Figure 1. Efficient 5‐FU‐induced reduction of tumor burden in immunocompetent host is dependent on cancer‐cell‐intrinsic STING.

• A
  Schematic illustration of the syngeneic tumor model in which MC38 colon cancer cells were injected subcutaneously. 5‐FU (25 mg/kg per dose) was administered intraperitoneally from day 6 after cancer cell injection, with one dose every 2 days. Tumor and spleen were harvested at 2 weeks.
• B
  Tumors formed with WT MC38 cells were treated with PBS or 5‐FU. Tumor volumes were quantified at the indicated days. N = 5.
• C
  STING‐KO or sgRNA control (Ctrl) MC38 cells were treated in vitro with the indicated concentrations of 5‐FU. Cell viability were determined using the CellTiter‐Glo assay after 2 days, with normalized luminescence levels shown. N = 3.
• D–F
  Mice were injected with Ctrl or STING‐KO MC38 cells, and treated with PBS or 5‐FU. (D) Pictures of tumors and spleens from a representative experiment. Image panels were cropped from the same picture. (E) Tumor volumes were quantified at the indicated days after cancer cell injection. N = 4 to N = 5 as shown in (D). (F) Tumor and spleen weights at the endpoint for (E), with each dot representing a mouse.
• G–I
  WT MC38 cells were injected into STING^+/+ or STING^−/− mice and treated with 5‐FU or PBS following the schematics in (A). (G) Pictures of tumors and spleens from a representative experiment. Image panels were cropped from the same picture. (H) Tumor volumes were quantified at the indicated days after cancer cell injection. N = 5. (I) Tumor and spleen weights at the endpoint for (H), with each dot representing a mouse.

Data information: For all panels, error bars stand for SD, and center values represent mean. Two‐tailed unpaired Student’s t‐test was used. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns: not significant. Data in (B, D–F) are representative of at least four independent experiments. Data in (C, G–I) are representative of two experiments.