PLATELET- NEUTROPHIL COMPLEXES – DEFINITION, MECHANISMS AND IMPLICATIONS (REVIEW)

Neutrophils are innate immune cells that protect the host from infection by eliminating the invadingpathogens. In recent years, neutrophils and platelets have been shown to be active not only in inflammatoryprocesses but also in some pathological conditions, including the development of neoplastic diseases andthrombosis. The interaction between circulating platelets and neutrophils is characterised by the intensive exchangeof intracellular signals. Overexpression of some of these molecules has been reported, with increased leukocyte andplatelet activation as well as increased adhesion of blood cells to the vascular endothelium. Platelet-neutrophilinteractions are increased in thrombo-inflammatory diseases and are sensitive biomarkers for platelet activation andtargets for the development of new therapies. The crosstalk between platelets and innate immune cells promotesthrombosis, inflammation, and tissue damage.A key step in the formation of platelet-neutrophil complexes (PNCs) is the process of interaction between theadhesion molecule P-selectin (CD62P) on the platelet membrane and the PSGL-1 ligand on neutrophils. Theformation of PNCs modulates a wide range of pathological conditions, including both innate and acquired immunesystems. PNCs are involved in the pathogenesis of inflammatory diseases, malignancies and thrombotic processes.The formation of PNCs is associated with the initiation of a number of processes at the cellular and molecular levels.Malignant diseases are risk factors for the occurrence of arterial, venous and microthrombosis, which are most oftenassociated with hypercoagulable processes that form platelet aggregates. By modulating the immune system throughdirect and indirect interactions with leukocytes, platelets regulate several aspects of tumor-related pathology.Thisreview aims at summarizing the role of platelet-neutrophil interactions in the development and progression of cancerand puts its focus on cancer-related alterations of platelet and leukocyte functions and their impact on cancerpathology.The analysis and evaluation of the levels of the circulating platelet- neutrophil complexes in blood in neoplasticdiseases can be used as potential predictors of tumor progression, metastasis and the occurrence of thrombosis.