Leukemia

BackgroundPatients with active acute myelogenous leukemia (AML) are at risk for leukemic infiltration (LI) into the lung and acute tumor lysis pneumopathy (ATLP) following chemotherapy. Fulminant presentations of these leukemic lung diseases are well-described, but indolent forms have not yet been studied. Therefore, we sought to elucidate the clinical features of mild-to-moderate LI and ATLP. MethodsA retrospective cohort analysis was performed on 51 hospitalized patients with AML, circulating blast count [≥]3%, non-critical illness, and receipt of bronchoscopy between 2015-2019. Diagnoses of LI and ATLP were made via retrospective chart review by a multidisciplinary team of physicians. Results19 cases of leukemic lung disease were identified: 14 with LI and 5 with ATLP. The clinical presentations closely resembled pneumonia, with the majority demonstrating respiratory symptoms (63%), hypoxemia (63%), fever (84%), and pulmonary opacities (100%). All patients were presumptively diagnosed with infection, leading to an average of 18 days of broad-spectrum antibiotic therapy and multiple instances of delayed chemotherapy in treatment candidates. Although most patients were near the end-of-life (90% died within 1 year), transitions to comfort care were infrequent (25%) and hospitalizations were protracted (median 25 days). ConclusionsLI and ATLP are common yet under-recognized pulmonary complications in patients with active AML. When presenting indolently, these conditions are difficult to distinguish from lung infection, leading to missed diagnosis, inappropriate antibiosis, chemotherapy deferrals, and prolonged hospitalizations. Greater awareness and consensus definitions of LI and ATLP are therefore needed to improve care of this population.

The 5th Edition of the World Health Organization Classification of Haematolymphoid Neoplasms (WHO5th) and the 2022 International Consensus Classification (ICC) both recognize myelodysplasia-related acute myeloid leukemia (AML-MR) as a diagnostic entity increasingly defined by integrated genomic data. Although largely concordant, the two classifications differ in various ways that should be resolved to achieve future harmonization. To address the areas of uncertainty, we retrospectively analyzed 615 newly diagnosed AML cases from adult patients treated at two large cancer centers. We demonstrate that AML-MR, whether defined by gene mutations (MR-GM) or cytogenetic abnormalities (MR-CGA), constitutes a prognostically distinct group with inferior outcome compared to most AML subtypes, second only to TP53-mutated or EVI1-rearranged AML. Isolated RUNX1 mutations were not associated with antecedent myeloid neoplasia. Neither the number of mutated MR genes nor their variant allele frequency independently impacted outcomes. Trisomy 8 and del(20q) did not confer inferior outcomes and may warrant exclusion from MR-CGA. Complex karyotype without TP53 mutations did not worsen outcomes within AML-MR and may be considered equivalent to other MR-CGA. The adverse prognosis of AML-MR appeared to be at least partly driven by ASXL1 and/or EZH2 mutations. These findings provide evidence toward a unified schema across the WHO5th and ICC.

NPM1 encodes for a nucleolar multifunctional protein and is the most frequently mutated gene in adult acute myeloid leukemia (AML). NPM1 mutations cause the aberrant accumulation of mutant NPM1 (NPM1c) in the cytoplasm of leukemic cells, that is mediated by the nuclear exporter Exportin-1 (XPO1). Recent work has demonstrated that the interaction between NPM1c and XPO1 promotes high homeobox (HOX) genes expression, which is critical for maintaining the leukemic state of NPM1-mutated cells. However, the XPO1 inhibitor Selinexor administered once or twice/week in early-phase clinical trials did not translate into clinical benefit for NPM1-mutated AML patients. Here, we demonstrate that this dosing strategy results in only temporary disruption of the XPO1-NPM1c interaction and transient HOX genes downregulation, limiting the efficacy of Selinexor in the context of NPM1-mutated AML. Since second-generation XPO1 inhibitors can be administered more frequently, we compared intermittent (twice/week) versus prolonged (5 days/week) XPO1 inhibition in NPM1-mutated AML models. Integrating in vitro and in vivo data, we show that only prolonged XPO1 inhibition results in stable HOX downregulation, cell differentiation and remarkable anti-leukemic activity. This study lays the groundwork for the accurate design of clinical trials with second-generation XPO1 inhibitors in NPM1-mutated AML.

