Remarkable progress in the understanding of disease pathogenesis and treatment across hematologic malignancies has been achieved in the past 2 decades. Nevertheless, the reliable elimination of disease remains elusive for many cancers. Chronic lymphocytic leukemia (CLL) exemplifies the needs that must be addressed to close the gap between discovery science and the remaining clinical challenges. In CLL, targeted therapies have substantially prolonged survival and enabled long-term disease control for many patients. However, curative outcomes remain exceptional, particularly in high-risk groups such as those with TP53 disruption, dual resistance to Bruton tyrosine kinase and B-cell lymphoma 2 inhibitors, or transformation to aggressive lymphoma. Recent insights into the interconnection between cancer and immunity have positioned CLL as a model example of cancer-associated immunodeficiency, a realization brought into sharp focus by the severe acute respiratory syndrome coronavirus 2 pandemic during which patients with CLL were at extremely high-risk for infection and poor outcomes. Therefore, complications related to infections, autoimmunity, and secondary cancers continue to contribute substantially to morbidity and mortality, underscoring the need for research on immune dysfunction in CLL. Furthermore, pronounced heterogeneity in disease progression and therapeutic resistance highlight the need for mechanistic studies to clarify these distinct biological patterns. Advances in these areas not only hold the promise of curative therapy for broader patient subgroups in CLL but will also inform innovation in research on other cancers, particularly in establishing a molecular definition of disease and defining those interactions with the underlying and resultant immune deficiencies.

The benefit of extended phased (∼) HLA class I∼class III∼class II haplotypes in reducing the mortality after hematopoietic cell transplantation is unknown and requires information on functional class III variation. We identified a robust class III single-nucleotide polymorphism (SNP), rs915654, informative for mortality and relapse in 1436 patients and their haploidentical related donors through multivariable regression analysis of 26 candidate class III SNPs. Three-marker haplotypes, as defined by 1 class I locus, 1 class II locus, and rs915654 were determined in patients separately from donors. Inclusion of rs915654 into relapse and mortality models already containing patient HLA-E∼DRB1 and donor HLA-B∼DRB1 improved each model (likelihood ratio test P = .06 and P = .004, respectively, for relapse; P = .10 and P = .01, respectively, for mortality). The risks of mortality and relapse increased with decreasing numbers of favorable patient and donor markers. Retesting in an independent cohort of 1141 haploidentical transplants yielded similar results. The number of unfavorable markers additionally increased nonrelapse mortality. HLA-A∼C∼B∼DRB1∼DQB1 haplotypes were defined according to their expected numbers of favorable markers, and the theoretical utility for selecting donors was explored. In summary, extended HLA class I∼class III∼class II haplotypes influence the success of transplantation and inform the biology of the major histocompatibility complex in health and disease. The selection of haploidentical donors for future patients may be optimized with knowledge of donor HLA haplotypes.

The hallmark of heparin-induced thrombocytopenia (HIT) is the presence of immunoglobulin G (IgG) antibodies against platelet factor 4/heparin (PF4/H) complexes, typically detected by PF4/H enzyme-linked immunosorbent assay (ELISA); thus, negative ELISA results are commonly used to exclude this diagnosis. Here, we report a prevalent yet previously unrecognized subset of antibodies that are undetectable by PF4/H ELISA (ELISA-) but activate platelets in the PF4-dependent P-selectin expression assay (PEA+). In 11 patients with clinically confirmed HIT who tested positive in both PF4/H ELISA and platelet activation assays, ELISA-PEA+ antibodies accounted for 65% ± 19% of total platelet-activating IgG activity and coexisted with ELISA+PEA+ antibodies. Consistent with this finding, single-cell cloning from 7 patients with HIT identified 23 PEA+ antibody-producing B-cell clones, of which 17 were ELISA-, outnumbering the ELISA+ clones. Functionally, ELISA-PEA+ antibodies closely resembled ELISA+PEA+ antibodies: platelet binding and activation required exogenous PF4 and were inhibited by FcγRIIA blockade, high-dose heparin, or Fab fragments made from ELISA+PEA+ antibodies. Importantly, these antibodies induced thrombocytopenia in a humanized mouse model of HIT. Despite lacking PF4/H reactivity in ELISAs, they recognize PF4 on platelets and showed no appreciable binding to neutrophil-activating peptide-2, interleukin-8, or PF4 alone. Structurally, these antibodies were heterogeneous, with a subset sharing heavy-chain features with ELISA+PEA+ antibodies. Collectively, our findings demonstrate that ELISA-PEA+ antibodies are a common, previously unrecognized feature of HIT, with functional relevance, supporting the possibility that they play an important, perhaps even central, role in HIT pathogenesis. Defining their prevalence, kinetics, and clinical impact deserves high priority for further investigation.

