Compared with control groups, exendin-4 suppressed subcutaneous tumor growth in a dose-dependent manner, accompanied by increased interferon (IFN)-γ secreting CD8+ cytotoxic T lymphocyte (CTL)/Foxp3+ regulatory T cell (Treg) ratio as well as Th1 proinflammatory cytokines IFN-γ and IL-2. This evidence concerns the gene CD8A and neoplasm.