CGAS-STING signaling encourages immune cell overcoming of fibroblast barricades in pancreatic cancer

Abstract

Immune checkpoint blockade (ICB) treatment improves the prognosis of several types of solid tumors, however, responsiveness to ICB therapy remains low in pancreatic ductal adenocarcinoma (PDACs), which has a rich tumor microenvironment (TME). The TME is composed of various stromal cells, including cancer-associated fibroblasts (CAFs), which contribute to the establishment of an immunosuppressive microenvironment. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is an innate immune pathway that results in the upregulation of immune cell recruiting-cytokines and anti-tumor efficacy. In this study, we aimed to investigate the impact of cGAS-STING expression and the presence of CAFs upon immune cell infiltration in PDACs. cGAS and STING co-expressing PDAC cases showed favorable survival, with many cytotoxic CD8 + T cell infiltrations from the stromal component adjacent to the cancer cells toward cancer cells, but not in cGAS-STING signaling defected PDAC cases. The signatures of tumor-restrain CAFs were expressed in tumors with cGAS-STING signaling. Finally, transwell co-culture experiments demonstrated that immune cell infiltration was impeded by the presence of CAFs, but not by activation of cGAS-STING signaling. In conclusion, pro-infiltration signals, such as cGAS-STING, and characterization of CAFs are crucial in defeating CAF barricades and encouraging immune cell infiltration in PDACs.