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P53 Dimers Elicit Unique Tumor Suppressive Activities Through An Altered Metabolic Program, Jovanka Gencel-Augusto

Dissertations & Theses (Open Access)

p53 is the most frequently mutated tumor suppressor in human cancer. As a tetrameric transcription factor, mutation of the p53 Tetramerization Domain (TD) is a mechanism by which cancers abrogate wild-type (WT) p53 function. p53 TD mutations result in a protein that preferentially forms monomers or dimers. These are also normal p53 states under basal cellular conditions. Although it is accepted that tetrameric p53 is required for full tumor suppressive activities, the physiological relevance of monomeric and dimeric states of p53 is not well understood. We have established in vivo models for monomeric and dimeric p53 which model Li-Fraumeni Syndrome …

Unique Transcriptional Profiles Underlie Osteosarcomagenesis Driven By Different P53 Mutants, Dhruv Chachad

Dissertations & Theses (Open Access)

Missense mutations in the DNA binding domain of the Trp53 gene are characterized as structural (p53R172H) or contact (p53R245W) mutations based on their effect on the conformation of the protein. These mutations show gain-of-function activities such as increased metastatic incidence as compared to p53 loss, often mediated by their interaction with a repertoire of transcription factors. These interactions are largely context specific. In order to understand the mechanisms by which these mutations drive osteosarcoma progression, we created a mouse model, wherein either the p53 structural mutant p53R172H, or the contact mutant, p53R245W, are expressed specifically in …

An Investigation Of Epigenetic Mechanisms Driving The Biology Of Head And Neck Squamous Cell Carcinoma, Scot Carson Callahan

Dissertations & Theses (Open Access)

Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer worldwide and is associated with significant morbidity and mortality. To date, the majority of work in the field has focused on genomic alterations such as mutations and copy number alterations. However, the clinical success of targeted therapies that exploit known genomic alterations, such as EGFR mutations, has remained mixed. Over the past decade, the importance of epigenetic regulators has come to the forefront, with the realization that many of these genes are mutated in cancer. Despite this realization, the role of epigenetics in regulating tumorigenesis, progression and …

P53 Drives A Transcriptional Program That Elicits A Non-Cell-Autonomous Response And Alters Cell State In Vivo, Sydney Moyer

Dissertations & Theses (Open Access)

Cell stress and DNA damage activate the tumor suppressor p53, triggering transcriptional activation of a myriad of target genes. The molecular, morphological, and physiological consequences of this activation remain poorly understood in vivo. We activated a p53 transcriptional program in mice by deletion of Mdm2, a gene which encodes the major p53 inhibitor. By overlaying tissue-specific RNA-sequencing data from pancreas, small intestine, ovary, kidney, and heart with existing p53 ChIP-sequencing, we identified a large repertoire of tissue-specific p53 genes and a common p53 transcriptional signature of seven genes which included Mdm2 but not p21. Global p53 activation …

P53r245w Mutation Elicits Metastatic Phenotype In Pten Deficient Prostate Cancer, Ky Pham

Dissertations & Theses (Open Access)

Trp53 mutations are the most frequent genetic alterations in prostate cancer and are associated with more aggressive disease and worse overall survival. The majority of Trp53 mutations in prostate cancer are missense mutations, resulting in amino acid substitutions with profound effect. In addition to the loss of wild type function, missense mutations in Trp53 result in a gain-of-function (GOF) phenotype. This GOF phenotype confers biologic advantages to the tumor cells, enabling them to metastasize and invade distant organs. In this study, we generated mice carrying a conditional prostate-specific p53R245W mutant and Pten deletion to access the role of this common …

Trim24 As An Oncogene In The Mammary Gland, Aundrietta Duncan

Dissertations & Theses (Open Access)

Despite the many advances made in breast cancer research and treatments, breast cancer remains one of the deadliest diseases plaguing women worldwide. While many findings on genetic mutations and their role in predisposing people to breast cancer have been uncovered, we are just beginning to understand the extent to which epigenetic regulators promote tumorigenic phenotypes, metastasis, and chemotherapeutic resistance. Moreover, new experimental tools offer the ability to address questions we were previously unable to assess. My project takes advantage of a new mouse model to understand the role of a proto-oncogenic, transcriptional co-regulator, TRIM24, in mammary gland development and disease. …

Phosphorylation Impairs Dicer1 Function To Accelerate Aging And Tumorigenesis In Vivo, Neeraj Aryal

