Traumatic Brain Injury (TBI) is the leading cause of death in children and adults aged 18-44. Despite its high prevalence and devastating consequences, there are currently few effective therapies that target the acute, life-threatening complications of TBI - particularly cerebral edema and intracranial hemorrhage (ICH). The blood-brain barrier (BBB) and regulation of vascular stability following injury are emerging as critical therapeutic targets. In this study, we evaluate the therapeutic potential of a first-in-class, freeze-dried platelet-derived biologic (FDPlts) in a murine model of TBI. FDPlt transfusion significantly reduces post-TBI ICH and restores cerebral vascular perfusion. Additionally, FDPlts attenuate BBB permeability, suppress intravascular leukocytosis, and mitigate neuroinflammation evidenced by decreased microglial activation, astrocyte reactivity, and macrophage infiltration. Transcriptomic profiling of cortical and hippocampal tissues reveals that FDPlts downregulate gene networks associated with inflammation and fibrosis, suggesting a role for FDPlts in the modulation of post-injury repair. Mechanistically, FDPlts are enriched in Angiopoietin-1, a key bioactive protein that signals through the Tie2 receptor pathway, a central regulator of endothelial stability. Inhibition of Tie2 exacerbates BBB permeability after TBI, an effect attenuated by FDPlt administration; implicating Ang-1 as a key mediator of FDPlts mediated BBB protection in TBI. The BBB plays a vital role in maintaining cerebral homeostasis, and its breakdown after TBI initiates harmful cascades of edema, inflammation, and neuronal injury. Our findings demonstrate, for the first time, that a dried, platelet-derived biologic can promote vascular repair and neuroprotection in TBI.

Lenalidomide, a maintenance treatment in multiple myeloma first-line therapy, increases the risk of secondary malignancies, including B-cell precursor acute lymphoblastic leukemia (B‑ALL). We present a comprehensive molecular characterization of 57 patients with lenalidomide-associated B-ALL (LenB-ALL), revealing three mutational subgroups: (1) TP53mt (30%), (2) IDH2mt (p.R140Q) (23%) and (3) other, including NRAS/KRASmt. Remarkably, IDH2 R140Q mutations were highly enriched in LenB-ALL compared to primary B-ALL (p<0.001). Furthermore, IKZF1 intragenic deletions - often subclonal and likely RAG-mediated - were observed in 54% (7/13) of IDH2mt LenB-ALL cases. IDH2 mutations were not restricted to the leukemic clone: they persisted during MRD-negative remission and were identified in lymphoid as well as myeloid cell populations using fluorescence-activated cell sorting and single-cell RNA sequencing. This indicates a preleukemic origin of the IDH2 mutation within the context of clonal hematopoiesis. Transcriptomic and DNA methylation analyses revealed a distinct gene expression profile and a DNA hypermethylation phenotype in IDH2mt LenB-ALL, including IDH2mt-specific as well as lenalidomide-associated features. We propose that lenalidomide promotes expansion of IDH2-mutated clonal hematopoiesis and, via IKAROS downregulation, induces a maturation arrest at the B-cell precursor stage. Subsequent genetic or epigenetic alterations render leukemogenesis independent of ongoing lenalidomide exposure. Altogether, these data define IDH2mt B-ALL as a distinct molecular subtype that is markedly overrepresented after lenalidomide treatment and highlight clonal hematopoiesis as a key contributing factor in the development of LenB-ALL.

Erythropoiesis, the process of red blood cell production, is highly dependent on iron uptake via transferrin and its receptor, transferrin receptor 1 (TfR1), but the mechanisms governing the proper recycling of TfR1 in relation to cellular iron demands remain elusive. Here, we identify human TMEM187, a Golgi transmembrane protein of unknown function, as a novel negative regulator of erythropoiesis. Lack of TMEM187 in a cell model initiates erythropoiesis without the normal induction protocol and accelerates iron uptake. Following the induction protocol, TMEM187 ablation leads to premature erythroid maturation, resulting in early phosphatidylserine ectopia and cell membrane fragility, hallmarks of cellular senescence that renders the cells susceptible to macrophage recognition and phagocytosis. In zebrafish embryos, tmem187 deletion leads to enhanced early erythropoiesis, although the phenotype is later compensated, whereas hematopoietic stem-cell expression of human TMEM187 in mice, which lack endogenously a homologous gene, resulted in compromised erythropoiesis and moderate anemia. Mechanistically, we demonstrate that TMEM187 interacts with RAB11 to restrain endosomal recycling, interfering with RAB11-GRAB association that activates RAB11. Consequently, TMEM187 modulates TfR1 recycling to the cell membrane to fine-tune iron uptake efficiency for erythropoiesis. Our findings reveal a novel modulatory pathway in which TMEM187 plays a crucial role in regulating erythroid differentiation, maturation, and senescence, providing a previously unexplored perspective of TMEM187's physiological function.

