Platelets: Traditional and nontraditional roles in hemostasis, inflammation and cancer

Abstract

The principal and the most known function of platelets still remains stopping hemorrhage following vascular injury. However, platelets are involved in diverse processes such as triggering inflammation, participating in the immune response, besides tumor progression, angiogenesis, and metastasis. In this sense, it is becoming increasingly clear that platelets display inflammatory functions and can influence both innate and adaptive immune responses, such as autoimmune and alloimmune platelet disorders, and transfusion-related acute lung injury (TRALI). Despite much speculation recent observations have established new paradigms relevant to influence of platelets on molecular biology. Primary human platelets contain essential spliceosome factors including small nuclear RNAs, splicing proteins, and endogenous pre-mRNAs. Other point is, like all lineages of blood cells, the steady state number of mature platelets is the result of a balance between their production and destruction. Thus, it is proposed a programmed anuclear cell death delimits platelet life span is subject of speculation since the 1960s and has remained elusive. The general notion that functional platelets are important for successful hematogenous tumor metastasis dates more than 4 decades and has been corroborated in numerous experimental settings. The dynamic crosstalk between tumors and their microenvironment is increasingly recognized as a key regulator of malignant progression. These contributions of platelets to tumor cell survival and spread suggest platelets as a new avenue for research. Here, we discuss the mechanisms by which platelets contribute to immunity, inflammation, and cancer, since these small cells are more versatile than we once thought.