Extended Data Fig. 3. P. anaerobius induced anti-PD1 immunotherapy resistance by modulating MDSCs.

a. Schematic diagram for the MC38 allograft model (Right). Representative images of tumours after harvesting (left). b. Percentage of G-MDSCs (left), PD1⁺CD8⁺T cells (right) in MC38 allografts. 5 mice were used in each group. c. Schematic diagram of AOM/DSS induced CRC mouse model. Representative images of mouse colonoscopy at day 100 (left), images of colon and tumour numbers (middle), quantification of tumour burden (right) in each group. PBS (n = 11), PBS+ a-PD1 (n = 11), PA (n = 11), PA+ a-PD1 (n = 12). d. Representative tumour flow plots and percentage of MDSCs in tumours from AOM/DSS mice model. PBS (n = 9), PBS+ a-PD1 (n = 10), PA (n = 10), PA+ a-PD1 (n = 11). e. Immunofluorescence quantification of CD11b⁺Gr-1⁺ cells in tumour from AOM/DSS mice model. Scale bar: 25 μm. f. Representative tumour flow plots and percentage of IFNγ⁺CD8⁺T cells in tumours from AOM/DSS mice model. PBS (n = 10), PBS+ a-PD1 (n = 11), PA (n = 10), PA+ a-PD1 (n = 11). g. Percentage of PD1⁺CD8⁺T cells in AOM/DSS mice model. PBS (n = 9), PBS+ a-PD1 (n = 9), PA (n = 9), PA+ a-PD1 (n = 10). h. Schematic diagram of MDSC depletion using anti-Ly6G antibody in MC38 allograft model (left), and representative image of tumours after at sacrifice (right). 5×10⁵ MC38 cells were subcutaneously injected into C57BL/6 J mice (n = 5). After 6 days, mice were injected with P. anaerobius intratumorally and followed by PD1 mAb treatment. 250ug anti-Ly6G was intraperitoneally injected every 48 hrs to deplete MDSCs in mice. i. Percentage of MDSCs in blood from different groups of mice were determined by flow cytometry. j. MFI of IFNγ⁺CD8⁺T cells in tumour were determined by flow cytometry. h-j 5 mice were used in each group. Data are presented as mean ± SEM. P values were calculated by one-way ANOVA followed by Tukey’s post-hoc test(b-g, i-j).

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