In both neonates and adults, the presence of malignancy-associated mutations in peripheral blood (PB) correlates with an elevated risk of future neoplastic transformation, with certain mutations, such as KMT2A rearrangements, exhibiting near-complete penetrance. If feasible, pre-malignant screening could enable early intervention and even disease prevention. However, nucleic acid sequencing- and hybridization-based mutation detection have limited cost-efficiency, constraining their use in screening. Here, we introduce a computer vision platform that can identify mutant cells in fresh PB samples that carry KMT2A-MLLT3 (a frequent mutation in pediatric and adult leukemias and detectable in newborn blood samples) or JAK2-V617F (a frequent mutation in myeloproliferative neoplasms and clonal hematopoiesis). This is achieved by high-throughput single-cell imaging and mutation detection by machine learning (ML)-powered morphology recognition. The ML models were developed by cross-species learning of conserved features between mutant cells from mouse genetic models and from human samples, enabling a cost-effective approach for detecting mutations in live blood cells. This platform holds promise for pre-malignant screening in asymptomatic neonates and adults with KMT2A-MLLT3 or JAK2-V617F mutation and is potentially generalizable to the detection other malignancy-associate mutations. Our platform provides a novel single-cell morphological data modality that complements existing single-cell genomics.

Acute myeloid leukemia (AML) is a clinically aggressive and molecularly heterogeneous malignancy. Current prognostic standards, such as the European LeukemiaNet (ELN) classification, do not fully capture its regulatory complexity. We developed a two-step, PCA-based survival workflow that independently and jointly models gene and miRNA expression to identify biomarkers for patient risk stratification, followed by support vector machine validation across multiple AML cohorts. This strategy enabled rigorous cross-validation while capturing genome-wide regulatory variation. This approach yielded a 19-gene panel--including known oncogenes (e.g., HMGA2, TAL1) and novel candidates (e.g., MLEC, APOE)--that showed robust prognostic performance with validation AUCs>0.879. Parallel analyses identified a 16-miRNA panel enriched for tumor suppressors (e.g., miR-7b-3p, miR-26a-5p) and novel markers (e.g., miR-3613-5p, miR-942-5p), achieving validation AUCs up to 0.916. Integrating experimentally supported miRNA:target interactions revealed 10 coherent regulatory pairs, most showing inverse correlations consistent with miRNA-mediated regulation. Incorporating these regulatory relationships improved prognostic performance compared with single-omic models. Finally, we derived a Cox regression-based molecular risk score that robustly stratified patients and outperformed ELN-2022 risk classification across cohorts. Overall, this framework yields biologically grounded, compact, and reproducible biomarkers with strong prognostic power and provides a generalizable strategy for integrative regulatory modeling in AML.

Measurable residual disease (MRD), defined as the population of cancer cells which persists following therapy, serves as the critical reservoir for disease relapse in acute myeloid leukemia (AML) and other malignancies. Understanding the biology enabling MRD clones to resist therapy is necessary to guide the development of more effective curative treatments. Discriminating between residual leukemic clones, preleukemic clones and normal precursors remains a challenge with current MRD tools. Herein, we developed a single cell (sc) MRD assay by combining flow cytometric enrichment of the targeted precursor/blast population with integrated scDNA sequencing and immunophenotyping. Our scMRD assay shows high sensitivity of approximately 0.01%, deconvolutes clonal architecture and provides clone-specific immunophenotypic data. In summary, our scMRD assay enhances MRD detection and simultaneously illuminates the clonal architecture of clonal hematopoiesis/pre-leukemic and leukemic cells surviving AML therapy. Statement of significanceScMRD assay integrates mutation and immunophenotype at single cell resolution and therefore distinguishes clonal hematopoiesis/preleukemic vs. leukemic clones. This study serves as a framework for identifying high-risk MRD clones and improving our understanding of both the molecular drivers and vulnerabilities of therapy resistant AML clones.

