These cells counteract cancer progression in mouse models by killing cancer cells with granzymes and perforin as well as upregulating MHC-I expression on cancer cells to increase CD8+ T-cell recognition (Dadi et al, 2016; Gao et al, 2003; Lanca et al, 2013; Riond et al, 2009). The gene discussed is PRF1; the disease is cancer.