EAPB0503, an Imidazoquinoxaline Derivative Modulates SENP3/ARF Mediated SUMOylation, and Induces NPM1c Degradation in NPM1 Mutant AML

Abstract

Nucleophosmin-1 (NPM1) is a pleiotropic protein involved in numerous cellular processes. NPM1 shuttles between the nucleus and the cytoplasm, but exhibits a predominant nucleolar localization, where its fate and functions are exquisitely controlled by dynamic post-translational modifications (PTM). Sentrin/SUMO Specific Peptidase 3 (SENP3) and ARF are two nucleolar proteins involved in NPM1 PTMs. SENP3 antagonizes ARF-mediated NPM1 SUMOylation, to promote ribosomal biogenesis. In Acute Myeloid Leukemia (AML), NPM1 is frequently mutated, and exhibits an aberrant cytoplasmic localization (NPM1c). NPM1c mutations define a separate AML entity with good prognosis in some AML patients, rendering NPM1c as a potential therapeutic target. SENP3-mediated NPM1 de-SUMOylation induces resistance to therapy in NPM1c AML. Here, we demonstrate that the imidazoquinoxaline EAPB0503 prolongs the survival and results in selective reduction in the leukemia burden of NPM1c AML xenograft mice. Indeed, EAPB0503 selectively downregulates HDM2 expression and activates the p53 pathway in NPM1c expressing cells, resulting in apoptosis. Importantly, we unraveled that NPM1c expressing cells exhibit low basal levels of SUMOylation paralleled with high SENP3 and low ARF basal levels. EAPB0503 reverted these molecular players by inducing NPM1c SUMOylation and ubiquitylation, leading to its proteasomal degradation. EAPB0503-induced NPM1c SUMOylation is concurrent with SENP3 downregulation and ARF upregulation in NPM1c expressing cells. Collectively, these results provide a strong rationale for testing therapies modulating NPM1c post-translational modifications in the management of NPM1c AML.

Current status and future perspectives in targeted therapy of NPM1-mutated AML

“…Treatment of the NPM1-mutated AML cell lines OCI-AML3 with deguelin, a rotenoid isolated from several plant species [46,47], and IMS-M2 with (-)-epigallocatechin-3-gallate (ECGT) [48], a major catechin found in green tea, were effective in reducing the NPM1 mutant but not the wild-type protein and in inducing apoptosis. Moreover, the imidazoquinoxaline derivative EAPB0503 induced a selective proteasome-mediated degradation of NPM1 mutant protein through EAPB0503-mediated SUMOylation and ubiquitylation [49]. This event was followed by restoration of NPM1 wild-type protein in the nucleolus [50], apoptosis (through selective downregulation of HDM2 and activation of p53 [49]) and reduction of leukemia burden in NPM1-mutated AML xenografts [49,50].…”

“…Moreover, the imidazoquinoxaline derivative EAPB0503 induced a selective proteasome-mediated degradation of NPM1 mutant protein through EAPB0503-mediated SUMOylation and ubiquitylation [49]. This event was followed by restoration of NPM1 wild-type protein in the nucleolus [50], apoptosis (through selective downregulation of HDM2 and activation of p53 [49]) and reduction of leukemia burden in NPM1-mutated AML xenografts [49,50]. Moreover, introducing NPM1-mutation into cells normally bearing wild-type NPM1 sensitized them to EAPB0503, leading to their growth arrest [50].…”

Identification of Potential Antitubulin Agents with Anticancer Assets from a Series of Imidazo[1,2-a]quinoxaline Derivatives: In Silico and In Vitro Approaches

“…Most synthesized imidazoquinoxaline-based anticancer compounds have shown an anticancer activity towards diverse cancer cell lines. However, the in vitro activity of these compounds has been reported to be suboptimal [ 8 , 9 , 10 , 11 ]. Thus, despite the great anticancer potential, the clinical implementation of these compounds is still lacking due to safety concerns and expected outcomes in clinical studies.…”

Imidazoquinoxaline as a Privileged Fused Pharmacophore in Anticancer Drug Development: A Review of Synthetic Strategies and Medicinal Aspects

“…[20] This further led to the development of EAPB203 and EAPB503 compounds, which are under clinical studies for further development. [21] Commercially, imidazoquinoxaline derivatives have profound applicability as dyes and luminescent materials. [22] In the last few years, several studies have been reported describing various synthetic strategies for the preparation of imidazoquinoxaline derivatives [23], such as π-conjugation of perylenes with external aromatic compounds, [24] solid phase and resin-based synthesis via a modified strategy for Pictet À Spengler reaction, [13,25] Van Leusen deprotectioncyclization, [26] using the microwave, [27] and cycloaddition of ethyl isocyanoacetate to 3-Chloro-2-(methylthio)/2-(methylsulfonyl) quinoxalines.…”

“…Imiquimod, marketed under the name Aldara®, is one of the first members of the imiqualines family that got approval for treatment of various types of cancer by the US FDA in 1997 [20] . This further led to the development of EAPB203 and EAPB503 compounds, which are under clinical studies for further development [21] . Commercially, imidazoquinoxaline derivatives have profound applicability as dyes and luminescent materials [22] .…”