Dissertations & Theses (Open Access)

Altered DICER1 protein levels are associated with developmental disorders, infertility, macular degenerative blindness, aging, and cancer in humans. Recently, post-translational regulation of Dicer1 via phosphorylation has been described in C. elegans. Oscillation of Dicer1 phosphorylation to regulate its activity is essential for germ cell development and embryogenesis in worms. These observations led us to posit that Dicer1 protein levels and activity are under tight regulation for normal mammalian homeostasis. To test whether phosphorylation of Dicer1 regulates its activity in mammals, I generated phospho-mimetic knock-in mouse models by replacing Serines 1712 and 1836 with Aspartic acids individually or together (dual …

Targeting Apoptotic Pathways To Overcome Drug Resistance In Acute Myeloid Leukemia, Rongqing Pan

Dissertations & Theses (Open Access)

Evasion of apoptosis is integral to tumorigenesis and drug resistance. BCL-2 and p53 proteins represent two focal nodes in convergent apoptosis signaling. Upregulation of anti-apoptotic BCL-2 family members and inactivation of p53 functions are two canonical approaches exploited by cancer cells to escape apoptosis. In the current study, we find that BCL-2 protein is highly expressed in acute myeloid leukemia (AML) cells. BCL-2–specific inhibitor ABT-199 potently induces mitochondrial apoptosis in AML cells and effectively kills AML stem/progenitor cells. Our biomarker studies demonstrate that both BH3 profiling and the expression profiling of BCL-2 proteins may serve as predictive biomarkers for the …

Using Mouse Models To Define How The P53 R72p Polymorphism Impacts The Adverse Effects Of Doxorubicin And Ionizing Radiation, Emily Dominguez

Dissertations & Theses (Open Access)

The single nucleotide polymorphism (SNP) at codon 72 of the tumor suppressor gene p53 codes for either an arginine (R) or proline (P) (p53 R72P). This SNP may impact how cells respond to genotoxic insult. Studies in cell culture and in tissues from mouse models of the SNP indicate that, in response to gentoxic treatment, the two variants may differentially induce apoptosis and expression of p53 target genes. In epidemiological studies, the P variant is associated with decreased cancer survival and increased risk of side-effects from genotoxic cancer treatment. Genotoxic therapy is still the mainstay of cancer treatment, and doxorubicin …

Investigating The Roles Of Δnp63 As A Suppressor Of Migration, Invasion, And Metastasis, Ramon E. Flores Gonzalez

Dissertations & Theses (Open Access)

Cancer is one of the leading causes of death and disease in the world. Considerable resources are spent to study and understand cancer, with the hope of developing new treatments and eventually cures that will help millions of people. Efforts to understand cancer are hindered by its inherent complexity and instability. Nonetheless, understanding the basics of tumor development and progression are the key to focused on studying the role of ΔNp63 in cancer, a p53 family member known to be involved in epithelial development, microRNA biogenesis, and stem cell maintenance. Using the strength of in vivo mouse models, we found …

Circumventing Cisplatin Resistance In Ovarian Cancers Through Reactivation Of P53 By Non-Cross-Resistant Platinum Analogs, Michelle Martinez-Rivera

Dissertations & Theses (Open Access)

Abstract

CIRCUMVENTING CISPLATIN RESISTANCE IN OVARIAN CANCERS THROUGH REACTIVATION OF P53 BY NON-CROSS-RESISTANT PLATINUM ANALOGS

Michelle Martinez-Rivera, B.S.

Advisory Professor: Zahid H. Siddik, Ph.D.

Cisplatin (cis-Pt), an anticancer platinum (Pt) drug, is used widely in the treatment of several malignancies, such as ovarian cancer. This Pt compound induces DNA damage, which results in p53 activation through post-translational modifications, mainly phosphorylation, culminating in execution of programmed cell-death. However, despite initial therapeutic response to cis-Pt, clinical resistance to this drug emerges leading to disease progression. Pt-resistance phenotypes have been associated with dysfunction in the p53 signaling pathway. Therefore, an effort to understand …

The Role Of Gdf15 In Ovarian Cancer, Daisy I. Izaguirre

Dissertations & Theses (Open Access)

Growth Differentiation Factor 15 (GDF15) is induced in situations such as stress, inflammation, treatment with non-steroidal anti-inflammatory drugs, as well as other therapeutic agents. As a secreted protein, GDF15 is seen as a potential biomarker in several types of cancer as well as in other diseases such as cardiovascular diseases, diabetes, and rheumatoid arthritis. In ovarian cancer, high GDF15 serum levels correspond to poor survival. It has further been shown to be expressed at higher levels in serum in ovarian cancer patients post-chemotherapy than pre-chemotherapy.

