Mitochondria targeted metabolic inhibitors promote lymphocyte infiltration into murine pancreatic tumors

Abstract

Abstract Pancreatic ductal adenocarcinoma is a malignant carcinoma with a 5-year survival rate of 11% characterized with poor prognosis, rising incidence, and resistance to chemo- and immune-therapies. Cancer cell evasion and suppression of anti-tumor immune responses in pancreas cancer are regulated in part by metabolic reprogramming within cancer and tumor accessory cells. We sought to determine if targeted inhibition of mitochondrial oxidative phosphorylation by mito-metformin (MMe) and newly developed variant pCF3-MMe influence the tumor immune microenvironment. Our results showed that MMe strongly inhibited tumor growth in murine models of pancreas cancer. Flow cytometry revealed a significant increase in total CD45+ leukocytes, with elevated cytolytic granzyme B+ and CD44+ CD8+ T cells. Immunodepleting CD8+ T cells, reversed the anti-tumor effects of MMe. Immunofluorescence microscopy and immunoblot analysis indicated that MMe stimulated oligomerization of mitochondrial antiviral-signaling protein (MAVS) and phosphorylation of IRF3 and IRF7. Further, levels of the IRF3/7 target chemokines CXCL9, CXCL10, and CXCL11 were increased in MMe-treated tumor cells, consistent with a role in CD8+ T cell infiltration. These data indicate OXPHOS inhibition stimulated virus-independent MAVS oligomerization, activation of downstream proinflammatory signaling, and reignition of the suppressed pancreatic tumor immune microenvironment. Funding Provided by NIH (2211376.1-5 R01 CA226279-01.04) and Center for Immunology MCW