Abstract 6636: Metformin suppresses tumor immune evasion through downregulation of PD-L1 expression in cancer cells and PD-1 expression in NK cells and T cells

Abstract

Abstract Up-regulation of programmed cell death 1 (PD-1) receptor on T cells and its ligand (PD-L1) on cancer cells is reported in various tumor microenvironment, and the interaction between PD-L1 and PD-1 inhibits the cytotoxic activity of NK cells and T cells, allowing cancer cells to evade immune destruction. Extensive studies suggested that metformin, the most widely used first-line drug for treatment of type 2 diabetes, had a potential efficacy of enhancing anti-tumor immune response. However, the detail mechanisms underlying the efficacy are unknown. Here, we showed that metformin decreases AKT-mediated β-catenin S552 phosphorylation and β-catenin transactivation in an AMPK activation-dependent manner, resulting in reduced CD274 transcription in cancer cells. In the cocultures of cancer cells with NK cells or T cells, cancer cells induced PD-1 protein stability and expression in the NK cells and T cells, these PD-1 upregulation was also observed in infiltrated NK cells and T cells in vivo mouse tumors. Metformin reduced the half-life and expression of PD-1 in an AMPK activation-dependent manner in vitro and in vivo. These inhibitory roles of metformin in PD-L1 expression in cancer cells and in cancer cell-induced PD-1 expression in NK cells and T cells led to ameliorated the cancer cell-reduced cytotoxic activity of NK cells and T cells and inhibited tumor growth in vivo models. These findings suggest that metformin may act as both PD-L1 and PD-1 blockades within tumor microenvironment, providing a mechanistic insight for the efficacy of metformin to improve immunotherapy in human cancer. Citation Format: Su Hwan Park, Jong-Ho Lee. Metformin suppresses tumor immune evasion through downregulation of PD-L1 expression in cancer cells and PD-1 expression in NK cells and T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6636.