Normal and leukemic stem cell niche interactions

Purpose of reviewNormal hematopoietic stem cells (HSCs) and leukemic stem cells (LSCs) interact with the stem cell niche bone marrow in different ways. Understanding the potentially unique microenvironmental regulation of LSCs is key to understanding in-vivo leukemogenic mechanisms and developing novel antileukemic therapies.Recent findingsWhen leukemic cells are engrafted in the stem cell niche, the cellular nature of the niche - including mesenchymal stromal cells - is reprogramed. Altered mesenchymal cells selectively support leukemic cells and reinforce the pro-leukemic environment. As the niche plays an active role in leukemogenesis, its remodeling may significantly influence the leukemogenic pattern, and cause differences in clinical prognosis. Notably, niche cells could be stimulated to revert to a pronormal/antileukemic state, creating potential for niche-based antileukemic therapy.SummaryBone marrow microenvironments are under dynamic regulation for normal and leukemic cells, and there is bi-directional control of leukemic cells in the niche. Leukemic cells are both protected by stroma and able to reprogram stromal cells to transform the niche to a state, which reinforces leukemogenesis. Because of its dynamic nature, the niche could be converted to an environment with antileukemic properties, making it an attractive target for therapy.