The regulated secretion of von Willebrand factor (VWF) from Weibel-Palade bodies (WPBs) in endothelial cells is fundamental to hemostasis. This process relies on recruiting Rab GTPases and their effectors to the WPB membrane, with the guanine nucleotide exchange factor MAPK-activating death domain (MADD) playing a central role. Biallelic variants in MADD lead to a pleiotropic neurological and developmental disorder that can include bleeding abnormalities. This study investigates the impact of pathogenic MADD variants on VWF secretion using patient-derived endothelial cells. We isolated endothelial colony-forming cells (ECFCs) from 3 pediatric patients with biallelic MADD variants and unaffected heterozygous family members. All patients exhibited low VWF plasma levels (22-30 IU/dL). Proteomic analysis of patient-derived ECFCs revealed an absence of MADD peptides, reduced VWF, and downregulation of proteins involved in the exocytotic machinery, including Rab3D and the Rab3/27 effector Slp4-a. Functional assays demonstrated diminished Rab27A and Rab3D activity and their failure to localize to WPBs in patient cells. Biochemical and live-imaging studies showed that histamine-induced VWF and VWF propeptide secretion were significantly reduced in patient cells due to delayed and reduced degranulation of WPBs. Our findings demonstrate the critical role of MADD in maintaining the secretion competence of WPBs and the magnitude of VWF secretion by regulating the recruitment of the endothelial exocytotic machinery. This study highlights the in vivo significance of WPB exocytosis in maintaining plasma VWF levels and establishes MADD as the first causal gene for quantitative von Willebrand disease in patients without pathogenic VWF variants.

The treatment landscape of B-cell non-Hodgkin lymphomas is rapidly evolving. However, few advances have occurred in marginal zone lymphoma (MZL) with a single FDA-approved agent impacting the treatment landscape. Multiple factors are associated with this slower pace of progress, with a lower MZL incidence representing a significant factor. Pivotal randomized indolent lymphoma clinical trials analyzed MZL subsets without the appropriate power to capture differences between treatment arms. Furthermore, the current Lugano Classification may not fully capture the presentation or treatment responses of some subtypes, preventing access to clinical trials and limiting an efficacy assessment across the disease spectrum. Thus, current MZL treatment is largely informed by single-arm studies with relatively empiric treatment sequencing among available agents. While frontline strategies in early- and advanced-stage MZL can achieve prolonged disease control, few options exist in the relapsed/refractory setting capable of achieving similar results. Emerging data demonstrate the encouraging efficacy of CD3xCD20 bispecific antibodies and antibody-drug conjugates in achieving deep responses, as well as the potential of circulating tumor DNA in risk stratification and molecular response monitoring. Compounding all these considerations, it is essential to recognize MZL as a heterogeneous group of diseases characterized by unique biology, clinical presentation, treatment response, toxicity, and survival. Nonetheless, a common characteristic across MZL subtypes is their general indolent disease course, emphasizing the need to incorporate patient-centered assessment in clinical trials to better inform the decision-making process.

Epcoritamab and glofitamab are CD20-directed bispecific antibodies (BsAbs) approved in the United States for relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL). Limited data exist for patients treated outside of trials. Patients with R/R DLBCL receiving commercial epcoritamab or glofitamab between 1 January 2023 and 15 October 2024 were collected from 21 United States institutions. Among 245 patients, 156 received epcoritamab and 89 received glofitamab, 113 were refractory to front-line therapy, 40 had MYC and BCL2 and/or BCL6 rearrangements, 147 received prior chimeric antigen receptor T-cell therapy, and 174 patients would have been ineligible for registrational trials. The overall response rate (ORR) for epcoritamab and glofitamab was 51% (23% complete response, [CR]) and 53% (30% CR), respectively. Median progression-free survival (PFS) was 2.6 months (95% confidence interval [CI], 2.0-3.8 months), and median overall survival (OS) was 7.8 months (95% CI, 6.2-11.0 months). The 6-month PFS was 36% (95% CI, 30-44) and the 6-month OS was 60% (95% CI, 54-67). Both trial ineligibility and undetectable CD20 pre-BsAbs portended shorter PFS and OS. Of 17 individuals with paired biopsies, 15 (88.2%) lost CD20 expression after BsAbs with a median time to progression of 3.7 months. This analysis including patients with R/R DLBCL shows the ORR to CD3/CD20 BsAbs was comparable to pivotal trials, although PFS and OS were lower. Baseline undetectable levels of CD20 were associated with poor outcomes. These results demonstrate the activity of BsAbs in R/R DLBCL, and underscore the importance of target antigen expression.

