Combination of STING agonist and CXCR3 antagonist disrupts immune tolerance to overcome anti-PD-L1 resistance in lung adenocarcinoma under oxidative stress

We investigated the role of the STING1-CXCR3 axis using database data and verified it in a mouse model bearing Lewis lung carcinoma (LLC) cells exposed to hydrogen peroxide (H2O2). Mice were treated with STING agonist liposomes (STING-Lip), anti-programmed death-ligand 1 (PD-L1), or STING-Lip + anti-PD-L1. The database data revealed that immune response pathways were enriched in patients with lung adenocarcinoma with upregulated STING1 signaling. Upregulated STING1 signaling was associated with a high abundance of immunoregulatory and effector molecules, cytokines, activated CD8+ T cells, and M1 macrophages in patients with lung adenocarcinoma. In this study, H2O2-treated LLC cells promoted an immunosuppressive microenvironment and enhanced tumor growth in mice. STING-Lip inhibited distant, untreated, and H2O2-induced LLC growth by activating systemic immunity. STING-Lip + anti-PD-L1 failed to slow distant and untreated LLC growth, whereas STING-Lip + anti-PD-L1 + CXCR3 antagonist inhibited distant tumor growth in mice. The combination of STING1 activation and CXCR3 inhibition may be a novel immunotherapeutic strategy to overcome immune checkpoint inhibitor resistance in lung adenocarcinoma by activating systemic immunity in the tumor microenvironment under oxidative stress.