Decreased cytokine production and/or antigen presentation in gene-deficient mice, including Perforin−/− (lack perforin) [49], Ifng−/− (lack IFN-γ) [50], Perforin−/−Ifng−/− (lack perforin and IFN-γ) [50], Perforin−/−B2m−/− (lack perforin and MHC class I expression) [51], and Lmp2−/− (defective MHC class I antigen presentation) [52], facilitates tumor growth. Here, PRF1 is linked to neoplasm.