Acute myeloid leukemia (AML), an aggressive hematological malignancy, is driven by oncogenic mutations in stem and progenitor cells that give rise to AML blasts. Although these mutations are well characterized, their impact on healthy hematopoiesis, those blood cells exposed to AML but not mutated, has not been well characterized. Because the marrow is the major site for granulopoiesis, neutrophils are heavily influenced by AML pathobiology. Indeed, most patients with AML report neutropenia, rendering them susceptible to infections. However, because AML studies use peripheral blood mononuclear cells devoid of neutrophils, the characterization of neutrophil dysfunction remains poorly understood. To investigate AML-exposed neutrophils, a preclinical AML mouse model in which primary leukemic cells were transplanted into nonirradiated neutrophil reporter (Ly6G-tdTomato; Catchup) hosts was used. Neutrophils could not completely mature, suggesting impaired granulopoiesis. Single-cell transcriptomics of AML-exposed neutrophils revealed higher inflammation signatures and expression of CD14, an inflammatory marker. To address the factors contributing to this biology, an ex vivo cytokine screen was performed on marrow neutrophils, and it identified that nuclear factor κB signaling drove CD14 expression. AML-exposed neutrophils displayed widespread chromatin remodeling, and de novo motif discovery predicted increased binding sites for CCAAT enhancer-binding proteins and interferon regulatory factors. Moreover, AML-exposed neutrophils inhibited T-cell proliferation, highlighting their immune-suppressive capability. Finally, a similar biology of immature, inflammatory neutrophils was found in patients with AML, again indicating dysregulated granulopoiesis. Collectively, these data show that AML-associated inflammation alters neutrophil granulopoiesis, impairs neutrophil function, and drives immunosuppression, thereby contributing to patient susceptibility to infection.

Hematologists have a significant role in the diagnosis and management of light-chain amyloidosis and are frequently involved in the diagnosis of transthyretin and other more rare types of amyloidosis. Recent advances in diagnostic techniques and therapies are dramatically improving patient prognosis. Radionuclide imaging methods are emerging as a highly specific and noninvasive way to diagnose, quantify, and monitor organ involvement representing a major advance in amyloidosis management.

Advanced mycosis fungoides (MF) and Sézary syndrome (SS) have a poor overall survival (OS) of <5 years. Studies have found the current staging (IA-IVB) is inadequate for risk stratification. The PROCLIPI (Prospective Cutaneous Lymphoma International Prognostic Index) study was launched in 2015 at 46 international expert MF/SS centers, prospectively collecting predefined data sets in patients with newly diagnosed MF/SS, to determine a cutaneous lymphoma IPI (CLIPI). Five hundred fifty-two patients with advanced stage MF/SS were recruited. The 5-year OS was 50.0% for stage IIB, 64.8% for stage IIIA, 43.9% for stage IIIB, 50.8% for stage IVA1, 25.9% for stage IVA2, and 36.9% for stage IVB. Factors at diagnosis associated with a significantly worse survival were N3 status (P < .001), age >60 years (P < .001), raised serum lactate dehydrogenase (P = .005), and large-cell transformation in skin (P = .006). Modeling these 4 independent risk factors into a CLIPI found that there was a worse OS in high- vs low-risk (P < .001), high- vs intermediate-risk (P = .002) and intermediate- vs low-risk (P = .010) groups. Five-year OS was 63.3%, 44.7%, and 18.3% in the low-, intermediate-, and high-risk groups, respectively. In this advanced stage cohort there was a low 5-year survival and increasing stage was not associated with worsening survival. The use of CLIPI to stratify patients into risk groups has the potential to improve outcomes and aid optimal treatment selection. This trial was registered at www.ClinicalTrials.gov as #NCT02848274.

