PRF1 and cancer: Cytotoxic lymphocytes, cytotoxic T cells, and natural killer cells are the main players in this process, since exocytosis of their granules (perforin and granzymes) and death ligands initiate the most potent pathways used to kill cancer cells, overcoming antiapoptotic mutations, including p53 deletion/mutation, overexpression or downregulation of members of the Bcl-2 family, and caspase inhibition [32].