TGF-β signaling and the interaction between platelets and T-cells in tumor microenvironment: Foes or friends?

Abstract T-cells, as the main immune cells in fighting against cancer cells, are usually overwhelmed by many factors. Tumor microenvironment (TME) changes are one of the factors that can limit T-cells functions. On the other hand, platelets which are known as the main source of transforming growth factor-β (TGF-β) in TME, are seemingly insignificant immune cells that can affect T-cell functions. There is a hypothesis that platelets might prevent tumor growth by stimulating cellular immunity, especially T-cells in pre-cancer status while they can inhibit T-cells and stimulate tumor growth in the advanced stage of cancer. Therefore, platelets could act as a double-edged sword in the activation of T-cells under pre-cancer and advanced stages of cancer conditions. In this review, the interaction between platelets and T cells in pre-cancer and advanced stages of cancer and the role of TGF-β signaling in different stages of cancer will be discussed.