CXCL12 and acute lymphoblastic leukemia: Our NBM-ALL competence data suggest the existence of two distinct niches of MSC at ALL diagnosis: one constituted by CXCL12hiSCFhi MSC, which better support normal hematopoiesis and might be endowed with repressor functions for leukemia, and a second niche composed by remodeled MSC which CXCL12 and SCF production is abated and favors growing of malignant cells (Figure 7).