Interpreting genetic variants in complex genes such as PIEZO1 remains challenging because of marked allelic heterogeneity, relative tolerance to missense variation, and overlapping clinical phenotypes. Gain-of-function variants in PIEZO1 cause dehydrated hereditary stomatocytosis (DHS1, or hereditary xerocytosis), a pleiotropic syndrome characterized by anemia of variable severity and iron overload. In this study, we provided and applied an integrative framework combining the American College of Medical Genetics and Genomics guidelines, quantitative in silico predictions, structural domain annotation, and detailed patient phenotyping to classify 2565 PIEZO1 variants. A Bayesian scoring system with weighted evidence and a composite predictive score enabled reclassification of nearly 1000 variants of uncertain significance and highlighted nonrandom clustering of pathogenic variants within functionally constrained domains, particularly the anchor, inner helix, and C-terminal domains. Genotype-phenotype correlation analysis in 176 in-house DHS cases identified 3 phenotypic clusters, ranging from classical DHS1 with severe hemolysis and iron overload to atypical or subclinical presentations, reflecting domain-specific pathogenic mechanisms. Overall, this reclassification of PIEZO1 variants, integrated with genotype-phenotype correlation analysis, improves diagnostic precision, supports genotype-guided patient management, and underscores the value of integrating structural and clinical data into interpretation of rare genetic variants.

Patients with relapsed/refractory (R/R) mantle cell lymphoma (MCL), especially those progressing after Bruton tyrosine kinase (BTK) inhibitor and/or chimeric antigen receptor (CAR) T-cell therapy and those with high-risk features, have poor outcomes. The bispecific antibody, mosunetuzumab, combined with the antibody-drug conjugate (ADC), polatuzumab vedotin (Mosun-Pola), targets CD20 and CD79b via independent cell-killing mechanisms. In this multicenter phase 2 study, patients with MCL who had received ≥2 previous lines of therapy, including a BTK inhibitor, were enrolled. Patients received outpatient fixed-duration mosunetuzumab subcutaneously (17 cycles), with cycle 1 step-up dosing to mitigate cytokine release syndrome (CRS), and polatuzumab vedotin (1.8 mg/kg IV) for 6 cycles. The primary end point was centrally assessed best objective response rate. A total of 42 patients with a median of 3 previous therapies were enrolled; 26% had previous CAR T-cell therapy. A number of patients had MCL with high-risk features (Ki-67 of ≥50%, 67%; blastoid/pleomorphic morphology, 38%; TP53 aberration, 48%). Objective response occurred in 88.1% of evaluable patients (95% confidence interval [CI], 74.4-96.0) and complete response in 78.6% (95% CI, 63.2-89.7). With a median follow-up of 15.9 months, median progression-free survival was 18.6 months (95% CI, 13.9 to not estimable). Consistent efficacy was observed in high-risk subgroups. CRS occurred in 42.9% of patients and was limited to grade 1/2 events. Mosun-Pola achieved high complete remission rates while maintaining a manageable safety profile in patients with R/R MCL exhibiting high-risk features. This is, to our knowledge, the first bispecific-ADC combination therapy study in MCL. This trial was registered at www.clinicaltrials.gov as #NCT03671018.