Mice lacking Tissue Factor Pathway Inhibitor (Tfpi-/-) succumb to embryonic lethality from excess thrombin production and associated cerebrovascular defects called glomeruloid bodies. A transgene producing hyperactivatable mouse protein C (hMPC) was bred into Tfpi+/- mice to determine if excess activated PC (aPC) would correct the cerebrovascular defects in Tfpi-/- embryos. Tfpi-/-/hMPC+ embryos survived to adulthood. Despite the rescue of embryonic lethality, hMPC reduced glomeruloid body numbers by only 36% and did not prevent fibrin deposition or disruption of the blood-brain barrier within glomeruloid bodies. However, there was decreased hypoxia and cellular death in Tfpi-/-/hMPC+ brains suggesting that cytoprotective effects of hMPC contributed to Tfpi-/- rescue. The glomeruloid bodies were completely resolved in Tfpi-/-/hMPC+ P10 pups revealing a distinct temporal effect of TFPI on embryonic cerebrovascular development. Bulk RNAseq of E15.5 brain tissue identified increased angiogenesis as the overwhelming biological process altered in Tfpi-/- brain. This included changes in genes encoding apelin, adrenomedulin, and UNC5b, which was consistent with abundant endothelial tip cells within glomeruloid bodies. The increased expression of these angiogenic genes was reversed by the hMPC transgene. These findings define TFPI as an essential inhibitor of thrombin generation during embryonic angiogenesis that acts temporally within or around developing cerebral vasculature in a manner that is not compensated for by other anticoagulant proteins. The findings emphasize the importance of blood coagulation proteases and regulation of their activity in diverse biological processes.

Radiotherapy is an established treatment for low-grade primary cutaneous B-cell lymphoma. Recommendations on its use differ internationally, which prompted our group to conduct the present analysis. Twenty-two institutions participated in this international study. Patient eligibility required a diagnosis of limited (T1/T2) primary cutaneous marginal zone or follicle center lymphoma treated with radiotherapy between 1995 and 2023. Data were collected retrospectively until February 2024 in the framework of the International Lymphoma Radiation Oncology Group. Overall, 535 patients were analyzed. Predominant locations were the head (40%) and trunk (36%). Radiotherapy had a median dose of 24 Gy in fractions of 2 Gy. Complete responses were seen in 91% at a median time of 3.6 months following radiotherapy. There was no statistically significant difference between treatments ≤4 Gy or >4 Gy for complete or overall response rates (p=0.077 and p=0.056). However, there was an inferior duration of local control with ≤4 Gy (5-year local control 73% ± 12% vs. 96% ± 2%; p<0.001). Radiation dose was the main prognostic factor in the univariate and multivariate Cox analysis; however, higher doses did not translate into an overall survival benefit. Toxicities rarely exceeded grade 2 but were more frequent in the >4 Gy group. Radiotherapy remains an effective treatment option for indolent skin lymphoma with low toxicities. High response rates are observed with low doses ≤4 Gy. In comparison to conventional doses, these treatments have a shorter duration of local control but a favorable toxicity profile.

Intensive chemotherapy is standard for AML but carries high risks of life-threatening complications, particularly in vulnerable patients. We aimed to compare the efficacy and safety of a low-dose chemotherapy (LDC) regimen for induction of AML. A randomized, multicenter, noninferiority trial was conducted in patients aged <18 years with AML. Patients received low-dose cytarabine, mitoxantrone or idarubicin, and G-CSF (LDC) or standard-dose induction chemotherapy (SDC) (cytarabine, daunomycin, and etoposide). All patients received post-remission consolidation with standard chemotherapy and/ or hematopoietic stem cell transplantation. The primary endpoint was to compare response rates between treatments. The secondary endpoints were to compare the outcomes, toxicity, and safety of the LDC and SDC regimens. The two treatment arms showed no significant differences in outcomes. Complete remission (CR/CRi) rates after induction were 95.1% and 95.3% in the LDC and SDC arms, respectively. Measurable residual disease < 0.1% after induction II was observed in 87.4% and 87.1% of patients in the LDC and SDC arms, respectively. Median time to neutrophil and platelet recovery was significantly shorter among patients receiving the LDC regimen. Patients in the LDC arm had a 4-year overall survival (OS) of 81.3% vs. 83.6% (P = .611) and a 4-year event-free survival (EFS) of 61.5% vs. 63.1% (P = .832). In conclusion, the LDC regimen was well tolerated and was associated with CR, EFS, and OS rates that were not inferior to those of patients treated with the SDC regimen. The trial was registered at Chinese Clinical Trial Registry (ChiCTR1800015883).

