Fig 2: DPEP1-KO mice present with immune-related features of microsatellite instability.Representative immunofluorescence images for WT Ads and DPEP1-KO ACAs stained for (A) MPO, (B) H3-cit, and (C) CD8 merged with DAPI staining. Scale bars: 100 μm. (D and E) Representative PD-L1 IHC staining for WT Ads and DPEP1-KO ACAs. Scale bars: 150 μm (D) and 50 μm (E and insets in D). Representative images are a result of staining tumors from 2 cohorts described in the Methods, where experiments were done in triplicate from WT (n = 12) and DPEP1-KO (n = 10) tumors.

Fig 3: DPEP1-KO mice display features of microsatellite instability in epithelial cells.Representative immunofluorescence images for WT Ads and DPEP1-KO ACAs stained for (A) MSH6 and β-catenin or (B) MSH2 or (C) AQP5 and merged with DAPI staining. Scale bars: 100 μm. Representative images are a result of staining tumors from 2 cohorts described in the Methods, where experiments were done in triplicate from WT (n = 12) and DPEP1-KO (n = 10) tumors.

Fig 4: DPEP1 is a Wnt response gene and is associated with MSS CRC and related mutations.(A) Representative IHC staining of apical DPEP1 at the base of human normal colonic crypts. Scale bar: 100 μm. (B) Relative quantification for AXIN2, NKD1, and DPEP1 mRNA levels in normal colonic organoids with or without CHIR99021 (CHIR) treatment (n = 4 biological replicates). Error bars represent SEM. (C–F) DPEP1 mRNA expression of TCGA database COAD and READ cohorts as it relates to (C) APC (n = 274), (D) P53 (n = 356), (E) BRAFV600E (n = 344) mutational status, and (F) MSI-H status (n = 375). (G) Percentage of CRC samples from TMAs based on DPEP1 staining intensity as delineated by MSI status (n = 105). (H) DPEP1 mRNA expression of TCGA database COAD and READ cohorts as it relates to CRC CMS categories (n = 485). Median denoted in red. WT, wild-type; MUT, mutated; NS, no significance. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001 by Wilcoxon-Mann-Whitney, χ2 (B-F), chi squared (G), and Kruskal-Wallis test (H).

Fig 5: DPEP1 is linked to neutrophil presence and binding in CRC.(A) Hematoxylin and eosin (H&E) staining and DPEP1 and neutrophil elastase immunohistochemistry (IHC) for 2 selected cores from a human adenoma tissue microarray (TMA) (n = 336 cores assessed). (B) DPEP1 and neutrophil elastase IHC and H&E for a selected core from a human CRC TMA (n = 249 cores assessed). (C) Quantification of neutrophil binding assay for comparison of SW480 and SW620 cells, where each field of view (FOV) is an individual data point (n = 12 FOVs per cell type). (D) Quantification of neutrophil binding assay for SW620 cells treated with scrambled or LSALT peptide at the designated concentrations (μM) as indicated on the graph, where each FOV is an individual data point (n = 12 FOVs per condition). Data are representative images. Arrows mark individual cells positive for neutrophil elastase. Scale bars: 200 μm and 100 μm (insets). Binding assays were conducted in triplicate. Error bars represent SEM. NS, no significance. ***P < 0.001; ****P < 0.0001 by Wilcoxon-Mann-Whitney (C) andor Kruskal-Wallis test (D).