IL-1 Via IRAK1/4 Sustains Acute Myeloid Leukemia Stem Cells Following Treatment and Relapse

Current treatment options for relapsed acute myeloid leukemia (AML) are limited and ineffective for the majority of patients. In AML, primitive leukemia stem cells (LSCs) and pre-leukemic populations are able to maintain the disease and drive relapse. Thus, therapies targeting LSC populations may increase the overall survival of AML patients. In this study, we aim to identify the drivers favoring LSC expansion following treatment and relapse and develop potential therapies for AML. The transcriptome analyses of 12 pairs of functionally defined LSC fractions at diagnosis and relapse revealed significant changes of IL-1 signaling in AML patients. We demonstrated that the protein expression levels of interleukin-1 receptor type I (IL1R1) and its complex member interleukin-1 receptor accessory protein (IL1RAP) were both up-regulated in human leukemia stem and progenitor cells (LSPCs) at diagnosis or in relapse compared to normal hematopoietic stem and progenitor cells (HSPCs). Knockdown of IL1R1 and IL1RAP suppressed the clonogenicity and engraftment growth of primary human AML cells but showed low impacts on HSPCs in the normal bone marrow. Additionally, knockout of IL1R1 in leukemia MLL-AF9 mice significantly reduced the LSC frequency and prolonged the overall survival rate. To target IL-1/TLR signaling in LSCs, we performed iterative structure-activity relationship (SAR) guided medicinal chemistry, in silico modeling and leukemia cell line reporter assays to screen and identify a novel interleukin-1 receptor-associated kinase 1/4 (IRAK1/4) inhibitor (termed UR241-2). UR241-2 robustly inhibits IL-1/TLR signaling in AML cells including the activation of NF-κB following IL-1 stimulation. UR241-2 repressed LSPC function as assessed by colony-forming unit assays in primary human AML cells at diagnosis and in relapse while minimally impacting normal HSPC function. Taken together, our findings demonstrate the important role of IL-1/TLR signaling in supporting AML LSC expansion following treatment and relapse and suggest that targeting IL-1/TLR signaling using the novel IRAK1/4 inhibitor, UR241-2, can target LSC function to improve patient outcomes in AML.