Transposable elements (TEs) are emerging regulators of hematopoiesis and leukemia, creating vulnerabilities exploitable for therapy. Recent evidence shows that TE reactivation induces innate immune signalling, DNA damage responses and dependence on Poly(ADP-ribose) polymerase (PARP)-mediated protection, enabling synthetic lethality with PARP inhibition even in homologous-recombination-proficient leukemias with epigenetic gene mutations. In this article, we highlight the biology underpinning this novel TE-PARP axis, its therapeutic implications and strategies to expand beyond HR-deficient cancers through rational combinations with immunotherapy and refined patient stratification.

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a bleeding disorder in which maternal antibodies target fetal and neonatal platelet alloantigens, most commonly human platelet alloantigen-1a (HPA-1a), resulting in fetal and neonatal thrombocytopenia severe enough to cause life-threatening organ bleeds, such as intracranial hemorrhage. Hemolytic disease of the fetus and newborn (HDFN) is an analogous disease caused by maternal exposure to fetal red blood cell (RBC) alloantigens, most commonly because of postpartum fetal maternal hemorrhage (FMH), that can be prevented by prophylactic administration of fetal RBC-specific antibodies. Unlike HDFN, the events that trigger FNAIT are unknown and can occur during first pregnancies, making FNAIT difficult to predict and prevent. Herein, we investigated the ability of in utero FMH to induce maternal alloimmunization to HPA-1a and cause FNAIT in a preclinical model. Transfusion of HPA-1a-positive platelets into wild-type (WT) mice in numbers representing moderate and severe FMH in humans induced production of equivalent levels of HPA-1a-specific antibodies in non-pregnant mice and mice pregnant with WT or HPA-1a-positive fetuses, causing FNAIT in the latter. Administration to pregnant females of the HPA-1a-specific monoclonal antibody RLYB212/mAb 26.4 prevented FMH-induced maternal alloimmunization to HPA-1a and FNAIT in genetically susceptible pups. In mice pregnant with HPA-1a-positive fetuses but not exposed to FMH, administration of RLYB212/mAb 26.4 did not cause FNAIT. Together, these findings identify in utero FMH as a potential trigger for maternal alloimmunization to fetal HPA-1a and provide proof of concept that prophylactic administration of HPA-1a-specific antibodies may safely and effectively prevent FMH-induced FNAIT in at-risk pregnancies.

The terms clonal monocytosis of undetermined significance (CMUS) and clonal cytopenia and monocytosis of undetermined significance (CCMUS) were introduced by the International Consensus Classification of Myeloid Neoplasms (ICC) to describe cases of clonal hematopoiesis (CH) and a concurrent monocytosis, that did not meet the diagnostic criteria of chronic myelomonocytic leukemia (CMML). To date, their practical relevance as clinicopathological entities at a population level has not been assessed. Here, we assess the prevalence, significance and natural history of CMUS and CCMUS amongst 431,531 UK Biobank participants through analysis of clinical, genomic and health outcome data. We find that CMUS with an absolute monocytosis and CCMUS are high-risk entities strongly associated with incident myeloid neoplasia (MN), cardiovascular and renal disease. Noting the overall higher monocyte counts in men and the low rate of progression of DNMT3A-CMUS, we show that amending the definition of CMUS/CCMUS to incorporate sex-specific monocyte thresholds and the exclusion of isolated DNMT3A mutations from the definition significantly strengthens the association with incident MN. Finally, given their association with poor outcomes, we develop MoSAIC, a machine learning classifier to infer the presence of SRSF2 mutations (associated with high MN risk) amongst individuals with monocytosis, based on complete blood count indices alone. We corroborate our findings in an independent cohort of 625,328 Danish primary care patients. Our findings underscore the clinical relevance of CMUS and CCMUS as distinct high-risk states within the spectrum of clonal hematopoiesis, and establish an evidence base to refine their diagnostic definition.

