Specific Targeting and Novel Molecular Players in Leukemogenesis Associated with Mutant Nucleophosmin

Acute myeloid leukemia (AML) is the most common acute leukemia in adults. In AML, NPM (nucleophosmin) is the most frequently mutated gene. NPM is a nucleolar shuttling protein that interacts with several proteins, and mediates their correct subcellular localization and stability. Mutations of NPM lead to aberrantly localized cytoplasmic NPM (NPMc+), which has been implicated in driving leukemogenesis. This thesis aims at studying the role of NPM and its interaction network to elucidate how dysregulation and delocalization of NPM potentially affects drug sensitivity and resistance in AML. Pharmacological inhibitors of CDK4/6 (palbociclib) and FOXO1 (AS-1842856) were utilized to study the inhibitor sensitivity of OCI-AML2 (wt NPM) and OCI-AML3 (NPMc+) cells, and effects on cell viability were assessed with MTS assay. NPM interactions were studied with anti-NPM immunoprecipitation, and three known interactors (PELP1, SENP3 and p14ARF) and one putative novel interactor candidate were tested for protein-protein interactions. The effects of inhibitors on target protein expressions and verification of successful immunoprecipitation were assessed with immunoblotting. Inhibition of CDK4/6 had anti-proliferative effects in OCI-AML2 and OCI-AML3, which likely arises from the suppression of retinoblastoma protein phosphorylation. Depending on cell line and duration of treatment, inhibition of FOXO1 exerted either pro-proliferative or anti-proliferative effects, indicating that FOXO activity may vary between these AML cell lines. NPM was verified to interact with ribosome biogenesis-associated proteins SENP3 and PELP1 in leukemia cells. NPM also displayed a potential novel interaction with the candidate protein, which may implicate that NPM has a role in regulation of its stability