Unleashing intrinsic inflammation in AML using therapeutic cytokines overcomes pro-survival pathways and induces deep and durable remission In Vivo.

Abstract Acute myeloid leukemia (AML) remains a clinical challenge due to high relapse rates, primarily driven by therapy-resistant leukemic stem and progenitor cells (LSCs). We proposed that intrinsic inflammatory signaling events serve as a survival mechanism in leukemic cells, but that the balance between beneficial and deleterious inflammatory signaling is finely regulated and context-dependent. Indeed, we have previously shown that TNF receptor 1 (TNFR1)-dependent signaling readily kills AML in vivo by activating Receptor-interacting protein kinase 3 (RIPK3) (PMID: 27411587). Hence, we speculated that disruption of critical pro-survival signaling nodes downstream of TNFR1 can be leveraged therapeutically. In this study, we describe a novel cytokine-based therapeutic strategy that selectively kills LSCs while simultaneously preserving and even supporting normal hematopoiesis. Using syngeneic murine FLT3-ITD-driven AML models, we found that genetic deletion of the specific TNF superfamily cytokine lymphotoxin alpha (LTA) disrupts cell death pathways and accelerates leukemogenesis, underscoring its role as an intrinsic tumor suppressor. Importantly, therapeutic administration of lymphotoxin alpha as recombinant cytokine reactivated a suppressed RIPK3-dependent signaling cascade, leading to cell death of leukemic progenitor cells and, in parallel, to myeloid differentiation of the leukemic clone. In both syngeneic and patient-derived xenograft (PDX) models representing common oncogenic driver mutations, cytokine monotherapy induced deep and sustained remissions (>300 days), highlighting its efficacy as single agent. Mechanistically, the anti-leukemic activity is mediated through depletion of the pro-survival adaptor molecule TNF Receptor-Associated Factor 2 (TRAF2) in the TNFR1 complex I. Notably, this approach spares normal hematopoietic cells due to the presence of a robust pool of TRAF2. Resembling the physiological process of cytokine-mediated emergency granulopoiesis, we even observed propagation of hematopoietic progenitor populations thereby offering a distinct advantage over conventional cytotoxic treatments, which often suppress bone marrow function. These findings reveal a potentially actionable immune mechanism that could shift AML treatment paradigm by uncoupling therapeutic efficacy from toxicity on the healthy hematopoeisis, and provide a rationale for further clinical development of cytokine-based therapies in AML.