Mixed phenotype (MP) in acute leukemias poses unique classification and management dilemmas and can be seen in entities other than de novo mixed phenotype acute leukemia (MPAL). Although WHO classification empirically recommends excluding AML with myelodysplasia related changes (AML-MRC) and therapy related AML (t-AML) with mixed phenotype (referred to as "AML-MP") from MPAL, there is lack of studies investigating the clinical, genetic, and biologic features of AML-MP. We report the first cohort of AML-MP integrating their clinical, immunophenotypic, genomic and transcriptomic features with comparison to MPAL and AML without MP. Patients with AML-MP share similar clinical and genetic features to its AML counterpart but differs from MPAL. AML-MP harbors more frequent RUNX1 mutations than AML without MP and MPAL. RUNX1 mutations or complex karyotypes did not impact the survival of MPAL patients. Unsupervised hierarchal clustering based on immunophenotype identified biologically distinct clusters with phenotype/genotype correlation and outcome differences. Furthermore, transcriptomic analysis showed an enrichment for stemness signature in AML-MP and AML without MP as compared to MPAL. Lastly, MPAL but not AML-MP often switched to lymphoid only immunophenotype after treatment. Expression of transcription factors critical for lymphoid differentiation were upregulated only in MPAL, but not in AML-MP. Our study for the first time demonstrates that AML- MP clinically and biologically resembles its AML counterpart without MP and differs from MPAL, supporting the recommendation to exclude these patients from the diagnosis of MPAL. Future studies are needed to elucidate the molecular mechanism of mixed phenotype in AML. Key pointsAML-MP clinically and biologically differs from MPAL but resembles AML. AML-MP shows RUNX1 mutations, stemness and limited lineage plasticity.

Extramedullary acute myeloid leukemia (eAML) represents a clinically challenging manifestation of acute myeloid leukemia (AML), but its molecular drivers remain poorly defined. We performed targeted sequencing in 85 eAML biopsies, representing one of the largest molecular analyses of eAML to date. We detected mutations in RAS or RAS-modifying genes (RASMUT; NRAS, KRAS, PTPN11, CBL, and NF1) in 41% of cases, representing a significant enrichment compared to bone marrow (BM) samples of more than 1300 AML patients not selected for eAML. Analysis of paired eAML and BM specimens revealed expansion and/or de-novo appearance of RASMUT clones at the extramedullary site. Functional studies using primary murine leukemia cells and CRISPR/Cas9-engineered isogenic human leukemia cell lines demonstrated that RASMUT increase the migration and invasion of leukemic cells compared to RAS-wildtype controls. Consistently, RASMUT cells showed increased infiltration into the chorioallantoic membrane of chicken embryos and demonstrated enhanced extramedullary growth after injection into immunocompromised mice. RNA sequencing revealed increased expression of junctional adhesion molecule-like (JAML) and activation of PI3K/AKT signaling in RASMUT cells. JAML silencing and pharmacologic AKT inhibition reversed the RASMUT-driven effects on leukemic cell migration, demonstrating a causal role of the JAML-PI3K/AKT axis in RASMUT-driven eAML formation. In conclusion, these findings delineate the molecular landscape of extramedullary AML and show that RASMUT are enriched within this AML subform. They further demonstrate that RASMUT actively contribute to leukemic tissue infiltration through activation of a RASMUT-JAML-PI3K/AKT axis, highlighting AKT signaling as a potential therapeutic vulnerability in RASMUT-associated eAML.

Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) have a propensity to transform to an accelerated or blast phase (MPN-AP/BP). The resulting disease has clinically similar manifestations to Acute Myeloid Leukemia (AML) but worse clinical outcomes. Here we present the first comprehensive description of the transcriptomic characteristics of MPN-AP/BP. Our analysis incorporates data from 261 patients of the BeatAML cohort and 56 MPN-AP/BP patients, 11 of whom had paired samples from before and after transformation. We establish that transformed MPN is a transcriptionally distinct entity from de novo AML and chronic phase MPNs. Genomic pathways traditionally associated with MPN pathogenesis, such as IL2/STAT5 signaling, IL6/JAK/STAT3 signaling, and NUP98/HOXA9 fusions, were enriched in chronic-phase MPNs but are absent in transformed disease, suggesting JAK2 directed therapy may be less effective in this disease phase. We also discovered that gene expression signatures associated with doxorubicin resistance are highly enriched in transformed MPNs, which may explain the lack of efficacy of standard AML therapies. In addition, we identify that lineage composition at the time of transformation may define distinct subsets of MPN-AP/BP patients, which may assist in the future development of novel treatment strategies. Key Points- Accelerated- and blast-phase transformed MPNs are a transcriptionally entities which are distinct from de novo AML. - Transformed MPNs may be characterized by their lineage characteristics, which can drive clinical behavior and account for their inferior overall survival - Gene expression signatures associated with doxorubicin resistance were highly enriched in transformed MPNs, which may explain the lack of effectiveness of anthracycline-based therapies

