Doctor of Philosophy, The Ohio State University, 2024, Biomedical Sciences

The cellular and microenvironment contexts are critical for tumorigenesis and are influenced by inherited germline variants. Germline variants can affect the incidence of somatic mutations that confer advantages for uncontrolled tumorigenic growth. Moreover, a somatic mutation alone is not a guarantee of cancer, and the conditions dictated by germline variants can also influence whether or not a mutated cell progresses to cancer. This interaction between germline genetics and somatic mutations (GxM) has been observed though mutation signatures, tumor-immune interactions, and allele-specific imbalance, among other examples. By unknown mechanisms, somatic mutation frequency in cancer differs by ancestry. Patients of African Ancestry (AfA) are more likely to have KRAS mutations in colorectal cancer (CRC) compared to patients of European Ancestry (EuA). Similarly, AfA women are more likely to have TP53 mutations in breast cancer (BC) and to have the more aggressive triple-negative (TNBC) tumor subtype compared to EuA women; Conversely, EuA women are more likely to have PIK3CA mutations in BC compared to AfA women. While social determinants of health (SDOH) and longstanding systematic racism are drivers of many cancer healthcare disparities, the drivers of the observed differences in tumor phenotypes and somatic mutations by ancestry remain unclear. To identify associations between germline variants and KRAS mutations in CRC, we conducted a 2-step association analysis in Chapter 2. We first performed a genome-wide discovery analysis in 7,071 CRC patients of EuA and compared germline genomic data of individuals who had tumors with KRAS mutations to individuals who had KRAS-wildtype (WT) tumors. At the discovery stage, no associated variants were significant at a genome-wide level (P value < 5 x 10-8). Three single nucleotide variants (SNVs) associated with KRAS mutation status with P values < 1x10-6 and 50 with P values < 1x10-5. Of these 50 SNVs, 21 met criteria fo (open full item for complete abstract)

Committee: Amanda Tolland (Advisor); Jing Wang (Committee Member); Sameek Roychowdhury (Committee Member); Christin Burd (Committee Member) Subjects: Genetics; Health Sciences; Molecular Biology

Doctor of Philosophy, The Ohio State University, 2021, Comparative and Veterinary Medicine

Therapeutic estrogens address multiple facets of non-alcoholic steatohepatitis (NASH) pathophysiology. Their potential, however, is limited by undesirable side effects caused by persistent estrogen receptor a (ERa) activation. Estrogen receptor b (ERb) is functionally unique, capable of inducing estrogen's benefits while limiting ERa-mediated side effects. We hypothesized that OSU-ERb-12, a novel carborane selective estrogen receptor modulator with affinity for ERb, would demonstrate therapeutic benefit in preclinical NASH models at doses absent of ERa-mediated effects (ERb-selective). Our objectives were first to describe OSU-ERb-12's drug-like properties by characterizing its ERb-selectivity, pursuing early but critical preclinical safety studies, describing its pharmacokinetic properties, and finally by identifying ERb-selective doses to apply to future studies. We then assessed OSU-ERb-12's therapeutic potential in two pre-clinical models of relevant NASH pathophysiology while simultaneously gaining mechanistic insight into drug efficacy. We applied several in vitro techniques to demonstrate OSU-ERb-12's drug-like properties. We established its ERb-selectivity first through a competitive radioligand-binding assay to demonstrate ligand affinity for ERb, then through a luciferase reporter assay to assess its preferential activation of ERb-mediated transcription. In both experiments, OSU-ERb-12 demonstrated selective properties comparable to LY500307, another ERb-selective agonist. We then put OSU-ERb-12 through nuclear hormone receptor and CYP-inhibition assays to identify potential off-target effects and drug-drug interactions, respectively; none were found suggesting compound safety. Multi-species microsomal stability assays and in vivo pharmacokinetic studies not only demonstrated remarkable OSU-ERb-12 stability in most species, but that the drug has superior pharmacokinetic properties to LY500307. Finally, to establish in vivo ERb-selective doses, we utiliz (open full item for complete abstract)

Committee: Christopher Coss (Advisor); Heather Shive (Committee Member); Moray Campbell (Committee Member); Steven Clinton (Advisor) Subjects: Endocrinology; Medicine; Oncology; Pharmaceuticals; Pharmacology

MS, University of Cincinnati, 2017, Medicine: Molecular and Developmental Biology

Breast cancer is the second leading cause of cancer-related death among women in the United States. Approximately 70% of the patients are classified as estrogen receptor positive (ER+), where the activation of ER by its ligand, estrogen and subsequently the target genes drive tumor progression and survival. In such cases, the treatment to control disease progression is endocrine therapies targeting the activity of ER. Despite the efficacy, 30-40% of patients develop metastasis breast cancer through de novo or acquired resistance. Various novel therapeutic agents have been developed to address this clinical challenge, including the use of cell cycle inhibitors targeting the cyclin-dependent kinases 4 and 6 (CDK4/6) to improve responses and the durability of treatment of ER+ metastatic breast cancer. Acquired mutations in the estrogen receptor alpha (ERa) gene (ESR1) which confer constitutive activity of ERα, were found to be prevalent in ER+ metastatic breast cancer patients with resistance to aromatase inhibitor (AI) therapy. This study evaluated the impact of ESR1 mutations on fulvestrant, the current standard of care of ER+ breast cancer, and several clinically investigated CDK4/6 inhibitors such as palbociclib, abemaciclib and ribociclib. We developed and characterized the growth of in vitro models of ER+ breast cancer carrying several ESR1 mutations in T-47D cells. Stable cell lines were generated for this study using transfection of mutant ERα plasmids and CRISPR technology to induce ESR1 mutation knock-ins. The results from our in vitro models confirmed that the ESR1 mutations conferred ligand-independent growth advantage and inability of fulvestrant to completely degrade the mutant forms of ERα.. On the other hand, CDK4/6 inhibitors inhibited the cell cycle progression and growth of cells with ESR1 mutations. Further in vivo studies using patient-derived xenograft tumors bearing an ESR1 mutation provided confirmation of the in vitro studies by demonstr (open full item for complete abstract)

Committee: Rashmi Hegde Ph.D. (Committee Chair); Samantha Brugmann Ph.D. (Committee Member); Kaushik Roychoudhury Ph.D. (Committee Member) Subjects: Surgery