cGAS-STING pathway reprograms macrophage polarization and is highly expressed in responding tumors after neoadjuvant immunotherapy in head and neck carcinoma

Given the critical role of the cGAS-STING pathway in antitumor immunity, this study investigates the functional role of STING in head and neck squamous cell carcinoma (HNSCC) to evaluate the therapeutic potential of STING agonists. Analysis of the TCGA-HNSC dataset reveals that elevated expression of the STING-encoding gene <i>TMEM173</i> is significantly correlated with increased M1 macrophage infiltration and enrichment of macrophage polarization-related signaling pathways. <i>In vitro</i> experiments in which RAW 264.7 cells are co-cultured with tumor cell-conditioned medium demonstrate that the STING agonist MSA-2 effectively reprograms tumor-induced M2-polarized macrophages toward the M1 phenotype. This MSA-2-induced M1 polarization is accompanied by increased expressions of IFN-α, IFN-β, IFN-γ, TNF-α, and IL-6, while the STING inhibitor H-151 reverses these effects. Flow cytometry further reveals that MSA-2 treatment reduces PD-1 and increases MHC II expression on macrophages. Immunohistochemical analysis of clinical samples confirms that high STING expression is correlated with increased numbers of CD68⁺ and CD80⁺ (M1-like) macrophages. In support of translational relevance, analysis of single-cell RNA-seq data from HNSCC patients receiving neoadjuvant immunotherapy indicates that TMEM173 is expressed primarily in T cells and macrophages and that the cGAS-STING pathway score is significantly higher in patients who respond to treatment. Collectively, these findings provide systematic clinical and experimental evidence supporting the potential of STING agonists, such as MSA-2, to enhance antitumor immunity in HNSCC, particularly when combined with immunotherapy.