The overall 5-year survival for ovarian cancer is 46%, as a result of late diagnosis …

Investigating Checkpoint Kinases 1/2 As Novel Therapeutic Targets In Head And Neck Squamous Cell Carcinoma, Mayur Arvind Gadhikar

Dissertations & Theses (Open Access)

Cisplatin, despite being the cornerstone chemotherapy for the treatment of head and neck squamous cell carcinoma (HNSCC), provides clinical benefits in just a subset of patients. This together with the lack of biomarkers predicting therapeutic responses, have led to unacceptably high rate of treatment failures in HNSCC. TP53 is the most frequently mutated gene in HNSCC, and the effect of p53 loss or mutation on cisplatin responses in HNSCC is poorly understood. In the current study, we hypothesized that HNSCC cells respond to cisplatin in a p53 dependent manner and unambiguously show that presence of wild-type TP53 (wtp53) confers sensitivity …

Reactive Oxygen Species And P21 Waf1/Cip1 Are Both Essential For, Alison Fitzgerald

Dissertations & Theses (Open Access)

Treatment of Head and Neck Squamous Cell Carcinoma, HNSCC, often requires multimodal therapy, including radiation therapy. The efficacy of radiotherapy in controlling locoregional recurrence, the most frequent cause of death from HNSCC, is critically important for patient survival. One potential biomarker to determine radioresistance is TP53, whose alterations are predictive of poor radiation response. The following work shows that the p53 transcriptional target, p21, is crucial in initiating and maintaining senescence in HNSCC, through its ability to regulate reactive oxygen species (ROS). With the use of a novel system to evaluate the impact of the TP53 missense mutations, we …

Targeting The Mdm2-P53 Axis For The Treatment Of Dedifferentiated Liposarcoma, Katelynn Bill

Dissertations & Theses (Open Access)

Dedifferentiated liposarcoma (DDLPS) is an aggressive malignancy characterized by a high rate of recurrence and dismal patient outcome. Minimal improvement in patient survival has been made in the last several decades, highlighting the crucial need for improved therapeutic strategies. A better understanding of the molecular deregulations underlying DDLPS would facilitate the discovery of improved therapeutic approaches. MDM2 is a well characterized oncoprotein and the most known negative regulator of p53. MDM2 amplification is considered the “hallmark” of DDLPS. Additionally, these tumors are known to harbor wild-type p53. We sought to take advantage of this knowledge and evaluate the role of …

Brit1/Mcph1 Mediates The Dna Damage Response By Inducing P53 Stability And Promoting Atr Signaling, Edward Wang

Dissertations & Theses (Open Access)

The BRCT-repeat inhibitor of hTERT (BRIT1)/MCPH1 protein promotes the process of homologous recombination (HR) to repair DNA double strand breaks (DSBs). In response to DSBs, BRIT1 foci form at damaged sites, and recruits downstream repair proteins including 53BP1, MDC1, NBS1, and the SWI/SNF complex to the DSB region to promote DNA repair. BRIT1 copy number deficiency correlates with increased genomic instability in ovarian cancer specimens and breast cancer cell lines. Here, we propose that additional functions of BRIT1 include a direct interaction with the p53 tumor suppressor protein to promote p53 stability, and binding and recruitment of TopBP1 to sites …

P53 Maintains Hepatic Cell Identity During Liver Regeneration, Zeynep Hande Coban Akdemir

Dissertations & Theses (Open Access)

p53 MAINTAINS HEPATIC CELL IDENTITY DURING LIVER REGENERATION

Zeynep Hande Coban Akdemir, B.S.,M.A.