Acute myeloid leukemia (AML) is the most common acute leukemia in adults and is associated with poor outcomes due to frequent relapse after remission induction. While hematopoietic stem cell transplantation (HSCT) can improve survival, many individuals, especially older patients, are ineligible. Prior immunotherapies have not reliably induced effective anti-leukemic immunity and have been associated with severe and unpredictable toxicities. Thus, there is a need for safe and effective therapies that reduce relapse and increase overall survival (OS). We have developed a universally applicable, patient-specific, lentivirally engineered autologous AML cell vaccine, TriLeukeVax (TLV), designed to stimulate leukemia-specific cytolytic immune responses in AML patients in remission. To generate TLV, AML cells are engineered to express the highly synergistic combination of the co-stimulatory protein CD80 and the IL-15/IL-15-receptor alpha (IL-15R) heterodimer. Prior proof-of-concept (POC) studies demonstrated eradication of disease in >80% of leukemic mice with serial administration of TLV. In the current studies, TLV was generated from 59/60 cryopreserved, diagnostic bone marrow-derived patient AML samples. Ex vivo priming of post-remission patient T-cells by ex vivo co-culture with autologous TLV stimulated robust proliferative and cytotoxic responses. In secondary co-cultures, T-cells previously primed by initial co-culture with TLV, showed greater clonal expansion and leukemia-specific cytolytic activity towards de novo autologous AML blasts than did control, unprimed T-cells. The enhanced anti-leukemic activity of TLV-primed T-cells against de novo AML confirms the potential for vaccine administration to effectively target minimal residual disease (MRD) persisting after chemotherapy and reduce relapse. Key PointsO_LITriLeukeVax induces proliferation, activation, and effective anti-leukemic cytolytic responses in remission T-cells. C_LIO_LIPrimed T-cells show polyclonal expansion and transcription profiles associated with proliferation, memory, and cytotoxicity. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=177 SRC="FIGDIR/small/687000v2_ufig1.gif" ALT="Figure UFIG"> View larger version (38K): org.highwire.dtl.DTLVardef@5c1827org.highwire.dtl.DTLVardef@35b2e2org.highwire.dtl.DTLVardef@1732914org.highwire.dtl.DTLVardef@18df655_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOVisual Abstract.C_FLOATNO TriLeukeVax (TLV) workflow and mechanism of action. Diagnostic AML patient bone marrow aspirates are collected, purified in Ficoll and cryopreserved. Samples are thawed and lentivirally transduced to produce TLV. Vaccination of AML patients in remission with TLV will stimulate the activation and expansion of leukemia-specific T-cells, effector memory cells, and NK cells by combining the co-stimulatory effects of CD80 with immune stimulation by the IL-15/IL-15R heterodimer expressed by the transduced AML cells, thereby targeting MRD and potentially increasing relapse-free survival in AML patients. C_FIG

The KMT2A::MLLT3 fusion protein causes acute myeloid leukemia (AML) by activating the oncogenic transcription factor MECOM. However, MECOM expression occurs in only half of the KMT2A::MLLT3 cases. By integrating gene expression and enhancer activity data from patient cells, we identified neuronal homeobox transcription factor HMX3 as cell fate determining factor in MECOM-negative KMT2A::MLLT3 AML. HMX3 expression associated with younger age and KMT2A-rearranged leukemia in large AML cohorts (p<0.002). HMX3 was not expressed in other major genetic risk groups and healthy blood cells. Transcriptomic analyses revealed that HMX3 drives cancer-associated E2F, MYC and cell cycle gene programs. Ectopic HMX3 expression completely inhibited monocytic but not granulocytic colony formation of healthy CD34+ adult cells. Silencing of HMX3 in KMT2A::MLLT3 AML cell lines and patient cells resulted in cell cycle arrest, monocytic differentiation, and apoptosis. Thus, HMX3 is a leukemia-specific vulnerability that enhances proliferation and blocks differentiation of MECOM-negative KMT2A::MLLT3 leukemia.

