PRF1 and neoplasm: Cytotoxic T cells and NK cells induce apoptosis, necrosis, and growth arrest of the cancerous cells by releasing IFN-γ, perforin, granzymes, etc. The apoptotic cancer cells and released components are phagocytosed/endocytosed by APCs, which process and present the antigenic peptides to lymphocytes in the lymphoid tissues for adaptive immune responses against the tumor.