Exendin-4 Exhibits Enhanced Anti-tumor Effects in Diabetic Mice

Type 2 diabetes (T2D) is associated with increased risk of cancers. In this connection, we previously demonstrated the promoting effect of diabetes on HPV-associated carcinogenesis using a xenograft model in db/db diabetic mice. The underlying mechanism of this observation might be partly contributed by dysregulated immune response in diabetes. In this study, we hypothesized that the impaired anti-tumor immune response in diabetic status could be modulated by exendin-4, a glucagon-like protein receptor agonist which exhibits anti-diabetic effects. We inoculated 10-week old db/db mice with 2 × 10⁷ CUP-1 cells (Human Papilloma Virus (HPV)-16 E7 transfected continuous cell line) subcutaneously underneath the scruff, and treated mice with high (30 nmol/kg) or low (10 nmol/kg) dose of exendin-4 for 13 days. 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. Collectively, these findings suggested an anti-tumor effect of exendin-4 in diabetic conditions, which might be resulted from direct immunomodulation.