Genetically engineered mice have been instrumental in validating the concept of tumour immunosurveillance as they provided direct evidence for the contribution of key immune components including IFNG, RAG2, STAT1, TCRδ, PRF1 and TNFSF10, to antitumor responses mediated by both innate and adaptive effector cells2, 3. Here, PRF1 is linked to neoplasm.