Fig 2: S100A8/A9 produced by MDSC induce 18F-FDG-uptake.a The SUV max of on the site of S100A8/A9 heterodimer injection by 18F-FDG-PET/CT. Mice were subcutaneously injected with indicated concentrations of S100A8/A9 heterodimer. 18F-FDG-PET/CT was performed 24 h after the injection, and the SUV max of the injection site was analyzed (PBS, n = 3; others, n = 2). b Representative immunoreactivities of resected paraaortic lymph nodes for S100A8 and S100A9 (ME180-Control-derived tumor- or ME180-GCSF-derived tumor-bearing rats). Scale bars, 50 µm. c Representative image of S100a8 and S100a9 mRNA expression in MDSC of ME180-GCSF-derived tumor-bearing mice as evaluated by RT-PCR. bp, base pairs. Source data are provided as a Source Data file.

Fig 3: Mechanism of S100A9 Effect on Macrophages(A) Left: proliferation of OT-1 splenocytes in the presence of specific peptides in the presence of CD11b+Gr-1+ myeloid cells from BM of WT or S100A9 Tg tumor-free mice. Right: IFN-? ELISpot. Experiments were performed in triplicate and repeated twice. Mean and SD are shown.(B) T cell proliferation of OT-1 splenocytes in the presence of specific peptides and Mon-derived macrophages from WT or S100A9 Tg tumor-free mice. Dotted line indicates cell proliferation in the absence of macrophages. Experiments were performed in triplicate. Results of individual mice (n = 3–5) and mean and SD are shown. p values were calculated in two-sided Student’s t test.(C) Indicated gene expression in WT or S100A9 Tg Mon-derived macrophages. Expression was normalized togadph. Results of individual mice (n = 3) and mean and SD are shown. p values were calculated in two-sided Student’s t test.(D) Relative expression of cebpb in WT or S100A9 Tg TAMs isolated from LLC TB mice.(E) Expression of C/EBPß-targeted genes in WT, S100A9Tg, and S100AKO TAMs isolated from LLC TB mice. Expression was normalized to gadph. Results of individual mice (n = 3–5) and mean and SD are shown. p values were calculated in two-sided Student’s t test.(F) Expression of C/EBP-ß-targeted genes in BMDMs or TR macrophages isolated from lung tissue of EL4 TB mice. Expression was normalized to actb. Results of individual mice (n = 4) and mean and SD are shown. p values were calculated in two-sided Student’s t test.(G) Expression of Arg-1 in control siRNA or C/EBP-ß siRNA S100A9 Tg Mon-derived macrophages. n = 4.(H) Proliferation of OT-1 splenocytes in response to specific peptides in the presence of Mon-derived macrophages treated with control siRNA or C/EBP-ß siRNA. n = 5. Dotted line indicates cell proliferation in the absence of macrophages. Mean and SD are shown. p values were calculated in two-sided Student’s t test.

Fig 4: RNA-seq after treatment with anti-S100a9 Ab in colitis-associated cancer (CAC) mouse model. (A) Hierarchical clustering of 585 transcripts that were upregulated (=2-fold change) in azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced CAC mice and were downregulated significantly in anti-S100a9 Ab treatment CAC mouse model, with three repeats. (B) KEGG pathway was used to analyze the pathways related to the 585 genes. The top 20 positively enriched pathways were shown in bubble chart. The x-axis is enrichment score, and the y-axis is enriched pathways. The larger the bubble is, the greater the number of different genes contained in pathway. The bubble color is changed from red to blue to green and to yellow, indicating the more larger p-value of the pathway enrichment. (C) The 585 genes were involved in signaling pathways, such as Wnt signaling pathway, cytokine–cytokine receptor, PI3K–AKT signaling pathway, focal adhesion, ECM–receptor interaction, and TGF-ß signaling pathway, as shown in heatmaps. Each row represents a single gene, and each column represents one tissue sample. Red indicates high relative expression, and green indicates low relative expression.

Fig 5: Therapeutic effects of anti-S100a9 Ab treatment on dextran sulfate sodium (DSS)-induced acute colitis in mice. (A) ICR mice received either 4% DSS-containing or distilled water alone (Control) for 6 days. DSS-treated mice were injected intraperitoneally with either negative control IgG or anti-S100a9 Ab, or anti-tumor necrosis factor alpha (TNFa) Ab at a dose of 1.5 and 5 mg/kg, respectively, on days 2 and 4; n = 15 per group. (B) Change in body weight over time was expressed as the percentage of the initial body weight. (C) The disease activity index (DAI) was measured every day; DAI = weight loss score + stool characters score + hematochezia score. (D) The colon length was measured at day 6. Student’s t-test, error bars represent SD. *p < 0.05, **p < 0.01, and ***p < 0.001, ns, non-significant.