In a pancreatic ductal adenocarcinoma (PDAC) study, despite the finding that tumor-specific CD8+ T cells were observed in the tumor regions of PDAC mouse models, the mice did not respond to two immune checkpoint blockers (A-CTLA-4 and A-PD-L1) that promote the activity of T cells with tumor-inhibiting potential. This evidence concerns the gene CD8A and neoplasm.