Erythroid cells require specialized microenvironments called erythroblastic islands (EBIs), niches comprising a central macrophage surrounded by developing erythroid precursors, to complete their maturation. Understanding EBI composition and function has been limited by two-dimensional in vitro models and the unclear composition of EBIs in human hematopoietic tissues. Using spatial transcriptomic mapping in mouse and human hematopoietic tissues during development and under stress conditions, we show that EBI architecture is unexpectedly species-specific. In mice, C1q-expressing macrophages serve as a hallmark of EBI central macrophages and mediate clearance of ejected erythroid nuclei. In humans, however, EBIs are characterized by macrophage-independent erythroid clusters in fetal liver and bone marrow, whose integrity depends critically on the adhesion molecule ICAM4. These human erythroid clusters are disrupted in myeloid diseases but can be restored with therapy. These findings redefine conventional models of erythroid niche biology and establish a framework for understanding niche dynamics across species.

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.