Abstract 272: Novel role for eIF4E in homing of acute myeloid leukemia cells
Authors: Martinez Leandro M. , Lopes Eloisi Caldas , Sugita Mayumi , Gasiorek Jadwiga , Alilovic Kata , Borden Katherine L. , Guzman Monica L. 
Published: March 2024

Abstract
Acute myeloid leukemia (AML) remains with dismal outcomes, mostly attributed to the inability of therapies to eliminate leukemia stem cells (LSCs) leading to relapse. LSCs home to the bone marrow (BM) niche where they maintain their quiescence state once in contact with mesenchymal stromal cells (MSCs). Therefore, understanding what controls AML-niche interactions could lead to therapeutic approaches that can prevent relapse.
First, we implemented a novel 3D in vitro system to mimic human AML-niche interactions. This 3D structure consists of a spheroid formed with BM-MSCs (HS5 cell line), recreating a hypoxic microenvironment. When AML cells (MM6 cell line) are added to the spheroid in a 1:1 proportion, AML cells migrate to the spheroid. After 24 hours, 0.18% of the AML cells home/colonize the spheroid (n=8). Next, we assessed the cell cycle status of AML cells in co-culture with the spheroid and compare to those in liquid culture or placed on a MSC monolayer (2D). We found that cells upon contact with MSCs increased their quiescence, 18.63% G0 in 2D and significantly higher in 3D conditions (25.03%; p=0.0048). It is also important to point out that colonizing cells have a lower proliferate capacity than non-colonizing cells after 7 days of co-culture (p=0.0286). This quiescence feature suggests a stem-like behavior of cells homing to the spheroid.
Eukaryotic translation initiation factor 4E (eIF4E) has been found altered in AML. While the capacity of eIF4E to increase cell migration and growth has been shown in solid cancers, the mechanism of eIF4E to accelerate AML progression remains unknown. Thus, we hypothesized that eIF4E may play a role in homing of AML cells to the niche. To this end, we used CRISPR to deplete eIF4E in MM6 cells and found that CRISPR 4E cells have significantly decreased homing capacity to the spheroid compared with control cells (p=0.0065). Importantly, we found a lower percentage of CRISPR 4E cells underwent quiescence after co-culture with MSCs (2D or 3D) (p&lt;0.0001). We corroborated observations using xenograft mice. After 20 hours of intravenous injection, we observed a higher percentage of AML cells in the blood of the mice injected with CRISPR 4E cells compared with control cells (p=0.0286), suggesting that CRISPR 4E cells are not able to effectively exit from peripheral blood to home to their niche.
Altogether, we stablished a novel in vitro 3D model that mimics stem cell features of the AML-BM niche. We demonstrated that the depletion of eIF4E in AML cells decreases their homing and prevents them from acquiring niche-induced quiescence.
Citation Format: Leandro M. Martinez, Eloisi Caldas Lopes, Mayumi Sugita, Jadwiga Gasiorek, Kata Alilovic, Katherine L. Borden, Monica L. Guzman. Novel role for eIF4E in homing of acute myeloid leukemia cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 272.