Background. Tumorigenesis in the right-sided and left-sided colon demonstrated distinct morphology and molecular features. However, little is known about the impact of anatomical location of colon adenoma on its interaction with the tumor microenvironment in facilitating tumorigenesis. Here, we delineated the tumor microenvironment of right-sided colon adenoma and identified S100A11 as a potential target for immunotherapy.

Methods. Two published single-cell sequencing datasets were analyzed to reveal cellular alternation in right-sided and left-sided colon adenoma. Spatial transcriptomics (n=2) was performed in right-sided and left sided colon adenomas. qPCR, immunohistochemical staining and fluorescence in situ hybridization were used to detect the existence of bacteria. Bacterial components lipopolysaccharide (LPS) and peptidoglycan (PGN) were utilized to treat organoids from Apc^Min/+ mouse adenoma. Immune cell infiltration was determined by flow cytometry.

Results. Single-cell analysis revealed that in right-sided adenoma, there was significant reduction in proportion of goblet cells, and these goblet cells were dysfunctional with attenuated mucin biosynthesis and defective protein glycosylation and secretion pathways. In contrast, T cells expressing antimicrobial peptides (CST3 and DEFA5) and galectin (LGALS3 and LGALS4) were enriched, together with the appearance of a distinct S100A11⁺ epithelial cell population in the right-sided colon adenoma. Spatial transcriptomics validated that right-sided colon adenomas harbored elevated inflammatory signaling and reduced mucus-producing cells. Accordingly, impairment of mucus barrier led to translocation of bacteria into right-sided colon adenomas. We demonstrated that bacterial LPS and PGN up-regulated S100A11 expression in the right-sided colon adenoma. Overexpression of S100A11 facilitated the tumor growth of adenoma organoids (p<0.05) and CT26 (p<0.01) allografts in syngeneic immunocompetent mice, but not in immunodeficient mice, suggesting the role of S100A11 in modulating tumor immunity. Indeed, S100A11-expressing tumors had increased myeloid-derived suppressor cells (MDSCs) (p<0.05) but reduced cytotoxic CD8⁺ T-cells (p<0.05). Targeting of S100A11 with neutralizing antibody or antagonists of its receptor RAGE ((FPS-ZM1 and Azeliragon) significantly impaired tumor growth (p<0.05) and MDSC infiltration (p<0.05). Finally, Azeliragon boosted anti-PD1 efficacy in colon cancer, suggesting that it could be repurposed to improve immunotherapy efficacy.

Conclusion. Our findings unraveled that dysfunctional goblet cells and consequential bacterial translocation activated S100A11-RAGE axis in in right-sided colon adenomas, which recruits MDSCs to promote immune evasion. Targeting this axis by Azeliragon improves the efficacy of immunotherapy in colon cancer.

Xiaowu Bai

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