Interleukin-27 remodels the bone marrow niche to suppress B-cell development and leukaemia progression in mouse models

BACKGROUND: Interleukin-27 (IL-27) is an immunoregulatory cytokine, but its role in B-cell haematopoiesis and B-cell acute lymphoblastic leukaemia (B-ALL) within the bone marrow (BM) niche remains unclear. METHODS: IL-27 was delivered in vivo using adeno-associated virus. B-cell reconstitution, mixed BM chimeras, and an N-myc-driven B-ALL model were analysed by flow cytometry, transcriptional profiling, and survival studies. Group comparisons were assessed using Student's t-test, and survival was evaluated by Kaplan-Meier analysis with log-rank tests. FINDINGS: Sustained IL-27 expression selectively impaired B-cell reconstitution while preserving overall haematopoietic recovery, with marked reductions in CLPs and early B-cell subsets. IL-27 directly inhibited early B-lineage differentiation and concurrently remodelled the BM microenvironment by downregulating VCAM-1, ICAM-2, CXCL12, and IGF-1. These niche alterations were associated with reduced BM-resident B-ALL burden, enhanced chemotherapy efficacy, and improved survival in B-ALL-bearing mice. IL-27 showed no direct cytotoxicity toward B-ALL cells, supporting an indirect, niche-mediated mechanism. INTERPRETATION: IL-27 constrains B-cell haematopoiesis and B-ALL progression through coordinated progenitor inhibition and BM niche remodelling, revealing a cytokine-driven strategy with the potential to enhance leukaemia therapy. FUNDING: This work was supported by the National Key R&D Program of China (Grant No. 2021YFA1100800 to A.-B.L.) and the National Natural Science Foundation of China (Grant No. 82100180).