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Ionic Mechanism Of Lysosomal Function And Cell Metabolism, Jian Xiong

Dissertations & Theses (Open Access)

Two Pore Channels (TPCs) are endolysosomal ion channels that are permeable to sodium and calcium. Defects in TPCs have been implicated to impair vesicle trafficking, autophagy and cell metabolism control; however, the detailed mechanism remains largely unknown. In this study, I show that TPCs are critical for appropriate cargo delivery to the lysosomes and deletion of either TPC1 or TPC2 leads to delayed clearance of autophagosomes, resulting in enlarged lysosomes and accumulated contents inside the lysosomes. Cells with both TPC deleted also exhibit 50% reduction in lysosomal amino acids under normal culture conditions, leading to reduced homeostatic mTORC1 activation.

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Mechanisms Underlying The Sensitivity And Resistance Of Gastric Cancer Cells To Met Inhibitors, Rebecca Schroeder

Dissertations & Theses (Open Access)

MET amplification has been clinically credentialed as a therapeutic target in gastric cancer, but the molecular mechanisms underlying sensitivity and resistance to MET inhibitors are still not well understood. Using whole-genome mRNA expression profiling, we identified autophagy as a top molecular pathway that was activated by the MET inhibitor crizotinib in drug-sensitive human gastric cancer cells, and functional studies confirmed that crizotinib increased autophagy levels in the drug sensitive cells in a concentration-dependent manner. We then used chemical and molecular approaches to inhibit autophagy in order to define its role in cell death. The clinically available inhibitor of autophagy, chloroquine, …

Targeting Autophagy To Improve Efficacy Of Cdk4/6 Inhibition In Breast Cancer, Smruthi Vijayaraghavan

Dissertations & Theses (Open Access)

Deregulation of the cell cycle machinery is a hallmark of cancer, leading to aberrant proliferation and tumorigenesis. The crucial role of the CDK4/6-Cyclin D pathway has led to the development and FDA approval (palbociclib, ribociclib) of CDK4/6 inhibitors for the treatment of advanced estrogen receptor positive breast cancer. However, three major clinical challenges remain: i) adverse events leading to discontinuation of therapy and ii) lack of reliable biomarkers to identify responsive patients and iii) acquired resistance to CDK4/6 inhibitors. Previous in vitro studies have shown that palbociclib mediated CDK4/6 inhibition induces G1 arrest and senescence in ER+ breast cancer cells, …

The Role Of The Diras Family Members In Regulating Ras Function, Cancer Growth And Autophagy, Margie Nicole Sutton

Dissertations & Theses (Open Access)

DIRAS3 is a maternally imprinted tumor suppressor gene that is downregulated by multiple mechanisms across several tumor types. When re-expressed, DIRAS3 decreases proliferation, inhibits motility, and induces autophagy and tumor dormancy. DIRAS3 encodes a 26 kDa small GTPase with 60% homology to Ras and Rap, differing from oncogenic Ras family members by a 34-amino acid N-terminal extension that is required for its tumor suppressive function in ovarian cancer. By assessing the structure-function relationship, I found that DIRAS3 inhibits Ras-induced transformation and is a natural antagonist of Ras/MAPK signaling. DIRAS3 binds directly to Ras and disrupts cluster formation inhibiting the activation …

The Role Of Autophagy In The Sensitivity Of Osteosarcoma Cells To Gemcitabine Treatment, Janice M. Santiago-O'Farrill

Dissertations & Theses (Open Access)

Despite treatment improvement for osteosarcoma (OS), overall survival has remained unchanged in the last 20 years. Pulmonary metastasis continues to be the main cause of death; novel therapeutic strategies are urgently needed to improve the survival rate of these patients. Previous data in our laboratory has demonstrated that aerosol gemcitabine (GCB) treatment has a significant therapeutic effect on metastatic OS. However, treatment efficacy is decreased due to acquired resistance by a population of tumor cells that fails to respond to treatment. Recent studies have implicated autophagy as a resistance mechanism in various types of cancer. The purpose of this study …

The Role Of Mir-34a In Inhibition Of Prostate Tumor Growth In The Bone And Induction Of Autophagy, Sanchaika Gaur

Dissertations & Theses (Open Access)

