Polyamines Are Required for AML LSC Function through Their Role in Regulating eIF5A Dependent Protein Synthesis

Abstract Outcomes for patients with acute myeloid leukemia (AML) remain poor due to the inability of current therapies to fully eradicate disease initiating leukemia stem cells (LSCs) (Shlush et al., 2017). Many studies have demonstrated that LSCs have unique metabolic properties compared to AML blasts (Jones et al., 2021). However, the metabolite profiles of human LSCs and hematopoietic stem and progenitor cells (HSPCs) have not yet been directly compared. To examine metabolite levels in enriched LSCs and HSPCs we used mass spectrometry-based metabolomics analysis on enriched LSCs from 18 AML patients and HSPCs from 9 normal bone marrow (BM) specimens. Pathway analysis showed that arginine metabolism and biosynthesis were the most significantly enriched pathways in LSCs compared to HSPCs. Clinical studies have shown limited efficacy of targeting arginine levels using arginine degrading enzymes; therefore, we sought to target pathways downstream of arginine. Stable isotope labeled tracing analysis showed arginine was metabolized through the urea cycle into polyamines in human LSCs. Polyamines are cationic compounds which have been previously shown to be important for the growth of various cancers but their role in AML LSCs has yet to be determined. To investigate if polyamines are essential for LSC survival and function, we treated LSCs and HSPCs with N1,N11-diethylnorspermine (DENSpm), a polyamine analog causing polyamine depletion through increased cellular export. DENSpm treatment decreased the viability of LSCs and AML blasts in 10 out of 12 of patients tested but had no impact on HSPC viability. Further, treatment with DENSpm resulted in decreased engraftment potential of the 4 AML specimens examined in immune deficient mice but did not alter the engraftment of normal HSPCs, suggesting that targeting polyamines represents a promising approach to kill LSCs while sparing HSPCs. We then investigated the mechanisms regulated by polyamines in LSCs. Using RNA-sequencing analysis on enriched LSCs from 5 AML patients and HSPCs from 3 normal BM specimens we observed decreased expression of genes involved in protein synthesis in DENSpm-treated LSCs but not normal HSPCs. Protein synthesis and its regulation are critical for AML survival (Chen et al., 2019; Messling et al., 2022) but the role of polyamines in protein translation in LSCs has not been explored. Polyamines stimulate translation notably by serving as precursors for the hypusination of eukaryotic translation initiation factor 5A (eIF5A) (Park et al., 2010). Accordingly, DENSpm led to reduced protein synthesis level in MOLM13 AML cell line and primary AML samples. Strikingly, protein synthesis and viability were rescued upon co-treatment with spermidine, suggesting that DENSpm induces AML cells death at least in part through decreased eIF5A-mediated protein translation. Altogether, our data demonstrates that depletion of polyamines decreased LSC function while sparing normal HSPCs. Mechanistically, our data suggest that LSC targeting is accomplished through polyamine regulated protein synthesis. Citation Format: Vincent Rondeau, Cristiana O’Brien, Jacob M Berman, Duhan Yendi, Tianyi Ling, Aleksandra Bourdine, Aarushi Gupta, Jonathan St-Germain, Rachel Culp-Hill, Julie A Reisz, Soheil Jahangiri-Tazehkand, Anastasia Tikhonova, Andrea Arruda, Mark D Minden, Angelo D’Alessandro, Brian Raught, Courtney L Jones. Polyamines are required for AML LSC function through their role in regulating eIF5A dependent protein synthesis [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr A54.