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Background: Acute erythroid leukemia (AEL) or AML-M6 predominantly affects older adults and is rare in childhood. Compared with other AML subtypes, AEL remains relatively understudied because of its rarity. We established LS-CHM, a novel AEL cell line derived from the ascitic fluid of a patient with congenital leukemia. Interestingly, leukemic cells persisted in the ascitic fluid even after successful eradication from the bone marrow and extramedullary sites. Method: Leukemia cells from the ascites fluid exhibited robust proliferation in culture independent of cytokine requirement and were further characterized by flow cytometric immunophenotyping, cytogenetics, cell cycle and doubling time analysis, colony formation, genome and RNA sequencing, myeloid gene next generation sequencing, and cytotoxicity analysis. Results: LS-CHM displayed CD36, partial CD235a, CD31, CD43, and CD71 expression and demonstrated in vitro robust growth and high sensitivity to chemotherapeutic agents. A PDX mouse model showed development of leukemia. Genomic analysis revealed a frameshift BCOR mutation in the absence of additional mutations and downregulated TP53 expression with an exonic non-deleterious mutation. RNA sequencing of LS-CHM cells revealed upregulation of two cohesin complex genes, RAD21 and SMC3, whose high levels are associated with hematopoietic stem cell differentiation into erythroid lineage. Conclusions: LS-CHM represents the first congenital AEL-derived cell line, in contrast to the predominantly adult-origin and often secondary erythroid leukemia cell lines available currently. Thus, LS-CHM provides a unique pediatric and extramedullary AEL model, expanding the existing spectrum of AEL cell lines and offering valuable opportunities for biologic and therapeutic investigations.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by the lack of ER, PR, and HER2 expression. Its aggressive behavior, high degree of tumor heterogeneity, and immunosuppressive tumor microenvironment (TME) are associated with poor clinical outcomes, rapid disease progression, and limited therapeutic options. Although chimeric antigen receptor (CAR)-engineered T cell therapy has shown certain promise, its applicability in TNBC is hindered by antigen escape, TME-mediated suppression, and the logistical constraints of autologous cell production. In this study, we employed hematopoietic stem and progenitor cell (HSPC) gene engineering and a feeder-free HSPC differentiation culture to generate allogeneic IL-15-enhanced, mesothelin-specific CAR-engineered invariant natural killer T ( Allo15 MCAR-NKT) cells. These cells demonstrated robust and multifaceted antitumor activity against TNBC, mediated by CAR- and NK receptor-dependent cytotoxicity, as well as selective targeting of CD1d + TME immunosuppressive cells through their TCR. In both orthotopic and metastatic TNBC xenograft models, Allo15 MCAR-NKT cells demonstrated potent antitumor activity, associated with robust effector and cytotoxic phenotypes, low exhaustion, and a favorable safety profile without inducing graft-versus-host disease. Together, these results support Allo15 MCAR-NKT cells as a next-generation, off-the-shelf immunotherapy with strong therapeutic potential for TNBC, particularly in the context of metastasis, immune evasion, and treatment resistance. The online version contains supplementary material available at 10.1186/s13045-025-01736-9.

Erythroblast enucleation is a unique process during mammalian erythropoiesis, yet its regulatory mechanisms remain largely elusive. Here, we demonstrate the specific regulatory role of the oncogene PIM1, the most highly expressed protein kinase in orthochromatic erythroblasts, in enucleation. Unlike its well-established roles in cancer cell proliferation and survival, knockdown of PIM1 in human erythroid cells does not affect cell growth or apoptosis, but specifically inhibits erythroblast enucleation without altering differentiation. To elucidate the functional conservation of PIM1 in mammalian erythropoiesis, we generate Pim1fl/flEpoRCre mice in which Pim1 is deleted in erythroid cells. Consistent with human erythropoiesis, deletion of Pim1 in mice has no detectable effect on apoptosis or differentiation of erythroid cells, but specifically inhibits erythroblast enucleation. Phosphoproteomic analysis reveals that PIM1 deficiency causes a pronounced decrease in phosphorylation of GTPase-associated proteins involved in actin assembly and vesicle trafficking. Functionally, this perturbation results in an aberrant distribution of F-actin and endocytic vesicles within enucleating cells. These findings reveal the unexpected role of PIM1 in normal erythropoiesis and enhance our understanding of mammalian erythroblast enucleation. The oncogene PIM1 regulates erythroblast enucleation via GTPase-dependent cytoskeletal remodeling and vesicle trafficking, independent of its canonical roles in cell proliferation and apoptosis.