PRF1 and neoplasm: Functional analysis has shown that type 1 cytotoxic T cells (Tc1) represent the main component of the terminal end route of anticancer immunity by producing high levels of cytolytic cytokines such as perforin, INF‐y, and granzyme B, thereby initiating direct tumor cell killing [8, 10], while other cytotoxic T‐cell subsets such as type 2 (Tc2) [8, 11] or regulatory cytotoxic T cells (Tcreg) [12] contribute less effectively to tumor cell destruction.