The European LeukemiaNet (ELN) risk stratification of acute myeloid leukemia (AML) uses genetic and molecular markers to categorize patients. However, disease heterogeneity, particularly in the intermediate-risk group, complicates stratification. Ideker et al. developed the Network-Based Stratification (NBS) method, combining protein network analysis and mutation profiling via machine learning. We applied NBS to intermediate- risk AML patients to refine prognosis and identify distinct molecular subtypes compared to the 2022 ELN scheme. We selected 170 intermediate-risk AML patients based on the 2022 ELN classification from TCGA (n=58), BEAT AML (n=87), and FIMM (n=25) datasets. Using NBS, we analyzed 3,108 genes from WGS or WES data, mapping them onto a cancer-specific protein network for clustering based on network-propagated mutation profiles. We conducted 200 iterations of sub-sampling, considering patients with at least 3 mutated genes and using consensus clustering for robust stratification, assessing associations with clinical and transcriptomic features. NBS identified five distinct molecular subgroups characterized by unique mutation patterns: IDH1-dominant (Cluster 1), DNMT3A-dominant (Cluster 2), low-frequency multi-mutated (Cluster 3), FLT3/NPM1/DNMT3A co- mutated (Cluster 4), and FLT3-dominant (Cluster 5). Cluster 4 showed significantly worse overall survival (HR = 1.81; p = 0.05). In addition, ex vivo drug sensitivity and transcriptomic analyses revealed significant variation in therapeutic response and pathway activation across clusters. These findings underscore the power of machine learning-driven approaches like NBS to uncover hidden molecular structure within intermediate-risk AML groups, enabling more precise prognostication and potentially informing personalized therapeutic strategies. Key pointsO_LIML-based NBS stratification reveals distinct subgroups within intermediate-risk AML with unique molecular and clinical profiles. C_LIO_LIAML with NPM1/FLT3-ITD/DNMT3A mutations define a high-risk group with distinct drug sensitivities, including FLT3 inhibitors. C_LI

Despite important progress over the last decade, acute myeloid leukemia (AML) is still associated with poor clinical outcome. Novel potent therapies ideally effective against AML stem cells (LSC), a major driver of leukemia initiation and progression, are urgently needed. In particular, targeting common AML-associated antigens at the stem and progenitor cell level represents an attractive therapeutic strategy to achieve deep long-term remissions and is currently the subject of intensive research efforts. In this study, we identified the tetraspanin CD81, a cell surface antigen frequently expressed on AML cells including LSC, as a new determinant of relapse and poor prognosis. CD81 expression was higher in AML cells compared to normal bone marrow cells, and more markedly expressed at relapse. We further showed that modulation of CD81 expression using gain- and loss-of-function approaches affected leukemia aggressiveness, tumor burden, LSC-homing and - xenoengraftment as well as mouse survival. Finally, anti-hCD81 monoclonal antibody-treatment combined with standard chemotherapy in mice with pre-established AML not only reduced leukemia burden but also prolonged relapse-free and overall survival. Collectively, these results identified a new efficacious and safe pharmacological strategy for targeting LSC, opening up novel therapeutic avenues to improve AML outcome. Key pointsO_LICD81 expression in AML including LSC is a new determinant of aggressive disease and poor prognosis. C_LIO_LIAnti-hCD81 monoclonal antibody-treatment of AML xenografts reduced leukemia burden and improved survival rates. C_LI

Applying transcriptional profiling analysis to myeloblasts from 59 adult patients with acute myeloid leukemia (AML) treated at our institution, we found that expression of the three-amino acid loop extension (TALE) homeobox gene TG-Interacting Factor 1 (TGIF1) correlated with overall and relapse-free survival, which was then confirmed in two other cohorts of patients. Moreover, TGIF1 expression correlated with survival for all cytogenetic risk groups and was an independent prognostic factor in multivariate analysis. To elucidate the mechanism, we used Tgif1 knockout mice in which acute or chronic myeloid leukemia was induced through retroviral transfer of the MLL-AF9 or BCR-ABL fusion genes into bone marrow cells. Loss of Tgif1 accelerated disease progression, shortened survival, attenuated the response to chemotherapy, and doubled the frequency of leukemia-initiating cells. RNA-based sequencing analysis showed that genes associated with transforming growth factor-{beta} (TGF-{beta}) and retinoic acid signaling pathways were differentially affected in Tgif1-/- compared to Tgif1+/+ leukemia cells.

