FIGURE 4.

AXIN-1 was required for metformin to stabilize STING. (A), Cell lysates from AXIN-1 knockout clones of H460 cells by CRISPR/CAS9 (KO-6 and KO-7) were subjected to western blot. (B), AXIN-1 ^+/+ cells and AXIN-1 ^−/− cells co-cultured with activated T cells (cancer cells to T cells ratio, 1:1) for 48 h with or without metformin were subjected to crystal violet staining. (C), Cell viability CCK-8 assay for AXIN-1 ^+/+ cells and AXIN-1 ^−/− cells treated as indicated. Data are shown as mean ± SEM. *p < 0.01. (D), Ki67 incorporation assay on AXIN-1 ^+/+ cells and AXIN-1 ^−/− cells treated as indicated. Cells were counterstained with DAPI. (E), AXIN-1 ^+/+ cells and AXIN-1 ^−/− cells were treated with 10 μM CHX at indicated intervals in the presence of metformin or not. The intensity of STING protein was quantified using ImageJ software.