Proinflammatory signaling is a hallmark of myeloproliferative neoplasms. Several studies have shown that monocytes are a major source of proinflammatory cytokines and that monocyte-derived fibrocytes play a pivotal role in the pathogenesis of myelofibrosis (MF). To further explore the role of monocytes in MF, we generated inducible NrasG12D/+Jak2V617F/+ (NJ) mice. Recipients transplanted with NJ bone marrow (BM) cells developed MF with an early onset of anemia and monocytosis. In vitro, NJ recipients' BM nucleated cells exhibited an increased quantity of CD45+CollagenI+ fibrocytes, which were mainly derived from the Ly6chigh monocytes. RNA sequencing identified a significant elevated expression of CD38 (a NAD+ hydrolase) in Ly6chigh monocytes from NJ mice, which results in a pronounced lower level of NAD+. In humans, CD14+ monocytes from patients with MF showed a significantly higher expression of CD38 than controls and monocytes from patients with polycythemia vera with grade 1 fibrosis had higher CD38 expression than those without fibrosis. Finally, boosting NAD+ via pharmacological CD38 targeting or NAD+ precursor supplementation inhibited the differentiation of fibrocytes in vitro and targeting CD38 can effectively prevent the onset of fibrosis in vivo. Collectively, our findings shed light on the role of CD38 in monocytes and suggest potential clinical applications such as the use of CD38 as a biomarker of fibrotic progression and the clinical utility of CD38 inhibition in patients with MF.

The evolutionary history of cancers is encoded in molecular patterns that provide critical insights into the mechanisms of tumor progression. However, reconstructing cancer lineages in patient tumors remains challenging, as conventional sequencing captures only static snapshots of an ongoing evolutionary process. DNA methylation at CpG sites is a heritable epigenetic mark that accumulates stochastic errors - termed epimutations - at rates far exceeding those of somatic DNA mutations. These epimutations serve as a 'molecular clock' and can be harnessed for retrospective lineage tracing. When applied at single-cell resolution, methylation-based lineage tracing enables the reconstruction of cancer phylogenies and provides a powerful framework for studying the dynamics of treatment resistance, cell-state heritability, and metastasis directly in human tumors. In this review, we outline the strengths and challenges of single-cell DNA methylation-based lineage tracing, highlight key insights gained from its application with an emphasis on hematological cancers where relevant, and discuss its future potential in advancing our understanding of cancer evolution.

Many patients receiving frontline tyrosine kinase inhibitors (TKIs) for chronic-phase chronic myeloid leukemia (CML-CP) experience inadequate disease control and/or adverse events (AEs) that impair quality of life. Treatments offering optimal efficacy, safety, and tolerability will support long-term therapy. In the primary analysis from the ASC4FIRST trial, a phase 3 randomized trial comparing asciminib with investigator-selected TKIs (IS-TKIs) in newly diagnosed CML-CP, asciminib demonstrated superior efficacy vs all IS-TKIs and vs imatinib in the imatinib stratum, meeting both primary objectives. In the secondary analysis (2.2 years' median follow-up), major molecular response (MMR) rate at week 96 was 74.1% with asciminib vs 52.0% with IS-TKIs (treatment difference, 22.4% [95% confidence interval (CI), 13.6-31.3]; 1-sided P< .001) and 76.2% with asciminib vs 47.1% with imatinib in the imatinib stratum (treatment difference, 29.7% [95% CI, 17.6-41.8]; 1-sided P< .001), meeting both key secondary objectives. MMR rate was 72.0% with asciminib vs 56.9% with second-generation (2G) TKIs (treatment difference, 15.1% [95% CI, 2.3-28.0]; 1-sided P< .05), suggesting possible clinical benefit, although the study was not designed to formally confirm statistical significance for this secondary end point. Safety/tolerability remained favorable with asciminib vs IS-TKIs. Dose reductions and interruptions, respectively, occurred with asciminib (18.5%; 46.5%), imatinib (23.2%; 47.5%), and 2G TKIs (54.9%; 63.7%). The hazard ratio for time to discontinuation of treatment due to AEs for asciminib vs 2G TKIs was 0.46 (95% CI, 0.215-0.997). With longer follow-up, asciminib continued to demonstrate a favorable benefit-risk profile over IS-TKIs and imatinib, supporting its potential as a treatment option for newly diagnosed CML-CP. This trial was registered at www.clinicaltrials.gov as NCT04971226.