Deficiency of factor VIII (FVIII) causes hemophilia A (HA), and excess FVIII function increases venous thromboembolic risk. The phenotypic consequences of aberrant FVIII function underscore the importance of understanding mechanisms that downregulate activated FVIII (FVIIIa) to inform disease pathology and therapeutic drug design. Spontaneous A2-domain dissociation and activated protein C (APC) proteolysis are established mechanisms of FVIIIa inactivation. However, we know very little about how FVIIIa binding interactions with FIXa and FX affect FVIIIa inactivation in vivo. Here, we investigate this using recombinant FVIIIa variants to probe A2-domain dissociation (FVIIIa-D519V,E665V) and APC cleavage (FVIIIa-R336Q,R562Q), or both (FVIIIa-R336Q,R562Q/D519V,E665V), in biochemical assays and in HA mouse injury models. We found that FIXa binding to FVIIIa stabilized the A2 domain and increased the contribution of APC to FVIIIa inactivation. Additional studies using individual APC cleavage site variants (FVIIIa-R336Q and FVIIIa-R562Q) demonstrated that FIXa and FX can protect FVIIIa from APC cleavage at Arg562 and Arg336, respectively, in a manner that is incomplete in vivo. Data also demonstrate that APC inactivation of FVIIIa exceeds FVIII, suggesting differential APC recognition of FVIIIa relative to FVIII. Hemostatic studies of FVIII variants with altered inactivation demonstrated that both A2-domain dissociation and APC cleavage contribute to in vivo FVIIIa regulation. Specifically, stabilizing the A2 domain, inhibiting APC cleavage, or both, improved potency 2.4-, 4.8-, and >10-fold, respectively, over wild-type FVIII in a mouse hemostatic assay. Data support that both mechanisms of FVIIIa inactivation and FIXa interactions could be leveraged to enhance FVIII function for therapeutic benefit.

Tumor inflammation-associated neurotoxicity (TIAN) was recently proposed as a unique complication of immunotherapy in patients with brain tumor. Here, we report a first comprehensive characterization of TIAN in patients with central nervous system (CNS) lymphoma (CNSL) treated with CD19-directed chimeric antigen receptor (CD19-CAR) T cells. TIAN occurred in 10 of 56 (17.9%) patients with CNSL, with clinical onset at a median 3.5 days (range, 1-9) after CD19-CAR T-cell infusion. It was less frequently associated with cytokine release syndrome (60% vs 100%; P = .009) than immune effector cell-associated neurotoxicity syndrome (ICANS). Although symptoms were usually transient and fully reversible, TIAN was associated with a fatal outcome in 1 patient. Larger CNS tumor volume at baseline allowed the identification of patients at risk for TIAN (area under the curve, 0.847; P = .002). Maximizing Youden J statistics, a discriminatory tumor volume threshold of >3.4 cm3 was determined, which carried 87.5% sensitivity and 80.5% specificity. TIAN correlated with higher overall response rates to CD19-CAR T cells (90% vs 52%; P = .036) and improved progression-free survival (hazard ratio, 0.22; 95% confidence interval, 0.07-0.61; P = .006) on multivariate Cox proportional hazard regression. Postmortem histopathological evaluation of a TIAN lesion revealed a dense macrophage population with central necrosis and peripheral reactive gliosis, accompanied by loss of white matter and intracytoplasmic myelin in foamy macrophages. Collectively, our work supports TIAN as a localized on-tumor, on-target neurotoxicity syndrome, closely related to preexisting CNSL lesions and distinct from ICANS. CNS tumor volume at baseline may allow to identify patients at risk and may guide management.

