Figure 1.

STING agonist cGAMP activated NK cells directly and promotes the killing capability of NK cells. (a) The time-dependent phosphorylation of IRF3 in NK-92 cells is shown after 4 μg/mL cGAMP stimulation. The data shown are representative of three independent experiments. (b) Up-regulation of IFN-β in NK-92 cells was detected by RT-PCR after stimulation with 1, 2, and 4 μg/mL cGAMP, respectively, for 24 h. (c) The levels of IFN-β in the supernatant of NK-92 cells measured by ELISA after stimulation with 4 μg/mL cGAMP. (d) Flow cytometry analysis of CD69, CD107a, perforin, granzyme B, IFN-γ, and TNF-α in NK-92 cells following stimulation with 4 μg/mL cGAMP for 24 h. The isotype group was used as a negative control to exclude background differences; PMA and ionomycin were used as positive controls. MFI, the mean fluorescence intensity. (e) The expression of activating receptors on the surface of NK-92 cells detected by RT-PCR after stimulation with 4 μg/mL cGAMP for 24 h and normalized to GAPDH. (f) The expression of inhibitory receptors on the surface of NK-92 cells detected by RT-PCR after stimulation with 4 μg/mL cGAMP for 24 h and normalized to GAPDH. (g, h) NK-92 cells were stimulated with 4 μg/mL cGAMP for 20 h, and co-cultured with AsPC-1 cells (g) and Capan-2 cells (h) for 4 h, then the cytolytic activity of NK cells was detected using the LDH assay. Data are shown as means ± SEM, and statistical significance was determined as ns: not significant, ***p < .001, **p < .01 and *p < .05.