Immunotherapies, such as allogeneic hematopoietic cell transplantation and infusion of chimeric antigen receptor T (CAR-T) cells have significantly extended our therapeutic armamentarium against several hematological malignancies. Blocking negative regulators of immunity with immune checkpoint inhibitors has significantly improved the survival of patients with mainly solid tumors. Despite their beneficial effects, these therapies are also associated with severe, immune-mediated side effects. Here, we discuss biological similarities and differences of acute graft-versus-host disease (GVHD), cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), immune effector cell-associated hemophagocytic lymphohistiocytosis like syndrome (IEC-HS), immune effector cell-associated hematotoxicity (ICAHT), local immune effector cell-associated toxicity syndrome (LICATS), and immune-related adverse events after immune checkpoint inhibition (irAEs). Recent data have led to a better understanding of the role of myeloid cells and T-cells, including tissue-resident T-cells, in the pathophysiology of GVHD, CAR-T-cell associated immunotoxicities and irAEs. Further, we summarize approved, currently evaluated and potential future therapies for immune-mediated toxicities of cancer immunotherapies. This review will help to understand how therapeutic strategies target communalities of different side effects to overcome immune-mediated side effects of cancer immunotherapies.

Despite great progress in understanding the genomic basis of immature T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma (T-ALL) and acute leukemias of ambiguous lineage (ALAL), there are still cases that lack defining genetic markers, complicating risk stratification and limiting targeted therapeutic options. Recent studies have shown that enhancer hijacking drives oncogene activation in approximately half of T-ALL cases, with the BCL11B enhancer frequently involved. Here, we describe a subtype of leukemia with a distinct gene expression signature, and immunophenotype characterized by positivity for immature (CD38), myeloid (CD13), T-lymphoid (cytoplasmic (c)CD3, CD7), and B-lymphoid markers (CD19, CD79a, CD10). This subtype is defined by the t(14;16)(q32;q24) translocation, which places the FOXF1 gene and its antisense long noncoding RNA gene FENDRR under the regulatory control of the BCL11B enhancer, leading to their ectopic transcriptional activation. Common concomitant genetic lesions are loss-of-function alterations of GATA3, CDKN2A/CDKN2B deletion and activating JAK/STAT and NOTCH1 pathway mutations. Patients were predominantly children and adolescents/young adults (AYA) and experienced poor treatment outcome. High-throughput drug screening of 176 compounds demonstrated efficacy of combined BCL2-family proteins and JAK/STAT signaling inhibitors. Additionally, the clinical use of tyrosine kinase inhibitors in some of these cases showed therapeutic efficacy. Collectively, these findings identify BCL11B-enhancer mediated deregulation of FOXF1/FENDRR as a hallmark of a subtype of high-risk lineage ambiguous leukemia that is potentially amenable to targeted therapeutic intervention.

Hypofibrinogenemia reduces experimental venous thrombosis, but the impact on arterial thrombosis remains unknown. In a cohort of patients with congenital fibrinogen disorders, 19/264 (~7%) patients developed arterial thrombosis, including 4/41 (~10%) patients with hypofibrinogenemia. However, 0/8 patients with fibrinogen aC-region truncation mutations reported arterial thrombosis over 286 patient-years. To analyze the impact of hypofibrinogenemia and the fibrinogen aC-region on arterial thrombosis, two mouse models were employed: 1) wildtype mice treated with lipid nanoparticles encapsulating siRNA against fibrinogen (siFga) and 2) Fga270/270 hypofibrinogenemic mice expressing fibrinogen with a truncated aC-region. While siFga-treated hypofibrinogenemic mice developed occlusive carotid artery thrombi similarly to controls, Fga270/270 mice displayed suppressed carotid thrombosis following FeCl3 challenge, indicating loss of the aC-region but not hypofibrinogenemia alone reduces arterial thrombosis. To determine if protection from arterial thrombosis in Fga270/270 mice was linked to loss of aC-region-platelet glycoprotein VI receptor (GPVI) interaction, platelet GPVI was depleted by JAQ1 antibody administration. JAQ1-treated wildtype mice were protected from arterial thrombosis following 5% FeCl3 but not 10% FeCl3 challenge. Interestingly, JAQ administration suppressed arterial thrombosis in siFga-treated mice but did not enhance protection in Fga270/270 mice following 10% FeCl3 challenge. Our studies suggest the fibrinogen aC-region promotes arterial thrombosis in hypofibrinogenemic conditions.