Efficient derivation of transplantable hematopoietic stem cells (HSCs) from human pluripotent stem cells (hPSCs) is constrained by epigenetic silencing. Through a clustered regularly interspaced short palindromic repeats/Cas9 screen with a BCL11A-enhanced green fluorescent protein reporter, we identified the epigenetic reader SP140 as a suppressor of hematopoiesis. Transient genetic or pharmacologic inhibition of SP140 in hPSC-derived teratoma and embryoid body cultures promoted robust multilineage hematopoiesis and accelerated production of HSCs with serial transplantability and durable reconstitution in immunodeficient mice. Mechanistically, SP140 blockade unlocked transcription at endothelial-to-hematopoietic transition (EHT) loci through topoisomerase 1-dependent chromatin remodeling, activating key hematopoietic and stem cell programs. Transcriptomic analysis showed activation of these regulators upon SP140 inhibition, which was prevented by topoisomerase 1 blockade. Cleavage under targets and tagmentation profiling identified SP140 binding at EHT and HSC-specification gene loci. SP140's function as an epigenetic gatekeeper was conserved in diverse hPSCs and murine embryo models, where its downregulation enhanced physiological HSC emergence. Importantly, selective SP140 inhibition in a chemically defined, scalable protocol enabled rapid in vitro generation of bona fide human HSCs suitable for transplantation. These findings identify transient SP140 inhibition as an effective strategy to overcome epigenetic barriers and unlock clinically relevant HSC specification from hPSCs, advancing regenerative hematopoiesis and cell therapy.

Cancer develops through the interactions between cancer stem cells and components of the tumor microenvironment (TME). To model in vivo cancer stem cell-TME interactions and elucidate their functional consequences, we focused on myelofibrosis (MF), a stem cell-driven myeloproliferative neoplasm. We cocultured MF hematopoietic stem and progenitor cells (HSPCs) with normal donor endothelial cells (ECs) and mesenchymal stromal cells (MSCs) to investigate the consequences of interactions between malignant MF HSPCs and nonmalignant microenvironmental cells. This tricultivation system proved to be a simple and reproducible platform, which promoted malignant clone dominance and the persistence of MF HSPCs that recapitulate the MF phenotype upon transplantation into immunodeficient mice, including splenomegaly and marrow fibrosis. Transcriptional profiling revealed extensive reprogramming of not only the cocultured MF HSPCs, but also MSCs and ECs. Although numerous disease-relevant pathways were upregulated, the proinflammatory response stood out as a key consequence of MF HSPC-TME interactions. We validated these findings through quantitation of proinflammatory transcript upregulation and cytokine production. This human multicellular model system has proven useful in demonstrating the multidirectional interactions of MF HSPCs with TME cells that are essential for sustaining fully functional MF stem cells.

Leukemic stem cells (LSCs) in acute myeloid leukemia (AML) depend on oxidative phosphorylation (OXPHOS) sustained by fatty acid oxidation (FAO) and mitochondrial fusion (mitofusion). In this study, we demonstrate that microRNA-126 (miR-126) maintains LSC function by promoting B-cell lymphoma 2 (BCL-2)-dependent FAO, OXPHOS, and mitofusion, whereas its inhibition disrupts mitochondrial metabolism, induces mitochondrial fission (mitofission), and triggers apoptosis. Mechanistically, miR-126 stabilizes BCL-2 through the SPRED1/extracellular signal-regulated kinase axis, which upregulates CPT1B (FAO) and NRF2 (antioxidant response) while regulating mitochondrial dynamics through DRP1 phosphorylation (inhibiting mitofission) and MFN1/2 phosphorylation (enhancing mitofusion). miRisten, a CpG-conjugated anti-miR-126 oligonucleotide now in clinical trials (NCT07025564), synergized with venetoclax (VEN) to suppress FAO/OXPHOS, promote mitofission, and impair LSC homeostasis. In vivo, miRisten potentiated the VEN/azacitidine regimen, an US Food and Drug Administration-approved therapy for older or unfit patients with AML, significantly prolonging survival in patient-derived xenograft models. VEN/miRisten combination also reduced LSC burden and restored VEN sensitivity, establishing miR-126 inhibition as a transformative therapeutic strategy for AML.

Measurable residual disease (MRD) monitoring has become a critical component in the management of acute myeloid leukemia (AML), to inform prognosis, guide therapy, and serve as a key end point in clinical trials. The 2025 update of the MRD guideline provides a comprehensive and refined framework for MRD assessment, aligned with the European LeukemiaNet (ELN) 2022 genetic risk classification. Developed by members of the ELN AML MRD Working Party, the guidelines incorporate expert consensus determined through a 2-stage Delphi round. They address the clinical implementation of MRD methodologies, technical considerations, integration into clinical trials, and future directions. Importantly, MRD recommendations are tailored to individual prognostic and genetic subgroups. A new qualitative MRD response category, designated as optimal, warning, or high risk of treatment failure, has been introduced to facilitate contextual interpretation of the MRD burden and its clinical relevance. Notably, ultrahigh-sensitivity next-generation sequencing-based MRD assessment is now recommended for FLT3 internal tandem duplication-mutated AML after intensive chemotherapy and before allogeneic hematopoietic cell transplantation. A total of 56 recommendations were formulated, with 53 achieving a high level of consensus (≥90%). These updated guidelines represent a major step forward toward harmonizing MRD assessments in AML and enhancing its clinical utility across diverse treatment settings.

