[Chronic myeloid leukemia stem cells: cross-talk with the niche]

The physiological hematopoietic niche located in bone marrow is a pluricellular structure whose components are now well identified. Within this microenvironment, hematopoietic stem cells are in direct contact with mesenchymal stromal cells, osteoblasts and sinusoidal endothelial cells. These close relationships drive specialized cellular functions (proliferation/quiescence, differentiation/self-renewal) ensuring an efficient hematopoiesis. Chronic myeloid leukemia (CML) is a major model of leukemic hematopoiesis. The BCR-ABL1 tyrosine kinase, constitutively activated in CML, plays a critical role in the pathogenesis of the disease. An intensive cross-talk between CML progenitors and the components of the hematopoietic niche has recently been demonstrated. Consequently, the occurrence of the so-called leukemic niche promotes both the proliferation of myeloid cells and the maintenance of quiescent leukemic stem cells. This bone marrow niche could also protect CML stem cells from tyrosine kinase inhibitors and probably contribute to their resistance towards targeted therapies.