Hematopoietic stem cells (HSCs) are responsible for sustaining the hematopoietic system throughout life, and their functional decline contributes to hematological disorders and organismal aging. Understanding the molecular mechanisms that govern HSC function is critical for developing interventions for treating and preventing aging-related diseases. Here, we show that DCAF8, a substrate recognition component of Cullin-RING E3 ubiquitin ligases, is highly expressed in HSCs and undergoes a progressive decline with age. Loss of DCAF8 in mice results in impaired function in HSCs, characterized by increased number yet decreased self-renewal capacity, which associates with cellular senescence and elevated DNA damage. Mechanistically, DCAF8 mediates the degradation of dedicator of cytokinesis 11 (DOCK11), a guanine nucleotide exchange factor for CDC42. In the absence of DCAF8, DOCK11 accumulates, leading to elevated CDC42 activity and consequential loss of polarity of HSCs. Knocking out Dock11 mitigates the senescence, DNA damage, and self-renewal defects of Dcaf8-/- HSCs. This study highlights a critical role of DCAF8 in preventing HSC senescence via the DOCK11-CDC42 axis and suggests potential therapeutic targets for preventing functional decline in HSCs.

The megakaryocytic (MK)-specific immunoreceptor G6b-B plays an essential role in MK development. Because germ line loss-of-function mutations of G6b-B in humans and its deletion in mouse models lead to thrombocytopenia and a myelofibrosis-like clinical phenotype (MF-MPIG6B), we explored the role of G6b-B in patients with myelofibrosis (MF) due to a myeloproliferative neoplasm (MPN) with thrombocytopenia (MPN-MF-T). We demonstrated that MKs generated from mononuclear cells (MNCs) from a patient with MF-MPIG6B as well as patients with MPN-MF-T failed to express GATA binding protein 1 and G6B and possessed a protein pattern expression characteristic of MKs primed for inflammation rather than platelet production. MNCs from patients with MPN-MF-T also generated fewer MK-biased hematopoietic stem cells and greater numbers of small cytoplasmic immature MKs (CD41+CD42-G6B-) as compared with MNCs from patients with nonthrombocytopenic MPN-MF (MPN-MF-NT). Plasma levels of transforming growth factor β1 (TGFβ1) and chitinase-3-like protein (CHI3L1) also known as YKL-40, which were shown to arrest normal MK maturation, were elevated in the patients with MF-MPIG6B. Although TGFβ1 plasma levels were similarly elevated in patients with MPN-MF-T and MPN-MF-NT, tumor necrosis factor α (TNFα) and YKL-40 levels were upregulated to a greater extent in patients with MPN-MF-T than those with MPN-MF-NT. Moreover, we identified a reciprocal positive regulatory loop involving TGFβ1 and YKL-40 in MF MKs. These findings indicate that impaired MK maturation, and reduced G6B expression lead to the predominance of proinflammatory MKs, which produce factors that further arrest MK development in patients with MF-MPIG6B and MPN-MF-T patients. This trial was registered at www.clinicaltrials.gov as #NCT03895112.

