Effect of the Immunomodulatory Drug EAP0503 on Mutant Nucleophosmin-1 Function in Acute Myeloid Leukemia

Abstract

Nucleophosmin-1 mutation (NPM1c) represents one of the most frequent mutations in Acute Myeloid Leukemia (AML). In NPM1c AML, NPM-1 is aberrantly exported to the cytoplasm, contributing to leukemogenesis. Ribosomal biogenesis depends on NPM1 binding with the SUMO-specific protease SENP3 or the p14Arf protein. While SENP3 catalyses desumoylation of NPM1-SUMO2 leading to 28S rRNA maturation; NPM1-p14Arf binding counteracts this activity. p14Arf binds and activates p53, through antagonizing its ubiquitin ligase MDM2. In this study, we explored the effect of NPM1c on the complex interaction with SENP3, p53, MDM2 and investigated the molecular basis of the immunomodulatory drug EAPB0503-induced NPM1c degradation on this interaction. We used two AML cell lines, OCI-AML2 and OCI-AML3 expressing NPM1 and NPM1c respectively. In vitro, the effect of EAPB0503 on cell growth, cell cycle, expression levels and localization of NPM1c, SENP3, p53, P-p53, MDM2 and p21 were assessed. EAPB0503 inhibited OCI-AML3 proliferation in a time-dependent manner and led to NPM1c degradation through p53 pathway activation. This was accompanied by restored NPM1 nucleolar localization in NPM1c AML cells. Importantly, NPM1c AML cells exhibited low basal levels of p53, and high basal levels of SENP3 and MDM2. EAPB0503 selectively degraded SENP3 in NPM1c AML cells, resulting in SUMOylation of NPM1c. In vivo, immunocompromised mice were injected intravenously with either cell lines. EAPB0503 was administered intraperitoneally, every other day, for 3 weeks. EAPB0503 selectively prolonged survival of OCI-AML3 xenograft mice, preserved the normal liver architecture, and reduced the number of bone marrow blasts along with NPM1c degradation, and p14ARF upregulation. This study provides a rationale for the therapeutic use of EAPB0503 in NPM1c AML.