Matching Items (8)

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Disarming Olig2: Targeting its partner protein Hdac1

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

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.

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Date Created
  • 2017-05

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The Effects of Human Hairless Gene Overexpression on U87 MG Glioblastoma Cell Function

Description

Glioblastoma multiforme (GBM) is an aggressive malignant brain tumor with a median prognosis of 14 months. Human hairless protein (HR) is a 130 kDa nuclear transcription factor that plays a

Glioblastoma multiforme (GBM) is an aggressive malignant brain tumor with a median prognosis of 14 months. Human hairless protein (HR) is a 130 kDa nuclear transcription factor that plays a critical role in skin and hair function but was found to be highly expressed in neural tissue as well. The expression of HR in GBM tumor cells is significantly decreased compared to the normal brain tissue and low levels of HR expression is associated with shortened patient survival. We have recently reported that HR is a DNA binding phosphoprotein, which binds to p53 protein and p53 responsive element (p53RE) in vitro and in intact cells. We hypothesized that HR can regulate p53 downstream target genes, and consequently affects cellular function and activity. To test the hypothesis, we overexpressed HR in normal human embryonic kidney HEK293 and GBM U87MG cell lines and characterized these cells by analyzing p53 target gene expression, viability, cell-cycle arrest, and apoptosis. The results revealed that the overexpressed HR not only regulates p53-mediated target gene expression, but also significantly inhibit cell viability, induced early apoptosis, and G2/M cell cycle arrest in U87MG cells, compared to mock groups. Translating the knowledge gained from this research on the connections between HR and GBM could aid in identifying novel therapies to circumvent GBM progression or improve clinical outcome.

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Date Created
  • 2018-05

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Differential Relationships Among Autoantibody Responses to P53 Family Proteins in Late Stage Colorectal Cancer

Description

Colorectal cancer (CRC) is one of the most highly diagnosed cancers in the United States and accounts for 9.5% of all new cancer cases worldwide. With a 50% five-year prognosis,

Colorectal cancer (CRC) is one of the most highly diagnosed cancers in the United States and accounts for 9.5% of all new cancer cases worldwide. With a 50% five-year prognosis, it is the second highest cancerous cause of death in the U.S. CRC tumors express antigens that are capable of inducing an immune response. The identification of autoantibodies (AAb) against tumor-associated antigens (TAA) may facilitate personalized tumor treatment in the form of targeted immunotherapy. The objective of this study was to observe the AAb expression raised against a 2000 human gene survey in late-stage colorectal cancer using the Nucleic Acid Programmable Protein Arrays (NAPPA). AAbs from serum samples were collected from 80 patients who died within 24 months of their last blood draw and 80 age and gender matched healthy control were profiled using NAPPA. TAA p53, a well-established protein that is one of the most highly mutated across a variety of cancers, was one of the top candidates based on statistical analysis, which, along with its family proteins p63 and p73 (which showed inverse AAb response profiles) warranted further testing via RAPID ELISA. Statistical analysis from these results revealed an inverse differential relationship between p53 and p63, in which p53 seropositivity was higher in patients than in controls, while the opposite was unexpectedly the case for p63. This study involving the AAb immunoprofiling of advanced stage CRC patients is one of the first to shed light on the high-throughput feasibility of immunoproteomic experiments using protein arrays as well as the identification of immunotherapy targets in a more rapid move towards specialized treatment of advanced CRC.