We developed an allogeneic matched donor CD19 chimeric antigen receptor (CAR) product (CAR-donor lymphocyte infusion [DLI]) for adult patients with B-cell acute lymphoblastic leukemia (B-ALL) after failure of allogeneic stem-cell transplantation (allo-SCT). We evaluate the risks and benefits of pre-CAR-DLI lymphodepleting chemotherapy (LD) and the efficacy of repeat CAR-DLI dosing per conventional DLI protocols. Primary outcomes were toxicity and feasibility of CAR-DLI manufacture; secondary outcomes included CAR-DLI engraftment, expansion, and persistence. A total of 17 allo-SCT donors received leukapheresis and 14 patients with B-ALL (median age, 43 years) received infusion. Median disease burden at registration was 50.5% bone marrow blasts (range, measurable residual disease [MRD] to 100%). Patients 1 to 7 received CAR-DLI alone (CAR-DLI-alone); patients 8 through 14 received CAR-DLI and LD with fludarabine/cyclophosphamide (CAR-DLI+LD). CAR-DLI+LD vs CAR-DLI-alone was associated with superior peak CAR-DLI engraftment (93 134 vs 8010 copies per μg genomic DNA [gDNA]), expansion (858 101 vs 39 038 copies per μg gDNA per 28 days) and persistence (median, 197 vs 32 days). CAR-DLI+LD was not associated with more immunotoxicity than CAR-DLI-alone, and graft-versus-host disease (GVHD; grade 1, skin) affected only 2 of 14 patients (14%). CAR-DLI+LD vs CAR-DLI-alone conferred superior event-free-survival and overall survival at 12 months (57% vs 29%; 83% vs 29%). Repeat CAR-DLI dosing was administered to 8 of 14 (57%) patients with morphological/MRD+ relapse, but with minimal engraftment/expansion or toxicity/efficacy. CAR-DLI+LD has a tolerable safety profile without significant GVHD and is associated with significantly better outcomes than CAR-DLI-alone. Repeat CAR-DLI dosing beyond dose 1 was not found to be effective in this analysis. This trial was registered at www.clinicaltrials.gov as #NCT02893189.

The bone marrow microenvironment is intimately linked to the biology that underpins the development and progression of multiple myeloma. However, the complex cellular and molecular features that form bone marrow niches are poorly defined. Here, we used subcellular spatial transcriptomics to profile the expression of 5001 genes in human bone marrow in the context of multiple myeloma. Using this approach, we explored the plasma cell and stroma ecosystem in bone marrow trephine biopsy specimens (herein referred to as trephines) from 21 individuals, including 7 with premalignant disease and 10 with newly diagnosed multiple myeloma. Using spatial transcriptomics in conjunction with an optimized trephine biobanking methodology, we could resolve major components of the human bone marrow microenvironment and reliably characterize distinct plasma cell populations in samples from healthy, premalignant disease and active myeloma. When plasma cells were visualized in the context of location, we detected spatially restricted subpopulations of plasma cells in 5 of 10 newly diagnosed myeloma trephines. Surprisingly, the composition of hematopoietic and stromal microenvironments varied significantly between newly diagnosed myeloma trephines. Furthermore, these differences in microenvironments were also observed within trephines that had spatially restricted plasma cell subpopulations. Thus, these data are not consistent with the hypothesis that a universal bone marrow microenvironment supports the expansion of malignant plasma cells in myeloma. Instead, we propose that myeloma subpopulations form distinct microenvironments and can vary both between patients and spatial locations.

Venous thromboembolism (VTE) affects ∼1 in 200 hospitalized children. The diagnosis of pulmonary embolism (PE), the most severe clinical presentation of VTE, has increased dramatically by ∼200% over the past 2 decades, disproportionately affecting adolescents, and is associated with adverse long-term post-PE sequelae. Nevertheless, the management of pediatric PE remains highly variable. This review focuses on significant advances in pediatric PE, with a focus on published studies within the past decade. Using a representative case, we: (1) summarize existing risk prediction tools for acute pediatric PE, and a shift in clinical practice in the management of acute PE with the implementation of pediatric PE response teams and multidisciplinary decision-making for severe pediatric PE, (2) describe recently completed clinical trials of anticoagulation in children and adolescents, and ongoing work to elucidate the appropriate duration of therapy for children and adolescents with PE, and (3) review advances in understanding post-PE syndrome, and the need for continued refinement of evaluation tools and management approaches. Many unanswered questions remain despite the significant advances in pediatric thrombosis over the past decade.