Fibroblast growth factor 23 (FGF23) is a phosphate-regulating hormone produced by osteocytes. In iron deficiency anemia (IDA) and in chronic kidney disease (CKD), FGF23 is also produced by erythroid cells. Recent studies have suggested that rising circulating FGF23 is negatively associated with erythropoiesis in IDA and CKD. However, the distinct contributions of bone- and erythroid-produced FGF23 to anemia in IDA remain unclear. Using the conditional deletion of Fgf23 in osteocytes (Fgf23Dmp1-cKO) and in erythroid cells (Fgf23HbB-cKO) in mice fed a control (Ctr) or an iron deficient (ID) diet, we first determined that in ID, osteocytes and erythroid cells are distinct sources of circulating intact FGF23 (iFGF23) and FGF23 cleaved peptides, respectively. We further show that erythroid-specific deletion of Fgf23 corrected anemia in ID mice, and overexpression induced anemia in Ctr mice unlike osteocyte-specific deletion or overexpression of Fgf23. Importantly, erythroid-specific deletion of Furin (FurinHbB-cKO), the enzyme responsible for FGF23 cleavage, led to increased production of iFGF23 from erythroid cells and aggravated ID-induced anemia. iFGF23 also dose-dependently blocked the differentiation of erythroid progenitors in culture triggering mitochondrial dysfunction leading to impaired erythropoiesis. These effects were fully suppressed by co-treatment with an FGFR1 inhibitor. Finally, erythroid-specific deletion of Fgf23 in an animal model of progressive CKD prevented the development of anemia of CKD. In aggregate, our results show that erythroid-expressed FGF23 is a negative regulator of erythropoiesis that contributes to anemia via direct paracrine FGFR1 activation in erythroid precursors.

The conversion of the inactive zymogen prothrombin to the active protease thrombin in the common pathway of the coagulation cascade is the molecular event responsible for the pathophysiology of hemostasis and thrombosis. The conversion entails 2 proteolytic cleavages at R320 and R271 by the prothrombinase complex composed of the enzyme factor Xa (fXa), the cofactor fVa, Ca2+, and phospholipids. A recent cryogenic electron microscopy (cryo-EM) structure revealed how cleavage at R320 generates the active intermediate meizothrombin in the first step of the activation pathway. Here we present the 3.8 Å resolution cryo-EM structure of a truncated form of meizothrombin (mzTΔF1) bound to fVa and fXa that reveals how the second cleavage at R271 generates thrombin. The cleavage is brokered by molecular contacts that involve mostly the protease domains of mzTΔF1 and fXa and largely validate the results from biochemical studies. The switch in cleavage site from R320 to R271 involves a significant reorientation rather than conformational transitions of the protease domain of mzTΔF1 that moves the guanidinium group of R271 more than 20 Å into the primary specificity pocket of fXa. The findings complete the cryo-EM structural analysis of prothrombin activation along the meizothrombin pathway and advance our molecular understanding of a reaction critical to the pathophysiology of blood coagulation.

Excess iron induces tissue toxicity in various conditions, including hereditary hemochromatosis (HH). Hepcidin, a liver-derived hormone encoded by the HAMP gene, plays a pivotal role in regulating systemic iron by mediating the degradation of ferroportin (FPN), the sole cellular iron exporter. Previous research found that the E3 ubiquitin ligase RNF217 is a key regulator of iron homeostasis by directly affecting FPN degradation; however, the role of RNF217 overexpression in iron-overload disorders such as HH is poorly understood. To address this question, we generated both global and intestine-specific Rnf217-overexpressing mice and then crossed these mice with hemojuvelin knockout (Hjv-/-) mice, a model for studying hemochromatosis. We found that both global and intestine-specific Rnf217 overexpression caused an identical rescue of the HH phenotype, implicating duodenal enterocytes as the main site where RNF217 overexpression exerts its beneficial effects. Moreover, we found that intestinal Rnf217 overexpression significantly reduced iron accumulation in the serum and in vital organs; importantly, these effects were not correlated with hepcidin levels. In summary, our findings demonstrate that intestinal RNF217 overexpression can directly suppress iron absorption by modulating FPN protein levels, bypassing hepcidin. This suggests a possible therapeutic strategy for iron-overload disorders, warranting further study to establish its clinical potential.

