Platelets, circulating tumor cells, and the circulome.

Platelets are cytoplasmic fragments generated by megakaryocytes in the bone marrow and do not possess a nucleus. They contribute to the "Circulome" consisting of all circulating cells, factors and macromolecules such as cfDNA. Their primary function is to recognize vascular lesions and initiate thrombus formation that ceases bleeding. This distinctive characteristic of platelets also contributes to cancer and its progression. The ability of platelets to recognize and interact with other cells and neighboring platelets enables them to interact with tumor cells in the circulation. Receptor recognition and factor mediated crosstalk between tumor cells and platelets stimulate platelet activation, release of factors, and aggregation that promotes tumor cell survival and cancer progression. This review describes platelet: (i) contributions to the "Circulome" (ii) their importance as diagnostic tools in predicting cancer risk and (iii) therapies targeting platelet activation in inhibiting tumor progression and metastasis.