for further
in-depth cellular and molecular level studies to dissect the influence of individual factors within the tumor niche on GSCs biology, and could serve as a model for developing targeted therapies.
ContributorsAdjei-Sowah, Emmanuella Akweley (Author) / Nikkhah, Mehdi (Thesis advisor) / Plaisier, Christopher (Committee member) / Mehta, Shwetal (Committee member) / Arizona State University (Publisher)
Created2020
Description
Glioblastoma (GBM), the most common and aggressive primary brain tumor affecting adults, is characterized by an aberrant yet druggable epigenetic landscape. The Histone Deacetylases (HDACs), a major family of epigenetic regulators, favor transcriptional repression by mediating chromatin compaction and are frequently overexpressed in human cancers, including GBM. Hence, over the last decade there has been considerable interest in using HDAC inhibitors (HDACi) for the treatment of malignant primary brain tumors. However, to date most HDACi tested in clinical trials have failed to provide significant therapeutic benefit to patients with GBM. This is because current HDACi have poor or unknown pharmacokinetic profiles, lack selectivity towards the different HDAC isoforms, and have narrow therapeutic windows. Isoform selectivity for HDACi is important given that broad inhibition of all HDACs results in widespread toxicity across different organs. Moreover, the functional roles of individual HDAC isoforms in GBM are still not well understood. Here, I demonstrate that HDAC1 expression increases with brain tumor grade and is correlated with decreased survival in GBM. I find that HDAC1 is the essential HDAC isoform in glioma stem cells and its loss is not compensated for by its paralogue HDAC2 or other members of the HDAC family. Loss of HDAC1 alone has profound effects on the glioma stem cell phenotype in a p53-dependent manner and leads to significant suppression of tumor growth in vivo. While no HDAC isoform-selective inhibitors are currently available, the second-generation HDACi quisinostat harbors high specificity for HDAC1. I show that quisinostat exhibits potent growth inhibition in multiple patient-derived glioma stem cells. Using a pharmacokinetics- and pharmacodynamics-driven approach, I demonstrate that quisinostat is a brain-penetrant molecule that reduces tumor burden in flank and orthotopic models of GBM and significantly extends survival both alone and in combination with radiotherapy. The work presented in this thesis thereby unveils the non-redundant functions of HDAC1 in therapy- resistant glioma stem cells and identifies a brain-penetrant HDACi with higher selectivity towards HDAC1 as a potent radiosensitizer in preclinical models of GBM. Together, these results provide a rationale for developing quisinostat as a potential adjuvant therapy for the treatment of GBM.
ContributorsLo Cascio, Costanza (Author) / LaBaer, Joshua (Thesis advisor) / Mehta, Shwetal (Committee member) / Mirzadeh, Zaman (Committee member) / Mangone, Marco (Committee member) / Paek, Andrew (Committee member) / Arizona State University (Publisher)
Created2022