Figure 7. The identified nucleotide compounds could activate STING and enhance anti-tumor immunity. (A) ADP assay for cells treated with or without metformin (1 mM). (B) Cell viability of cells treated with metformin (1 mM), activated T cells (1:1 ratio to cancer cells), or activated T cells combined with metformin or nucleotide compounds (1 mM). (C) Ki67 incorporation assay in H460 cells and Axin1^-/- H460 cells treated as indicated. Activated T cells (1:1 ratio to cancer cells), metformin or nucleotide compounds were added to the culture medium for 48 h. Cells were then counterstained with DAPI. scale bars: 100 μm. (D) ELISA analysis of IFN-γ in supernatants from inactivated or activated T cell cultures treated with nucleotide compounds (0, 0.5, or 1 mM, respectively) for 48 h. (E) Western blot analysis of indicated proteins in H460 and Axin1^-/- H460 cells with metformin or nucleotide compounds treatment. (F) ELISA analysis of IFN-β in H460 and Axin1^-/- H460 cells treated with metformin or nucleotide compounds. (G) Representative immunofluorescent staining of STING in H460 and Axin1^-/- H460 cells upon metformin or nucleotide compounds administration. Scale bars: 200 μm. Data are presented as mean ± SD of triplicate determinations (for A–D and F). The significant difference was shown as *p < 0.05; **p < 0.01; ***p < 0.001. Metf: metformin; Nucle: nucleotide compounds.