Akira Nishimura

NUTM1 rearrangement defines a significant subset of B-cell acute lymphoblastic leukemia (B-ALL), particularly in infants lacking KMT2A rearrangements, yet its underlying molecular characteristics remain poorly understood. Here, we establish that NUTM1-rearranged (NUTM1-r) leukemia is a discrete entity characterized by a unique transcriptional and epigenetic landscape, notably featuring global DNA hypomethylation, irrespective of the 5′ fusion partner. Functional interrogation of NUTM1 fusions reveals a dual oncogenic role: they drive commitment toward the B-lymphoid lineage while concurrently conferring potent leukemic stem cell properties. Strikingly, expression of a representative fusion, BRD9-NUTM1, is sufficient to induce serially transplantable B-cell progenitor, prepro–B-like leukemia in vivo, faithfully recapitulating the key molecular and immunophenotypic features of human NUTM1-r B-ALL. Mechanistically, NUTM1 fusions establish an aberrant chromatin state, marked by global enhancement of H3K27 acetylation and the creation of distinctive open chromatin regions that co-opt both B-lineage and stemness-related transcriptional programs, including those involving NF-κB and posterior HoxA genes. In stark contrast to resistant KMT2A-rearranged leukemias, NUTM1-r leukemic cells exhibit a profound sensitivity to chemotherapy. This vulnerability is mechanistically linked to the leukemia's dependence on active transcription. Our findings delineate the unique molecular profile of NUTM1-r leukemias, revealing specific vulnerabilities that rationalize their favorable clinical outcomes and suggest opportunities for modified therapeutic strategies.

X-linked lymphoproliferative syndrome type 1 (XLP1) is an inborn error of immunity caused by pathogenic variants in SH2D1A and is frequently complicated by Epstein-Barr virus (EBV)–associated lymphoproliferative disorders (LPDs). However, cases of LPD without EBV infection have been reported and remain poorly understood. We investigated tumorigenesis mechanisms through transcriptomic profiling and somatic variant analysis in tumor samples from six patients with XLP1. Pathogenic variants were identified in two: one developed two distinct LPDs harboring CARD11/GNA13 and MECOM variants, while the other carried IRF4, P2RY8, KRAS, and CCND3 variants. Transcriptome analysis of three tumors, compared with diffuse large B cell lymphoma from patients without an underlying immune defect, revealed a distinct expression profile. Gene Ontology analysis showed upregulation of adaptive immune response genes, including various IgH and TCR genes, suggesting polyclonal lymphocyte proliferation. Overall, LPD associated with XLP1 may originate from polyclonal lymphocyte expansion, either in the presence or absence of EBV infection, and subsequently progress to malignancy through somatic variants.

Lineage switching (LS) is the conversion of cancer cell lineage during the course of a disease. LS in leukemia cell lineage facilitates cancer cells escaping targeting strategy like CD19 targeted immunotherapy. However, the genetic and biological mechanisms underlying immune evasion by LS leukemia cells are not well understood. Here, we conduct a multi-omics analysis of patient samples and find that lineage-switched acute myeloid leukemia (LS AML) cells with KMT2A rearrangement (KMT2A-r) possess monocytic myeloid derived suppressor cell (M-MDSC)-like characteristics. Single-cell mass cytometry analysis reveals an increase in the M-MDSC like LS AML as compared to those of lineage-consistent KMT2A-r AML, and single-cell transcriptomics identify distinct expression patterns of immunoregulatory genes within this population. Furthermore, in vitro assays confirm the immunosuppressive capacity of LS AML cells against T cells, which is analogous to that of MDSCs. These data provide insight into the immunological aspects of the complex pathogenesis of LS AML, as well as development of future treatments.

Discovered >70 years ago by Ogden Bruton, X-linked agammaglobulinemia (XLA), characterized by recurrent bacterial infections, hypo/agammaglobulinemia, and peripheral blood B-cell deficiency, is among the best-established inborn errors of immunity (IEIs) and one of the most well-documented single types of IEIs, the incidence of which is estimated to be between 1:100,000 and 1:200,000. However, although the pathogenesis of XLA is well understood, several issues remain open for discussion. In this review, we describe several unresolved issues, including noncoding BTK variants, contiguous deletion syndrome, Helicobacter infection, noninfectious neurodegeneration, renal involvement, and malignancies. The primary treatment for XLA, immunoglobulin replacement therapy, administered either intravenously or subcutaneously, has remained unchanged since its discovery. Allogeneic hematopoietic cell transplantation has been successful in some XLA patients, but there are still few reports. However, it may be considered as a treatment option in the future. Given that XLA is one of the most common types of IEIs, resolving these issues is a priority.