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Date Created
  • 2014-12

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Understanding the Biochemistry of Different P53 Mutants Having Different Sensitivities to Simvastatin

Description

The p53 gene functions as a tumor suppressor that inhibits proliferation, regulates apoptosis, DNA repair, and normal cell cycle arrest. Mutation of the p53 gene is linked to be prevalent

The p53 gene functions as a tumor suppressor that inhibits proliferation, regulates apoptosis, DNA repair, and normal cell cycle arrest. Mutation of the p53 gene is linked to be prevalent in 50% of all human cancers. In this paper, we are exploring triple negative breast cancer and the effects of simvastatin on tumor growth and survival. Simvastatin is a drug that is primarily used to treat high cholesterol and heart disease. Simvastatin is unique because it is able to inhibit protein prenylation through regulation of the mevalonate pathway. This makes it a potential targeted drug for therapy against p53 mutant cancer. The mechanism behind this is hypothesized to be correlated to aberrant activation of the Ras pathway. The Ras subfamily functions to transcriptionally regulate cell growth and survival, and will therefore allow for a tumor to thrive if the pathway is continually and abnormally activated. The Ras protein has to be prenylated in order for activation of this pathway to occur, making statin drug treatment a viable option as a cancer treatment. This is because it acts as a regulator of the mevalonate pathway which is upstream of protein prenylation. It is thus vital to understand these pathways at both the gene and protein level in different p53 mutants to further understand if simvastatin is indeed a drug with anti-cancer properties and can be used to target cancers with p53 mutation. The goal of this project is to study the biochemistry behind the mutation of p53's sensitivity to statin. With this information we can create a possible signature for those who could benefit from Simvastatin drug treatment as a possible targeted treatment for p53 mutant cancers.

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Date Created
  • 2016-12

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Characterizing p53REs in the Human Hairless Gene Promoter and 5' Untranslated Region

Description

The human hairless gene (HR) encodes a 130 kDa transcription factor that is primarily expressed in the brain and skin. In the promoter and 5'-untranslated regions (5'-UTR) of HR, there

The human hairless gene (HR) encodes a 130 kDa transcription factor that is primarily expressed in the brain and skin. In the promoter and 5'-untranslated regions (5'-UTR) of HR, there are three putative consensus p53 responsive elements (p53RE). p53 is a tumor suppressor protein that regulates cell proliferation, apoptosis, and other cell functions. The p53 protein, a known tumor suppressor, acts as a transcription factor and binds to DNA p53REs to activate or repress transcription of the target gene. In general, the p53 binding sequence is 5'-RRRCWWGYYY-3' where W is A or T, and R and Y are purines or pyrimidines, respectively. However, even if the p53 binding sequence does not match the consensus sequence, p53 protein might still be able to bind to the response element. The intent of this investigation was to identify and characterize the p53REs in the promoter and 5'-UTR of HR. If the three p53REs (p53RE1, p53RE2, and p53RE3) are functional, then p53 can bind there and might regulate HR gene expression. The first aim for this thesis was to clone the putative p53REs into a luciferase reporter and to characterize the transcription of these p53REs in glioblastoma (U87 MG) and human embryonic kidney (HEK293) cell lines. Through the transactivation assay, it was discovered that p53REs 2 and 3 were functional in HEK293, but none of the response elements were functional in U87 MG. Since p53 displayed a different regulatory capacity of HR expression in HEK293 and U87 MG cells, the second aim was to verify whether the p53REs are mutated in GBM U87 MG cells by genomic DNA sequencing.

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Date Created
  • 2018-05

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Migration and invasion study of non-transformed mammary epithelial cells overexpressing TP53 missense mutations frequently occurring in breast cancer

Description

The purpose of this project was to identify proteins associated with the migration and invasion of non-transformed MCF10A mammary epithelial cells with ectopically expressed missense mutations in p53. Because of

