Regulatory Role of Megakaryocytes on Hematopoietic Stem Cells Quiescence by CXCL4/PF4 in Bone Marrow Niche

Platelet factor-4 (CXCL4/PF-4) is a member of CXC-chemokine family produced by megakaryocytic lineage and stored in platelet α-granules. Platelet stimulation by aggregating agents such as thrombin and ADP leads to CXCL4 secretion. CXCL4 plays several roles in coagulation, angiogenesis control, immune system modulation and spread of cancer. Megakaryocytes (Mks) are associated with the vascular niche in the bone marrow (BM) and are located in vicinity of BM sinusoids. Mk-derived CXCL4 is involved in several hematopoietic processes, including inhibition of megakaryopoiesis and maintenance of hematopoietic stem cell (HSC) quiescence. The major aim of this review article was to evaluate the role of CXCL4 in hematological malignancies, promotion of HSC quiescence as well as BM niche cells.