A Druggable Tumor Suppressor and Leukemic Stem Cell Marker.

Acute myeloid leukemia (AML) often enters remission after chemotherapy but frequently relapses due to chemotherapy-resistant leukemic stem cells (LSCs). Relapsed AML remains largely unresponsive to current therapies and carries a poor prognosis. We developed a large-language model (LLM) agent that incorporates multi-modal data to nominate druggable therapeutic targets for AML. We identified that higher expression of AGTR2 (encoding AT2R) is associated with better chemotherapy response and longer survival. In functional studies of 68 primary human AML samples, we found that LSCs consistently lacked AT2R expression. Across both CD34-expressing and -non-expressing AML samples, AT2R expression positively correlated with CD34 and CD117 expression. In patient-derived xenograft (PDX) models using 21 primary AML samples, AT2R⁻ cells initiated leukemia, whereas AT2R⁺ cells failed to do so. AT2R⁻ cells gave rise to both AT2R⁺ and AT2R⁻ progeny, suggesting hierarchical differentiation. Following chemotherapy in AML PDX mice, bone marrow analysis showed a marked enrichment of AT2R⁻ cells and depletion of AT2R⁺ cells, indicating that AT2R⁻ cells drive minimal residual disease and relapse. These results support the role of AT2R absence as a marker of LSCs. We observed reduced AT2R expression in AML cells compared to healthy peripheral blood and bone marrow mononuclear cells, suggesting a tumor suppressor role. Whole-genome sequencing of AML patients revealed no functional mutations in AGTR2. However, 3D chromatin and epigenetic analyses uncovered frequent chromatin rearrangements involving AGTR2 promoter-silencer interactions, indicating epigenetic silencing as a likely mechanism for AT2R downregulation in AML. To validate the tumor suppressor role of AT2R, we developed murine AML models driven by MLL-AF9 or AML1-ETO9a fusions with either Agtr2 knockdown or enforced expression. Agtr2 knockdown accelerated leukemogenesis, while enforced Agtr2 expression delayed AML progression. In these models, enforced Agtr2 expression reduced LSC frequency, impaired cell cycle progression, and decreased AML stemness, as confirmed by limiting dilution assays and analysis of LSC-enriched populations. Mechanistically, enforced Agtr2 expression suppressed fatty acid metabolism - a key driver of AML stemness and growth - and inhibited downstream signaling pathways, including GSK3, PI3K/AKT, and Wnt/β-catenin. This led to reduced SREBF1 activity, confirmed by protein level changes and CUT&Tag assays. We tested buloxibutid (C21), a small-molecule AT2R agonist currently in phase II trials for idiopathic pulmonary fibrosis, in AML PDX models derived from 20 de novo and 6 relapsed AML samples. C21 significantly inhibited AML progression and enhanced the efficacy of chemotherapy, particularly in relapsed AML models.