The purpose of this project was to identify proteins associated with the migration and invasion of non-transformed MCF10A mammary epithelial cells with ectopically expressed missense mutations in p53. Because of the prevalence of TP53 missense mutations in basal-like and triple-negative breast cancer tumors, understanding the effect of TP53 mutations on the phenotypic expression of human mammary epithelial cells may offer new therapeutic targets for those currently lacking in treatment options. As such, MCF10A mammary epithelial cells ectopically overexpressing structural mutations (G245S, H179R, R175H, Y163C, Y220C, and Y234C) and DNA-binding mutations (R248Q, R248W, R273C, and R273H) in the DNA-binding domain were selected for use in this project. Overexpression of p53 in the mutant cell lines was confirmed by western blot and q-PCR analysis targeting the V5 epitope tag present in the pLenti4 vector used to transduce TP53 into the mutant cell lines. Characterization of the invasion and migration phenotypes resulting from the overexpression of p53 in the mutant cell lines was achieved using transwell invasion and migration assays with Boyden chambers. Statistical analysis showed that three cell lines—DNA-contact mutants R248W and R273C and structural mutant Y220C—were consistently more migratory and invasive and demonstrated a relationship between the migration and invasion properties of the mutant cell lines. Two families of proteins were then explored: those involved in the Epithelial-Mesenchymal Transition (EMT) and matrix metalloproteinases (MMPs). Results of q-PCR and immunofluorescence analysis of epithelial marker E-cadherin and mesenchymal proteins Slug and Vimentin did not show a clear relationship between mRNA and protein expression levels with the migration and invasiveness phenotypes observed in the transwell studies. Results of western blotting, q-PCR, and zymography of MMP-2 and MMP-9 also did not show any consistent results indicating a definite relationship between MMPs and the overall invasiveness of the cells. Finally, two drugs were tested as possible treatments inhibiting invasiveness: ebselen and SBI-183. These drugs were tested on only the most invasive of the MCF10A p53 mutant cell lines (R248W, R273C, and Y220C). Results of invasion assay following 30 μM treatment with ebselen and SBI-183 showed that ebselen does not inhibit invasiveness; SBI-183, however, did inhibit invasiveness in all three cell lines tested. As such, SBI-183 will be an important compound to study in the future as a treatment that could potentially serve to benefit triple-negative or basal-like breast cancer patients who currently lack therapeutic treatment options.

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Date Created
  • 2015-05

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Glioblastoma in the Crosshairs: Development of a Dual Reporter Assay for Discovery of Olig2 Inhibiting Drugs

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.

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.

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Date Created
  • 2014-05

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Genome-driven targeted cancer therapy

Description

Cancer is a heterogeneous disease with discrete oncogenic mechanisms. P53 mutation is the most common oncogenic mutation in many cancers including breast cancer. This dissertation focuses on fundamental genetic alterations

Cancer is a heterogeneous disease with discrete oncogenic mechanisms. P53 mutation is the most common oncogenic mutation in many cancers including breast cancer. This dissertation focuses on fundamental genetic alterations enforced by p53 mutation as an indirect target. p53 mutation upregulates the mevalonate pathway genes altering cholesterol biosynthesis and prenylation. Prenylation, a lipid modification, is required for small GTPases signaling cascades. Project 1 demonstrates that prenylation inhibition can specifically target cells harboring p53 mutation resulting in reduced tumor proliferation and migration. Mutating p53 is associated with Ras and RhoA activation and statin prevents this activity by inhibiting prenylation. Ras-related pathway genes were selected from the transcriptomic analysis for evaluating correlation to statin sensitivity. A gene signature of seventeen genes and TP53 genotype (referred to as MPR signature) is generated to predict response to statins. MPR signature is validated through two datasets of drug screening in cell lines. As advancements in targeted gene modification are rising, the CRISPR-Cas9 technology has emerged as a new cancer therapeutic strategy. One of the important risk factors in gene therapy is the immune recognition of the exogenous therapeutic tool, resulting in obstruction of treatment and possibly serious health consequences. Project 2 describes a method development that can potentially improve the safety and efficacy of gene-targeting proteins. A cohort of 155 healthy individuals was screened for pre-existing B cell and T cell immune response to the S. pyogenes Cas9 protein. We detected antibodies against Cas9 in more than 10% of the healthy population and identified two immunodominant T cell epitopes of this protein. A de-immunized Cas9 that maintains the wild-type functionality was engineered by mutating the identified T cell epitopes. The gene signature and method described here have the potential to improve strategies for genome-driven tumor targeting.

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Created

Date Created
  • 2017