Finally, T cell activation influences migration towards the vasculature and the infiltrating tumour microenvironment; the T cell receptor (TCR) interacts with MHC I leading to the recognition of specific cognate antigens and their binding to cancer cells; and Fas–Fas ligands interact with each other releasing specific substances, including enzymes or perforin particles, which are cytotoxic leading to the killing of the targeted cancer cells [4, 5]. Here, FAS is linked to cancer.