Microparticles in tumor progression.

Microparticles (MP) are shed from the surface of activated or apoptotic blood cells and their levels in plasma reflect a balance between cell stimulation, proliferation, and death. MP production occurs through vesiculation of cell membranes, and involves cytoskeletal changes and a shift in the normal phospholipid asymmetry. The expression on the majority of MP of the anionic phosphatidylserine (PS) is responsible for the capacity of MP to support blood coagulation activation. In some cases, PS expression is also associated, in the same MP, with the presence of active Tissue Factor, the main activator of blood coagulation. Elevation in plasma levels of MP have been described in numerous clinical conditions, most of which also associated with an increased thrombotic risk. Particularly, MP have been found to be increased in both solid and hematological malignancies, including myeloproliferative neoplasms. A role of MP in tumor progression has been suggested by both in vitro and in vivo studies. Evidence exists that MP of platelet origin are the main players in this process, being rich in pro-angiogenic factors. The utility of measuring MP as a diagnostic and prognostic marker is currently a subject of intense investigation. The possibility to inhibit MP production by pharmacological interventions represents a future challenge.