Mutations activating RAS/RAF/MEK/ERK signaling are associated with poor outcome in acute myeloid leukemia (AML), but therapeutic targeting of this pathway is challenging. Here, we employ a structure-based, dynamic RAS pathway model to successfully predict RAF inhibitor (RAFi) combinations which synergistically suppress ERK signaling in RAS-mutant AML. Our in silico models predicted therapeutic synergy of two iterations of conformation-specific RAF inhibitors: Type I[1/2] + Type II and Type I + Type II. Predictions were validated in vitro in AML cell lines and patient samples, with synergy verified by the Loewe Additivity model. Lifirafenib (Type II) + encorafenib (Type I[1/2]) was highly synergistic against both NRAS- and KRAS-mutant lines, while synergy of lifirafenib + SB590885 (Type I) was specific to NRAS-mutants. Immunoblotting confirmed that combination efficacy correlated strongly with decreased RAS pathway activation. Leveraging the pharmacokinetic predictions of our in silico model, both combinations were then assessed in a pre-clinical NRAS-mutant AML patient-derived xenograft (PDX) model, showing significantly improved leukaemia growth delay and event-free survival compared with single agent approaches. Assessment of leukemia burden in bone marrow and spleen during treatment further showed site-specific efficacy against circulating and spleen-resident blasts for both combinations. In summary, we report that our structure based-modelling approach can effectively identify novel, non-obvious, and well-tolerated RAFi combinations that are highly effective against in vitro and in vivo models, thereby suggesting alternative potential therapeutic strategies for high-risk RAS-mutant AML.

Chimeric antigen receptor T-cell (CAR-T) therapy targeting CD19 has transformed outcomes for children with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL), yet the influence of molecular subtype on outcomes remains unclear. We evaluated the impact of cytogenetic and molecular signatures on complete response (CR), overall survival (OS), and leukemia-free survival (LFS) after CD19 CAR-T therapy in eighty-six pediatric patients with R/R B-ALL treated with tisagenlecleucel. CR was assessed 30 days after infusion. Cytogenetic data were available for 84 patients and molecular profiling for 62. Survival analyses included 72 patients who received CD19 CAR-T as the sole cellular therapy. Seventy-seven patients achieved CR (89.5%). Pre-infusion bone marrow blasts of [&ge;]20% were associated with lower CR rates (53.8% vs 95.9%, p<0.0001) and significantly reduced OS and LFS (both p<0.0001). Among molecular markers, RAS mutations correlated with inferior OS (p=0.0222) and LFS (0.0402). In multivariate analysis, bone marrow blasts >20% and RAS mutations independently predicted inferior OS. Post CAR-T, CD19 negative relapses showed almost twice higher prevalence of RAS mutations (66% vs 37.5%). These findings highlight RAS mutations as a key molecular predictor of outcome after CD19 CAR-T therapy and suggest emergence of unique risk stratification for patients receiving CD19-targeting therapy. Key PointsO_LIRAS mutations independently predict unfavorable survival after CAR-T CD19 in pediatric B-ALL. C_LIO_LIRAS mutations increase risk of CD19 negative relapse after CAR-T CD19 therapy in pediatric B-ALL. C_LI

Nucleophosmin-1 (NPM1) mutations define a major molecular subtype of acute myeloid leukemia (AML) and is generally associated with favorable prognosis. However, the impact of myelodysplasia-associated mutations (MDSm+) on patient outcomes within this subgroup remains uncertain. We retrospectively analyzed 271 NPM1-mutated AML patients from three independent cohorts (SWOG, Fred Hutch, and Beat AML) to assess the prognostic significance of MDSm+ and its interaction with age. MDSm+ occurred in 17% of cases, most commonly involving SRSF2 and SF3B1. Although MDSm+ was associated with inferior overall survival compared to MDSm-in ELN2022 favorable-risk patients (HR 2.0, p=0.008), this effect was largely driven by worse outcomes in older patients ([&ge;]65 years) as older ELN22 favorable-risk patients had poor OS regardless of presence of MDSm+ compared to younger patients. After stratification of patients by age, there was not a significant difference between MDSm+ and MDSm-in either younger patients (HR 0.99, p=0.98) or older patients (HR 1.42, p=0.33). These findings indicate that MDSm+ in NPM1+ AML is not independently associated with adverse risk after adjusting for age and highlight the need for age-adjusted AML risk models.