Advisory Professor: Michelle Craig Barton, Ph.D.

p53 is a tumor suppressor that has been well studied in tumor-derived, cultured cells. However, its functions in normal proliferating cells and tissues are generally overlooked. We propose that p53 functions during the G1-S transition can be studied in normal, differentiated cells during surgery-induced liver regeneration. Two-thirds partial hepatectomy (PH) of mouse liver offers a unique model to compare p53 functions in regenerating versus sham (control) cells. My hypothesis is that intersection of global expression analyses (microarray and RNA sequencing) and …

Therapeutic Efficacy Of P53 Restoration In Mdm2-Overexpressing Tumors, Qin Li

Dissertations & Theses (Open Access)

The TP53 tumor suppressor is the most mutated gene in human cancers. Recent studies using genetically modified mouse models have shown that restoring the expression of wild-type p53 has led to tumor growth suppression in various types of tumors lacking p53. Other mechanisms, e.g. upregulation of Mdm2 levels, exist in tumors to inactivate the p53 pathway. Mdm2, an E3 ubiquitin-ligase that targets p53 for proteasomal degradation, is present at high levels in many tumors with wild-type p53. In this study, we probed the effects of restoring p53 activity in Mdm2-overexpressing tumors genetically using animal models. Here we demonstrated high levels …

Genome-Wide Profiling Unveils Criticial Functions Of P53 In Human Embryonic Stem Cells, Kadir C. Akdemir

Dissertations & Theses (Open Access)

Embryonic stem cells (ESCs) possess two unique characteristics: infinite self-renewal and the potential to differentiate into almost every cell type (pluripotency). Recently, global expression analyses of metastatic breast and lung cancers revealed an ESC-like expression program or signature, specifically for cancers that are mutant for p53 function. Surprisingly, although p53 is widely recognized as the guardian of the genome, due to its roles in cell cycle checkpoints, programmed cell death or senescence, relatively little is known about p53 functions in normal cells, especially in ESCs. My hypothesis is that p53 has specific transcription regulatory functions in human ESCs (hESCs) that …

A Study On The Function Of 14-3-3sigma In Regulating Cancer Energy Metabolism, Liem M. Phan, Liem M. Phan

Dissertations & Theses (Open Access)

Metabolic reprogramming has been shown to be a major cancer hallmark providing tumor cells with significant advantages for survival, proliferation, growth, metastasis and resistance against anti-cancer therapies. Glycolysis, glutaminolysis and mitochondrial biogenesis are among the most essential cancer metabolic alterations because these pathways provide cancer cells with not only energy but also crucial metabolites to support large-scale biosynthesis, rapid proliferation and tumorigenesis. In this study, we find that 14-3-3σ suppresses all these three metabolic processes by promoting the degradation of their main driver, c-Myc. In fact, 14-3-3s significantly enhances c-Myc poly-ubiquitination and subsequent degradation, reduces c-Myc transcriptional activity, and down-regulates …

14-3-3 Zeta Overexpression Serves As A Novel Molecular Switch Turning Tgf-Beta From Tumor Suppressor To Tumor Promoter, Jia Xu

Dissertations & Theses (Open Access)

TGF-β plays an important role in differentiation and tissue morphogenesis as well as cancer progression. However, the role of TGF-β in cancer is complicate. TGF-β has primarily been recognized as tumor suppressor, because it can directly inhibit cell proliferation of normal and premalignant epithelial cell. However, in the last stage of tumor progression, TGF-β functions as tumor promoter to enhance tumor cells metastatic dissemination and expands metastatic colonies. Currently, the mechanism of how TGF-β switches its role from tumor suppressor to promoter still remains elusive. Here we identify that overexpression of 14-3-3ζ inhibits TGF-β’s cell cytostatic program through destabilizing p53 …

Function Of Znf668 In Cancer Development, Ruozhen Hu

Dissertations & Theses (Open Access)

Human cancer develops as a result of accumulation of mutations in oncogenes and tumor suppressor genes. Zinc finger protein 668 (ZNF668) has recently been identified and validated as one of the highly mutated genes in breast cancer, but its function is entirely unknown. Here, we report two major functions of ZNF668 in cancer development.

(1) ZNF668 functions as a tumor suppressor by regulating p53 protein stability and function. We demonstrate that ZNF668 is a nucleolar protein that physically interacts with both MDM2 and p53. By binding to MDM2, ZNF668 regulates MDM2 autoubiquitination and prevents MDM2-mediated p53 ubiquitination and degradation; ZNF668 …

Dissecting The Interaction Between P53 And Trim24, Aundrietta D. Duncan

Dissertations & Theses (Open Access)

Dissecting the Interaction of p53 and TRIM24

Aundrietta DeVan Duncan

Supervisory Professor, Michelle Barton, Ph.D.