Chronic lymphocytic leukemia (CLL) is the most common chronic blood cancer in adults. Active NOTCH signaling in CLL is associated with poorer prognosis. Importantly, patients with CLL with NOTCH1 noncoding mutations in the 3' untranslated region (3'UTR) manifested with a more aggressive disease course even compared with those with mutations in the NOTCH1 coding region. Here, we comprehensively characterize a cryptic splice acceptor site in the 3'UTR of the NOTCH1 gene being converted into a stronger site. The functional consequences of the resulting NOTCH1 protein variants depend on the exact localization of the splice site, the used open reading frame, and the appearance of the next stop codon. The most frequent 3'UTR mutation (g.139390152, A>G) generates a novel NOTCH1 protein, lacking the PEST domain but expressing an altered C terminus consisting of 68 amino acids. Mechanistically, we demonstrate that this splice variant (NOTCH1 152) is transcriptionally less active and dysregulates the regular ubiquitination-dependent degradation of the wild-type NICD (NOTCH1 intracellular domain) in trans. Thus, the NOTCH1 152 variant acts as a "sponge" protein in a novel mechanism of oncogenic NOTCH signaling activation, explaining the detrimental disease outcome of patients with CLL with noncoding NOTCH1 mutations. We propose that the detection of NOTCH1 152 protein by specific antibodies is a useful prognostic marker for patients with CLL.

Chimeric antigen receptor (CAR) T cells exhibit high response rates in B cell malignancies, but most patients eventually relapse. A key mechanism of treatment failure is the loss or downregulation of tumor antigen expression, yet strategies to modulate cell surface levels of CAR T cell targets remain largely unexplored. Here we identify B cell maturation antigen (BCMA), a central CAR T cell target in multiple myeloma (MM), as a highly short-lived protein that undergoes K48-linked polyubiquitylation at the plasma membrane, leading to its p97-dependent degradation via the ubiquitin-proteasome system (UPS). This previously unprecedented mechanism of plasma membrane protein regulation enables significant enhancement of BCMA expression via proteasome inhibitors (PI). The clinically approved PI carfilzomib (CFZ) significantly enhances the efficacy of BCMA-directed CAR T cells against both PI-sensitive and refractory MM cells in vitro and in vivo. Notably, treatment of ten patients with CFZ under the compassionate use CarCAR protocol - after relapse following BCMA CAR T cell therapy - resulted in increased BCMA expression in all patients. However, clinical responses were observed only in those with residual and/or expanding CAR T cells, suggesting restored CAR T cell function. These findings provide a rationale for the use of CFZ treatment in relapsed or refractory MM following BCMA CAR T therapy, advocate for future trials combining CFZ with BCMA CAR T cells and provide a framework for exploring UPS-dependent degradation of other immunotherapy antigens.

The contact system includes factor XII (FXII), FXI, prekallikrein (PK), and high-molecular-weight kininogen (HK), and has received increased interest as a potential target in immunothrombotic and inflammatory diseases. This system activates 2 distinct pathways, the intrinsic pathway of coagulation via cleavage of FIX, and inflammation via HK cleavage resulting in bradykinin (BK) generation. HK is central to the function of both arms of the system as a substrate for plasma kallikrein and critical cofactor, which forms interactions with cell receptors and activators. Both FXI and PK circulate in complex with HK and both can be cleaved by activated FXII. Reciprocal activation and continuous consumption of PK and FXII is a feature of the contact system. On endothelial cells, PK and FXII become activated but only in the presence of secreted receptor for the globular domain of C1q and Zn2+ ions. A second mechanism exists on endothelial cells whereby prolylcarboxypeptidase activates the PK-HK complex to generate BK in an FXII-independent manner. On platelets, FXI can be cleaved by thrombin, but only in the presence of secreted polyphosphate. This review explores the 3-dimensional structure of the contact factors and examines the molecular mechanisms underlying contact activation. We focus on conformational changes that expose cleavage sites and exosites in FXII, PK, and FXI. We also discuss contact factor protein-protein interactions, recognition of polyanions, and the role of HK and Zn2+ in contact system assembly.