Acute myeloid leukemia (AML) patients rarely have long first remissions (> 5 years) after standard-of-care chemotherapy, unless classified as favorable risk at presentation. Identification of the mechanisms responsible for long vs. more typical, short remissions may help to define prognostic determinants for chemotherapy responses. Using exome sequencing, RNA-sequencing and functional immunologic studies, we characterized 28 Normal Karyotype (NK)-AML patients with >5 year first remissions after chemotherapy (Long First Remissions, LFR) and compared them to a well-matched group of 31 NK-AML patients who relapsed within 2 years (Standard First Remissions, SFR). Our combined analyses indicated that genetic risk profiling at presentation (as defined by ELN 2017 Criteria) was not sufficient to explain the outcomes of many SFR cases. Single cell RNA-sequencing studies of 15 AML samples showed that SFR AML cells differentially expressed many genes associated with immune suppression. The bone marrow of SFR cases had significantly fewer CD4+ Th1 cells; these T-cells expressed an exhaustion signature and were resistant to activation by T-cell receptor stimulation in the presence of autologous AML cells. T-cell activation could be restored by removing the AML cells, or blocking the inhibitory MHC Class II receptor, LAG3. Most LFR cases did not display these features, suggesting that their AML cells were not as immunosuppressive. These findings were confirmed and extended in an independent set of 50 AML cases representing all ELN 2017 risk groups. AML cell-mediated suppression of CD4+ T-cell activation at presentation is strongly associated with unfavorable outcomes in AML patients treated with standard chemotherapy.

Preclinical cancer research requires robust model systems, especially for poor prognosis entities like acute myeloid leukemia (AML), a highly aggressive blood cancer. Here, primary tumor cells from 137 AML patients of all age groups were transplanted into immune compromised mice to generate patient-derived xenografts (PDX). From these, 23 models enable robust, virtually endless serial re-transplantation and are amenable to lentiviral genetic engineering (*PDX AML models). These models primarily originate from patients with highly aggressive, relapsed disease. Comprehensive genomic, transcriptomic, and epigenomic analyses confirmed that they replicate primary AML biology more faithfully than conventional cell lines. Notably, *PDX AML models include AML subgroups that are underrepresented or absent in existing model systems, such as cytogenetically normal or IDH1/2-mutant AML. They withstand freeze-thaw cycles, making them suitable for broad distribution and reproducibility across research institutions. Luciferase-based in vivo imaging enables real-time monitoring of tumor progression and treatment responses in preclinical trials. Surprisingly, long-term treatment, including repeated cytarabine therapy over a period of one year, showed a gradual reduction in leukemia cell proliferation, which decreased continuously after each treatment block. Collectively, our *PDX models represent a robust, versatile, and relevant platform that holds great promise to accelerate translational research for the benefit of cancer patients. Visual Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/677299v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1ead31eorg.highwire.dtl.DTLVardef@1ca702corg.highwire.dtl.DTLVardef@18a7137org.highwire.dtl.DTLVardef@edbe6_HPS_FORMAT_FIGEXP M_FIG C_FIG Key PointsO_LIWe present new robust AML PDX models covering subgroups for which no cell lines exist for use in various ex vivo and in vivo applications. C_LIO_LI*PDX models enable serial transplantation, genetic engineering and better representation of primary AML biology than cell lines. C_LIO_LIOne-year in vivo trials mimicking clinical chemotherapy showed surprising gradual decline in leukemia growth after each treatment block. C_LI

Interactions between acute myeloid leukemia (AML) and the bone marrow microenvironment (BMME) are critical to leukemia progression and chemoresistance. In the solid tumor microenvironment, altered metabolite levels contribute to cancer progression. We performed a metabolomic analysis of AML patient bone marrow serum, revealing increased metabolites compared to age- and sex-matched controls. The most highly elevated metabolite in the AML BMME was lactate. Lactate signaling in solid tumors induces immunosuppressive tumor-associated macrophages and correlates with poor prognosis. This has not yet been studied in the leukemic BMME. Herein, we describe the role of lactate in the polarization of leukemia-associated macrophages (LAMs). Using a murine AML model of blast crisis chronic myelogenous leukemia (bcCML), we characterize the suppressive phenotype of LAMs by surface markers, transcriptomics, and cytokine profiling. Then, mice genetically lacking GPR81, the extracellular lactate receptor, were used to demonstrate GPR81 signaling as a mechanism of both the polarization of LAMs and the direct support of leukemia cells. Furthermore, elevated lactate diminished the function of hematopoietic progenitors and reduced stromal support for normal hematopoiesis. We report microenvironmental lactate as a mechanism of AML-induced immunosuppression and leukemic progression, thus identifying GPR81 signaling as an exciting and novel therapeutic target for treating this devastating disease.