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BackgroundCD24 plays a crucial role not only in promoting tumor progression and metastasis but also in modulating macrophage-mediated anti-tumor immunity. However,its impact on the immune landscape of the tumor microenvironment (TME) remains unexplored. Here,we investigated the role of CD24a,the murine CD24 gene,in tumor progression and TME immune dynamics in a murine triple-negative breast cancer (TNBC) model.MethodsClustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/Cas9 knockout technology was employed to generate CD24a knockout in the murine TNBC cell line 4T1. Flow cytometry was utilized to analyze the immune cell populations,including myeloid-derived suppressor cells (MDSCs),natural killer cells,T cells,and macrophages,within tumors,spleens,and bone marrow in the orthotopic mouse 4T1 breast cancer model. Immunofluorescence (IF) staining was used to detect the immune cells in tumor sections. High-speed confocal was used to perform three-dimensional (3D) mapping of immune cells in the 4T1 orthotopic tumors.ResultsKnocking out CD24a significantly reduced tumor growth kinetics and prolonged mouse survival in vivo. Flow cytometry and IF analysis of tumor samples revealed that CD24a loss significantly promoted the infiltration of M1 macrophages and cytotoxic CD8+ T cells into the TME while reducing the recruitment and expansion of granulocytic MDSCs (gMDSCs). In vitro coculture experiments showed that CD24a deficiency significantly enhanced macrophage‐mediated phagocytosis and CD8⁺ T cell-mediated cytotoxicity,effects that were partially reversed by re‐expression of CD24a. Moreover,in vivo depletion of macrophages and CD8+ T cells reverted the delayed tumor growth caused by CD24a knockout,underscoring their critical role in tumor growth suppression associated with CD24a knockout. 3D mapping of immune cells in the TME confirmed the anti-tumor immune landscape in the CD24a knockout 4T1 tumors. Furthermore,in vitro analysis showed that CD24a loss upregulated macrophage colony-stimulating factor expression while suppressed levels of CXCL1,CXCL5,and CXCL10,chemokines known to recruit gMDSCs,further providing a molecular basis for enhanced macrophage recruitment and diminished gMDSC accumulation.ConclusionsOur findings suggest that CD24a may regulate immune suppression within the TNBC TME. Targeting CD24a enhances macrophage- and CD8⁺ T cell-mediated anti-tumor immune responses and is associated with a shift in the TME toward a more immunogenic state,thereby suppressing tumor growth. These results may support CD24 as a promising immunotherapeutic target for TNBC.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12929-025-01165-3. View Publication

Peripheral nerve injury (PNI) remains a significant clinical challenge,often leading to long-term functional impairment. Despite advances in therapies,current repair strategies offer unsatisfactory clinical outcomes. Exosomes derived from induced pluripotent stem cells (iPSC-Exos) have emerged as a promising therapeutic approach in regenerative medicine. This study assesses the efficacy and safety of iPSC-Exos in a rat model of sciatic nerve crush injury. Briefly,iPSCs were generated from peripheral blood mononuclear cells (PBMCs) of healthy donors using Sendai virus vectors and validated for pluripotency. iPSC-Exos were characterized and injected at the injury site. Functional recovery was assessed through gait analysis,grip strength,and pain response. Histological and molecular analyses were used to examine axonal regeneration,myelination,Schwann cell (SC) activation,angiogenesis,and changes in gene expression. iPSC-Exos were efficiently internalized by SC,promoting their proliferation. No adverse effects were observed between groups on body weight,organ histology,or hematological parameters. iPSC-Exos injection significantly enhanced nerve regeneration,muscle preservation,and vascularization,with RNA sequencing revealing activation of PI3K-AKT and focal adhesion pathways. These findings support iPSC-Exos as a safe and effective non-cell-based therapy for PNIs,highlighting their potential for clinical applications in regenerative medicine. View Publication