To prevent graft-versus-host disease (GVHD) in patients undergoing myeloablative allogeneic hematopoietic stem cell transplantation (alloHSCT), a calcineurin inhibitor plus methotrexate is routinely used. Early phase studies suggested improved outcomes with Orca-T, an allogeneic T-cell immunotherapy that uses purified donor regulatory T cells to prevent GVHD with significantly less immunosuppression. This phase 3 trial randomized adult patients (N = 187) with acute leukemias or myelodysplastic syndrome undergoing myeloablative conditioning to receive either Orca-T with tacrolimus or a conventional allograft with tacrolimus and methotrexate (Tac/MTX), using granulocyte colony-stimulating factor-mobilized peripheral blood from HLA-matched donors. The primary end point was survival free from moderate-to-severe chronic GVHD (cGVHD; cGFS). Using a stratified log-rank test, cGFS was significantly higher in the Orca-T arm than in Tac/MTX (hazard ratio, 0.26; 95% confidence interval, 0.14-0.47; P< .001). One-year estimates were as follows: cGFS was 78.0% with Orca-T vs 38.4% with Tac/MTX; cumulative incidence of moderate-to-severe cGVHD was 12.6% with Orca-T and 44.0% with Tac/MTX (Gray test P< .001); overall survival was 93.9% with Orca-T vs 83.1% with Tac/MTX (P = .12); GVHD-free and relapse-free survival was 63.1% and 30.9% in the Orca-T and Tac/MTX arms (P< .001), respectively; nonrelapse mortality (NRM) was 3.4% with Orca-T vs 13.2% with Tac/MTX (P = .03). Orca-T met the primary end point of improved survival free from cGVHD compared with Tac/MTX prophylaxis and should be considered a new therapeutic option with low toxicity for GVHD prophylaxis. Moreover, significantly less toxicity was observed with Orca-T patients, including fewer serious infectious complications and less NRM. This trial was registered at www.clinicaltrials.gov as NCT05316701.

Hemophagocytic lymphohistiocytosis (HLH) is an interferon gamma-driven hyperinflammatory syndrome with high morbidity and mortality. Identifying reliable prognostic biomarkers is challenging due to various predisposing conditions and triggers. C-X-C-motif ligand 9 (CXCL9) is a clinically validated biomarker and surrogate marker of interferon gamma-mediated inflammation. We aimed to identify the role of CXCL9 in predicting severe disease and death in adults with HLH using a multicenter retrospective cohort of consecutively hospitalized patients who underwent a clinical evaluation for HLH that included CXCL9 testing. Patients were classified as HLH if they met HLH-2004 and/or HScore criteria. Conditional inference decision trees and Cox regression models were used to identify which clinical variables associated with acute mortality in patients with HLH. Overall, 171 patients were reviewed, and 126 patients met HLH criteria. The median age was 55 years (interquartile range, 40-66), with 62% male and 51% White. CXCL9 was markedly elevated in patients with HLH. Unbiased decision tree modeling, incorporating all clinical laboratory values, identified only CXCL9 of >16 100 pg/mL as the optimal predictor of inpatient mortality. Cox regression models demonstrated that CXCL9 of >16 100 pg/mL was significantly associated with 90-day mortality when controlling for important covariates. This shorter time to death in the elevated CXCL9 subgroup remained significant even after subdividing patients into those with malignancy (n = 53) and nonmalignancy HLH (n = 73). Continuous increases in CXCL9 within the cohort strongly associated with greater mortality. CXCL9 is a novel clinical marker that identifies high-risk HLH independent of underlying disease and could be used to select patients for early and aggressive targeted immunomodulatory therapy.

Recent studies have reached opposing conclusions about whether clonal hematopoiesis (CH) is increased or decreased in patients with sickle cell disease (SCD). Given that CH is typically age-related, its presence in children with SCD could offer unique insights into early-life mutagenesis and disease-related stressors. We tested the primary and secondary hypotheses that children with SCD would have a higher prevalence of CH than age-, sex-, and race-matched children without SCD and that children with hydroxyurea would have a higher CH prevalence than children not treated with hydroxyurea. To address this, we conducted a cross-sectional study in 2 independent cohorts of children aged 0 to 18 years with SCD (N = 1025 and N = 1293, respectively) and a 2957-person matched comparison group. Using a highly sensitive, error-corrected sequencing assay capable of detecting CH at a variant allele frequency of ≥0.5%, we found that children with SCD have a significantly higher prevalence of CH than the comparison group (odds ratio [OR], 4.2; P = 7.4 × 10-13). In addition, CH was not associated with exposure to hydroxyurea therapy (OR, 0.76; P = .44).