[cGAS-STING agonist cGAMP enhances natural killer cell-mediated cytotoxicity against gastric cancer cells].

[OBJECTIVES] To explore the molecular mechanism by which cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) agonists enhance cytotoxicity of natural killer (NK) cells against gastric cancer cells.

[METHODS] NK-92 cells were cultured in X-VIVO15 medium to a density of 1×10⁶/mL and treated with 5, 1, or 0.2 μmol/L cGAMP for 24 h before co-culture with gastric cancer MGC-803 and MKN-45 cells in RPMI 1640 medium. The expression of IFN-γ in co-cultured NK-92 cells and tumor cells was detected by qPCR and ELISA. The treated NK-92 cells were then co-cultured with the tumor cells labeled with CellTracker™ CM-DiI at different ratios (1:1, 2:1, and 4:1), and tumor cell viability and cytotoxicity of NK-92 cells were determined using a dead cell staining kit and flow cytometry-based cytotoxicity assay.

[RESULTS] The cGAS-STING agonist cGAMP dose-dependently enhanced mRNA expression and secretion of the pro-inflammatory cytokines (such as IFN-γ and TNF-α) in NK-92 cells, and NK-92 cells treated with 5 μmol/L cGAMP showed approximately 3-fold increase of IFN-γ and TNF-α levels. cGAMP treatment also upregulated the expression of activating receptors (such as NKp36 and NKp44) on the cell surface and activated the STING-TBK1-IRF3 signaling pathway in NK-92 cells. NK-92 cells pretreated with cGAMP showed increased cytotoxicity against MGC-803 and MKN-45 cells, which could be reversed by treatment with H-151 (a STING inhibitor). In tumor-bearing nude mice, combined treatment with cGAMP and NK cells reduced the mass of xenografts by nearly 40% and significantly slowed tumor growth.

[CONCLUSIONS] Activating the cGAS-STING pathway can enhance IFN-γ secretion of NK cells to improve their cytotoxicity against gastric cancer cells, suggesting a therapeutic strategy for gastric cancer using NK cells combined with STING agonists.