Fig. 5: Intracellular SP decreases IFNβ secretion via degrading STING Protein.

A Heatmap showing the decreased expression of majority of ISGs compared SP to Control group (each group, n = 4) in HCT116 cells; SP treated 4 h. B qPCR testing the expression of CXCL10, ISG15, IFNB1, and IFIT1 in HCT116 cells. PAM3, LPS, and cGAMP treat HCT116 for 3 h. PAM3, Pam3CSK4, stimulates TLR2 ligand; LPS, stimulates TLR4 ligand; poly (I:C), stimulates MAVS; cGAMP, 2′3′-cGAMP, stimulates STING. Data are mean ± SEM from n = 4. C WB analysis in HCT116 pretreated with SP for 48 h, followed by a 3 h stimulation with cGAMP (left) and poly (I:C) (right); p-IRF3, IRF3 phosphorylate; p-TBK1, TBK1 phosphorylate; t-IRF3, total IRF3; t-TBK1, total TBK1. D ELISA analysis IFNβ secretion in HCT116 treated with cGAMP for 3 h after with or without infected SP for 48 h. Data are mean ± SEM from n = 3. E WB analysis STING protein in different cell lines treated with SP for 48 h in different MOI. F IF shows SP-GFP within HCT116 cells. ER, light blue; SP-GFP, green; Nucleus, DAPI, red. Scale bar = 15 μm, 5 μm. G ELISA analysis of IFNβ secretion in STING-KO HCT116. Data are mean ± SEM from n = 3. H Flow cytometry analysis of MHC-II⁺ macrophage populations following coculture with wild-type or STING-KO HCT116 cells. Data are mean ± SEM from n = 3. I Flow cytometry analysis of CD206⁺ macrophage populations following coculture with WT or STING-KO HCT116 cells. Data are mean ± SEM from n = 3. J Tumor volume (left) and tumor weight (right) in C57 mouse. STING-KO, knock out the gene of STING in MC38 cells. WT wild type; Data are mean ± SEM from n = 5. P values were determined by unpaired two-tailed t-tests unless otherwise specified (one-way ANOVA was used to multiple group comparisons). *p < 0.05, **p < 0.01, ***p < 0.001. Source data are provided as a Source data file.