MS, University of Cincinnati, 2024, Medicine: Cancer and Cell Biology

Acute myeloid leukemia (AML) is a rare hematological malignancy characterized by genetic and epigenetic aberrations in hematopoietic progenitor/stem cells (HPSCs). Molecular profiling studies of AML patients have suggested a sequential acquisition of co-occurring mutations during leukemogenesis, with mutations in epigenetic regulatory genes like TET2 and DNMT3A often serving as the initiating events due to their high variant allele frequencies (VAF). Moreover, these initiating mutations exhibit a key role in clonal hematopoiesis (CH), a state marked by the expansion of dominant mutant HPSC clones without evident disease. Concurrent mutations, notably in genes such as NPM1, NRAS, and FLT3, are known to co-occur with epigenetic modifier mutations and are believed to manifest within a pre-existing mutant clone. While targeted therapies have been established for specific AML mutations like FLT3 and IDH1/2, treating patients lacking these mutations or those who develop resistance remains a critical challenge. Recent strides in single-cell sequencing have revolutionized our comprehension of AML pathogenesis by unveiling the clonal architecture and mutation order, which is not possible through bulk sequencing approaches. Leveraging technologies such as single-cell targeted DNA sequencing, we and others have dissected genetic variations at the single-cell level, unraveling how specific combinations of mutations, such as TET2/NPM1, can synergistically propel leukemogenesis, resulting in the amplification of double mutant clones compared to single mutant clones. Furthermore, single-cell multi-omics investigations have delineated that the co-mutational context exerts a profound impact on the differentiation and immunophenotype of transformed cells. Investigating distinct genotypic states in AML aims to furnish invaluable insights into the intricate web of co-mutational synergy and the influence of mutation chronology on leukemia progression, ultimately directing the developmen (open full item for complete abstract)

Committee: Linde Miles Ph.D. (Committee Chair); Andrew Volk Ph.D. (Committee Member); Erin Hertlein Ph.D. (Committee Member) Subjects: Oncology

Doctor of Philosophy, The Ohio State University, 2017, Biomedical Sciences

Melanoma accounts for the vast majority of skin cancer-associated deaths and the incidence is increasing faster than any other cancer in the US. It is estimated that 87,000 new cases of melanoma will be diagnosed in the US in 2017. NRAS is the second most commonly mutated oncogene in melanoma, altered in 15-20% of cases, and efforts to therapeutically target NRAS and other RAS oncogenes have proven difficult. Recently, our group discovered that the NRAS gene transcript is differentially spliced to give rise to 5 distinct NRAS isoforms of varying size, expression patterns and downstream effects. Thus, we characterized the expression patterns and phenotypic functions of these isoforms in melanoma. All five NRAS isoform transcripts were expressed in melanoma tumor tissue, with canonical NRAS (isoform 1) consistently expressed to the highest degree. NRAS isoform 1 mRNA expression was also significantly increased in metastases compared to primary melanoma lesions. Isoform 5 mRNA expression was found to be significantly correlated with survival, as high levels of isoform 5 in metastases were associated with enhanced survival in these patients with stage IV disease. Forced over-expression of each the isoforms led to enhanced proliferation, but invasiveness was only increased with over-expression of isoforms 1 or 2. Over-expression of isoform 4 led to significantly decreased ability to engage in anchorage-independent cell growth. Downstream signaling analysis indicated that the isoforms varied in their ability to mediate signaling through the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase pathways. In vivo growth of A375 cells over-expressing each of the isoforms showed that cells over-expressing isoform 5 had significantly decreased tumor growth. Finally, A375 cells over-expressing isoforms 2 or 5 showed marked resistance to vemurafenib treatment in vitro. The results from this study indicate that the five different isoforms of NRAS (open full item for complete abstract)

Committee: William Carson, III MD (Advisor); Robert Baiocchi MD, PhD (Committee Member); Balveen Kaur PhD (Committee Member); Susheela Tridandapani PhD (Committee Member) Subjects: Biomedical Research