Normal Versus Leukemic Bone Marrow Niche. Figure depicting a normal bone marrow niche with functional hematopoiesis, versus a re-programmed “leukemic” niche where hematopoietic stem cells (HSCs) are lost and HSC maintenance is impaired, favoring leukemic proliferation. Impaired maintenance of hematopoiesis occurs through leukemia-driven expansion of an altered early osteoblastic lineage precursor cell population (OBC) with down-regulated HSC retention signaling factors such as stem cell factor (SCF), chemokine ligand 12 (CXCL-12), and angiopoietin (Angpt1). The altered OBC expansion follows direct leukemic influence on the parent, multipotent stromal cell (MSC) population, rather than on the OBCs themselves, possibly through alterations in chemokine ligand-3 (CCL-3), thrombopoietin (TPO), direct cell contact, or other means.Figure created by Dr. Shelton Viola.