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men in the United States, with most deaths occurring from bone metastasis. Several new therapies have been FDA approved for bone-metastatic PCa, but patient survival has only marginally improved due to therapy resistance, which often arises from constitutive activation of compensatory signaling pathways. This dissertation work focused on a mechanistic understanding of how cross talk between tyrosine kinase receptors contributes to therapy resistance, and how this may be overcome by downregulating expression of these receptors. In PCa cell lines and xenograft models, I demonstrated that activation of IGF-1R …

Strategies To Sensitize Bladder Cancer Cells To Small Molecule Inhibitors Targeting The Pi3k Pathway, Giovanni Nitti

Dissertations & Theses (Open Access)

After many years of cancer research, it is well accepted by the scientific community that the future cure for this disease lies in a personalized therapeutic approach. Anticipating therapeutic outcome based on the genetic signature of a tumor has become the new paradigm. The PI3K pathway represents an ideal target for bladder cancer, as many of the key proteins of this pathway are altered or mutated in this particular type of cancer. Several small molecule inhibitors have been developed to target this pathway, but their efficacy has been shown to be heterogeneous among different cell lines and mostly cytostatic but …

C-Jun N-Terminal Kinases Regulate Adenovirus-Mediated Autophagy And Antigen Presentation, Sarah R. Klein

Dissertations & Theses (Open Access)

Targeted immunotherapy with recombinant, oncolytic adenoviruses is under investigation for the treatment of cancer. Evidence indicates adenoviruses induce autophagy that is required for oncolysis, but the molecular regulation of autophagy in infected cells remains under investigation. Our data suggested the canonical pathway regulating starvation-induced autophagy was not implemented in adenovirus-induced autophagy; however, adenovirus infection triggered phosphorylation of c-Jun N-terminal kinases (JNK) that was essential for autophagy. Adenoviral replication within the host cell elicited JNK pathway activation leading to B cell lymphoma-2 (Bcl-2) phosphorylation. JNK-dependent Bcl-2 phosphorylation stimulated the dissociation of Bcl-2/beclin 1 heterodimers, enabling beclin 1 to initiate autophagy. Moreover, …

Targeting Histone Deacetylases (Hdac) For The Treatment Of Soft Tissue Sarcoma, Gonzalo Lopez

Dissertations & Theses (Open Access)

Targeting Histone deacetylases (HDAC) for the treatment of genetically complex soft tissue sarcoma

Histone deactylase inhibitors (HDACi) are a new class of anticancer therapeutics; however, little is known about HDACi or the individual contribution of HDAC isoform activity in soft tissue sarcoma (STS). We investigated the potential efficacy of HDACi as monotherapy and in combination with chemotherapy in a panel of genetically complex STS. We found that HDACi combined with chemotherapy significantly induced anti-STS effects in vitro and in vivo. We then focused our study of HDACi in malignant peripheral nerve sheath tumor (MPNST), a subtype of highly aggressive, …

Mechanisms Of Adenovirus-Mediated Autophagy, Erin White

Dissertations & Theses (Open Access)

A patient diagnosed with a glioma, generally, has an average of 14 months year to live after implementation of conventional therapies such as surgery, chemotherapy, and radiation. Glioblastomas are highly lethal because of their aggressive nature and resistance to conventional therapies and apoptosis. Thus other avenues of cell death urgently need to be explored. Autophagy, which is also known as programmed cell death type II, has recently been identified as an alternative mechanism to kill apoptosis- resistant cancer cells. Traditionally, researchers have studied how cells undergo autophagy during viral infection as an immune response mechanism, but recently researchers have discovered …

Atm Signaling To Tsc2: Mechanisms And Implications For Cancer Therapy, Angela Alexander

Dissertations & Theses (Open Access)

Ataxia telangiectasia mutated (ATM) is a critical component of the cellular response to DNA damage, where it acts as a damage sensor, and signals to a large network of proteins which execute the important tasks involved in responding to the damage, namely inducing cell cycle checkpoints, inducing DNA repair, modulating transcriptional responses, and regulating cell death pathways if the damage cannot be repaired faithfully. We have now discovered that an additional novel component of this ATM-dependent damage response involves induction of autophagy in response to oxidative stress. In contrast to DNA damage-induced ATM activation however, oxidative stress induced ATM, occurs …