Antigen-specific T-cell immunotherapies are transforming the treatment landscape of hematologic malignancies. Neoantigen-specific therapies that exploit the ability of endogenous T-cell receptors (TCRs) to recognize tumor-derived peptides in an HLA-restricted context differ mechanistically from modalities employing chimeric antigen receptor T cells, which target surface antigens in an HLA-independent manner. In contrast to approaches targeting tumor-associated antigens, neoantigen-specific strategies offer more precise tumor selectivity and reduced off-target toxicity. Advances in immunogenomics, immunopeptidomics, and functional validation have accelerated the identification of both personalized and recurrent neoantigens, and high-resolution sequencing technologies have further facilitated the characterization of their cognate TCRs, which are currently being explored for developing TCR-engineered T-cell therapies. Early-phase clinical trials in hematologic malignancies demonstrate that neoantigen-specific strategies are safe and feasible across multiple hematologic cancers, with ongoing studies actively assessing the immunogenicity, clinical efficacy, and durability of these approaches. This review synthesizes recent preclinical and clinical advances in the discovery, validation, and therapeutic exploitation of neoantigen-specific strategies in blood cancers, highlighting translational insights for prioritizing immunogenic neoantigens. Emphasis is placed on identifying biological and technological barriers that limit the therapeutic efficacy of neoantigen-specific immunotherapies, with the goal of distilling actionable insights to guide their development in hematologic malignancies.

Cancer survivors experience long-term skeletal and hematopoietic complications that limit quality of life following chemotherapy (CTX), yet the mechanisms underlying these defects remain incompletely understood. Using a murine model of doxorubicin (DOX)-based leukemia induction therapy, we show that CTX induces inflammatory remodeling of the bone marrow (BM) niche. DOX treatment resulted in loss of arteriolar vasculature, blockade of mesenchymal stromal cell (MSC) differentiation, trabecular bone loss, and reduced niche capacity to maintain hematopoietic stem cells (HSCs). These defects were accompanied by aberrant immune activation within the BM, marked by increased interferon-γ (IFNγ) production by CD8⁺ T cells. Inhibition of IFNγ signaling partially restored arteriolar vessels and adipogenic differentiation. Moreover, combined IFNγ blockade and deferoxamine mesylate (DFM), which promotes vascular recovery, attenuated chemotherapy-associated skeletal damage. Consistent with these findings, paired BM samples collected at diagnosis and post-CTX from leukemia patients exhibited altered MSC lineage priming, upregulation of inflammatory pathways, and expansion of BM CD8⁺ memory T cells after treatment. Together, these findings implicate IFNγ-driven chronic inflammatory remodeling as a central mechanism of CTX-associated BM niche dysfunction and pinpoints inflammatory signaling as a potential target to preserve BM function and long-term tissue integrity.

Studies suggest that platelet-derived transforming growth factor (TGF)-β1 is critical to immune thrombocytopenia tolerance via regulatory T-cell (Treg) modulation, but their implausibly high TGF-β1 levels likely reflect ex vivo artifacts. We could not confirm platelet-derived TGF-β1-driven Treg deficiency using knockout mice; remission maintenance likely involves extra-platelet TGF-β1 sources.

Chimeric antigen receptor (CAR) T-cell therapies have transformed the treatment of B-cell malignancies, yet challenges including manufacturing delays, T-cell exhaustion, and limited persistence impede broader clinical success. Here, we report the single-day production of nonactivated CAR T cells engineered to secrete interleukin-18 (IL-18), a proinflammatory cytokine that enhances T-cell function. These nonactivated CART19-IL-18 cells (IL-18-secreting anti-CD19 CAR T cells) exhibit robust antitumor efficacy across xenograft models of lymphoma, leukemia, and pancreatic cancer. IL-18 expression enhances the functional advantages of naïve-like nonactivated CAR T cells, resulting in improved persistence, metabolic fitness, and resistance to exhaustion. Single-cell transcriptomic analysis revealed upregulation of IL7R, KLF2, and MCL1, alongside suppression of inhibitory checkpoint genes such as PDCD1, TOX, and HAVCR2. Metabolomic profiling demonstrated enhanced mitochondrial bioenergetics, with increased spare respiratory capacity and accumulation of α-ketoglutarate, malate, and spermine. Functional in vitro and in vivo profiling demonstrated enhanced per-cell cytotoxicity and in vivo durability. We complemented these studies with single-cell transcriptomic and metabolomic analyses to define CAR T-cell biological states beyond what is captured by xenograft tumor clearance. This IL-18-enhanced, activation-free CAR T-cell product offers a clinically actionable platform with the potential to reduce vein-to-vein time while improving product potency and persistence, providing a rationale for clinical testing in patients with tumors refractory to standard CAR T-cell therapy.