Setdb1 deficiency resulted in the expansion of tumor-infiltrating cytotoxic CD8+ T cells and p15E-tetramer+ T cells as along with the upregulated genes related with cytotoxicity among p15E-specific TCR, which is known to initiate MuLV-derived MHC-I peptide for stimulating antineoplastic T-cell responses. This evidence concerns the gene CD8A and neoplasm.