Longitudinal localization of leukaemic stem cells between the metaphysis and central marrow governs their behaviour

Leukaemic stem cells (LSCs) reside in protective bone marrow (BM) niches that promote therapeutic resistance and relapse. Here we characterized longitudinal BM niches supporting LSC survival, distinguishing the metaphysis from the central marrow. Quiescent LSCs preferentially localized to the metaphysis and exhibited reduced stemness and aggressiveness upon mobilization to the central marrow. Targeting DPP4 in acute myeloid leukaemia (AML) cells altered CXCL12 gradients at three spatial scales. Systemically, reversal of the BM-peripheral blood CXCL12 gradient confined AML cells within the BM. At the BM level, disruption of the metaphysis-central marrow gradient displaced LSCs from their protective niche. At the microscale, loss of the CXCL12 gradient between N-cadherin⁺ stromal cells and the surrounding matrix impaired LSC recruitment. These effects arise from the CXCL12-DPP4-GPC3 axis, in which DPP4 truncates and inactivates CXCL12, whereas stromal GPC3 restrains DPP4 activity. Modulating this axis disrupts niche protection and enhances therapeutic vulnerability in AML.