Regulatory effect of chemokines in bone marrow niche.

Chemokines secreted from different cellular components of bone marrow (BM) play an important role in the formation of the BM niche system. The hematopoietic stem cell (HSC) pool located in specialized anatomical sites within the BM is subjected to a complex network of chemokines, such that the produced chemokines affect the fate of these cells. Expression of different chemokine receptors on leukemic stem cells (LSCs) uncovers the critical role of chemokines in the maintenance, survival and fate of these cells in the leukemic niche. As a pre-metastatic niche rich in a variety of chemokines, the BM niche is turned into a locus of tumor cell development and division. The chemokine receptors expressed on the surface of metastatic cells lead to their metastasis and homing to the BM niche. Knowledge of chemokines and their receptors leads to the production of various therapeutic antagonists at chemokine receptors expressed on leukemic and tumor cells, enabling interference with chemokine function as a therapeutic tool. New findings suggest that miRNAs, with their specific inhibitory function, affect the ability of producing and expressing chemokines and chemokine receptors. This review focuses on the emerging role of chemokines and their receptors in normal and pathologic conditions of the BM niche, and also discusses the new therapeutic methods with this background.