p53, the “guardian of the genome”, plays an important role in multiple biological processes including cell cycle, angiogenesis, DNA repair and apoptosis. Because it is mutated in over 50% of cancers, p53 has been widely studied in established cancer cell lines. However, little is known about the function of p53 in a normal cell. We focused on characterizing p53 in normal cells and during differentiation. Our lab recently identified a novel binding partner of p53, Tripartite Motif 24 protein (TRIM24). TRIM24 is a member of …

Upregulation Of Reactive Oxygen Species During The Retrovirus Life Cycle And Their Roles In A Mutant Of Moloney Murine Leukemia Virus, Ts1-Mediated Neurodegeneration, Soo Jin Kim

Dissertations & Theses (Open Access)

Viral invasion of the central nervous system (CNS) and development of neurological symptoms is a characteristic of many retroviruses. The mechanism by which retrovirus infection causes neurological dysfunction has yet to be fully elucidated. Given the complexity of the retrovirus-mediated neuropathogenesis, studies using small animal models are extremely valuable. Our laboratory has used a mutant moloney murine leukemia retrovirus, ts1-mediated neurodegneration. We hypothesize that astrocytes play an important role in ts1-induced neurodegeneration since they are retroviral reservoirs and supporting cells for neurons. It has been shown that ts1 is able to infect astrocytes in vivo and in …

A Novel Function For Aurora B Kinase In The Regulation Of P53 By Phosphorylation, Chris P. Gully

Dissertations & Theses (Open Access)

The mitotic kinase Aurora B plays a pivotal role in mitosis and cytokinesis and governs the spindle assembly checkpoint which ensures correct chromosome segregation and normal progression through mitosis. Aurora B is overexpressed in breast and other cancers and may be an important molecular target for chemotherapy. Tumor suppressor p53 is the guardian of the genome and an important negative regulator of the cell cycle. Previously, it was unknown whether Aurora B and p53 had mutual regulation during the cell cycle. A small molecule specific inhibitor of Aurora B, AZD1152, gave us an indication that Aurora B negatively impacted p53 …

14-3-3sigma Negatively Regulates The Stability And Subcellular Localization Of Cop1, Chun-Hui Su

Dissertations & Theses (Open Access)

Mammalian constitutive photomorphogenic 1 (COP1), a p53 E3 ubiquitin ligase, is a key negative regulator for p53. DNA damage leads to the translocation of COP1 to the cytoplasm, but the underlying mechanism remains unknown. We discovered that 14-3-3σ controlled COP1 subcellular localization and protein stability. Investigation of the underlying mechanism suggested that, upon DNA damage, 14-3-3σ bound to phosphorylated COP1 at S387, resulting in COP1 translocation to the cytoplasm and cytoplasmic COP1 ubiquitination and proteasomal degradation. 14-3-3σ targeted COP1 for degradation to prevent COP1-mediated p53 degradation, p53 ubiquitination, and p53 transcription repression. COP1 expression promoted cell proliferation, cell transformation, and …

New Target Genes For Tumor Suppressors P53 And P73 In Regenerating Liver, Svitlana M. Kurinna

Dissertations & Theses (Open Access)

The p53-family of proteins regulates expression of target genes during tissue development and differentiation. Within the p53-family, p53 and p73 have hepatic-specific functions in development and tumor suppression. Despite a growing list of p53/p73 target genes, very few of these have been studied in vivo, and the knowledge regarding functions of p53 and p73 in normal tissues remains limited. p53+/-p73+/- mice develop hepatocellular carcinoma (HCC), whereas overexpression of p53 in human HCC leads to tumor regression. However, the mechanism of p53/p73 function in liver remains poorly characterized. Here, the model of mouse liver regeneration is used to identify new target …

The Consequences Of Disrupting The Mdm2-P53 Balance In Hematopoiesis, Hussein A. Abbas

Dissertations & Theses (Open Access)

The bone marrow accommodates hematopoietic stem cells and progenitors. These cells provide an indispensible resource for replenishing the blood constituents throughout an organism’s life. A tissue with such a high turn-over rate mandates intact cycling checkpoint and apoptotic pathways to avoid inappropriate cell proliferation and ultimately the development of leukemias. p53, a major tumor suppressor, is a transcription factor that regulates cell cycle, and induces apoptosis and senescence. Mice inheriting a hypomorphic p53 allele in the absence of Mdm2, a p53 inhibitor, have elevated p53 cell cycle activity and die by postnatal day 13 due to hematopoietic failure. Hematopoiesis progresses …