Myeloid/natural killer (NK) cell precursor acute leukemia (MNKPL) has been described on the basis of its unique immunophenotype and clinical phenotype. However, there is no consensus on the characteristics for identifying this disease type because of its rarity and lack of defined distinctive molecular characteristics. In this study, multiomics analysis revealed that MNKPL is distinct from acute myeloid leukemia, T cell acute lymphoblastic leukemia, and mixed-phenotype acute leukemia (MPAL), and NOTCH1 and RUNX3 activation and BCL11B down-regulation are hallmarks of MNKPL. Although NK cells have been classically considered to be lymphoid lineage–derived, the results of our single-cell analysis using MNKPL cells suggest that NK cells and myeloid cells share common progenitor cells. Treatment outcomes for MNKPL are unsatisfactory, even when hematopoietic cell transplantation is performed. Multiomics analysis and in vitro drug sensitivity assays revealed increased sensitivity to l -asparaginase and reduced levels of asparagine synthetase (ASNS), supporting the clinically observed effectiveness of l -asparaginase.

KMT2A-rearranged infant acute lymphoblastic leukemia (ALL) represents the most refractory type of childhood leukemia. To uncover the molecular heterogeneity of this disease, we perform RNA sequencing, methylation array analysis, whole exome and targeted deep sequencing on 84 infants with KMT2A-rearranged leukemia. Our multi-omics clustering followed by single-sample and single-cell inference of hematopoietic differentiation establishes five robust integrative clusters (ICs) with different master transcription factors, fusion partners and corresponding stages of B-lymphopoietic and early hemato-endothelial development: IRX-type differentiated (IC1), IRX-type undifferentiated (IC2), HOXA-type MLLT1 (IC3), HOXA-type MLLT3 (IC4), and HOXA-type AFF1 (IC5). Importantly, our deep mutational analysis reveals that the number of RAS pathway mutations predicts prognosis and that the most refractory subgroup of IC2 possesses 100% frequency and the heaviest burden of RAS pathway mutations. Our findings highlight the previously under-appreciated intra- and inter-patient heterogeneity of KMT2A-rearranged infant ALL and provide a rationale for the future development of genomics-guided risk stratification and individualized therapy.

Purpose The purpose of our study was to compare the safety and efficacy of hematopoietic cell transplantation (HCT) using fludarabine (Flu)-based reduced intensity conditioning (RIC) with busulfan (BU) or melphalan (Mel) for primary immunodeficiency diseases (PID). Methods We retrospectively analyzed transplant outcome, including engraftment, chimerism, immune reconstitution, and complications in 15 patients with severe combined immunodeficiency (SCID) and 27 patients with non-SCID PID. The patients underwent Flu-based RIC-HCT with BU (FluBU: 7 SCID, 16 non-SCID) or Mel (FluMel: 8 SCID, 11 non-SCID). The targeted low-dose BU with therapeutic drug monitoring was set to 30 mg hour/L for SCID. Results The 2-year overall survival of all patients was 79.6% and that of patients with SCID in the FluBU and FluMel groups was 100% and 62.5%, respectively. In the FluBU group, all seven patients achieved engraftment, good immune reconstitution, and long-term survival. All five patients receiving umbilical cord blood transplantation achieved complete or high-level mixed chimerism and sufficient specific IgG production. In the FluMel group, six of eight patients achieved complete or high-level mixed chimerism. Viral reactivation or new viral infection occurred in one FluBU group patient and four FluMel group patients. In the non-SCID group, 10 of 11 patients (91%) who received FluMel achieved complete or high-level mixed chimerism but had variable outcomes. Patients with WAS (2/2 patients), NEMO deficiency (2/2 patients), and X-linked hyper IgM syndrome (2/3 patients) who received FluBU achieved complete or high-level mixed chimerism and long-term survival. Conclusions RIC-HCT with FluBU is a safe and effective strategy for obtaining high-level donor chimerism, immune reconstitution including B cell function, and long-term survival in patients with SCID. In patients with non-SCID PID, the results varied according to the subtype of the disease. Further prospective studies are required to optimize the conditioning regimen for non-SCID PID.

Pearson syndrome (PS) is a very rare and often fatal multisystem disease caused by deletions in mitochondrial DNA that result in sideroblastic anemia, vacuolization of marrow precursors, and pancreatic dysfunction. Spontaneous recovery from anemia is often observed within several years of diagnosis. We present the case of a 4‐month‐old male diagnosed with PS who experienced prolonged severe pancytopenia preceding the emergence of monosomy 7. Whole‐exome sequencing identified two somatic mutations, including RUNX1 p.S100F that was previously reported as associated with myeloid malignancies. The molecular defects associated with PS may have the potential to progress to advanced myelodysplastic syndrome .