From Normal Mucosa to Colorectal Cancer in Lynch Syndrome: Single-Cell Dissection of Cellular Heterogeneity and Communication Networks.

OBJECTIVETo generate a single-cell atlas of colorectal cancer (CRC) development in Lynch syndrome (LS), and to delineate the associated cellular reprogramming and intercellular communication networks.

METHODSWe performed single-cell RNA sequencing (scRNA-seq) on matched normal mucosa, adenoma, and carcinoma tissues obtained from patients with LS. Following quality control and batch-effect correction, we used the Uniform Manifold Approximation and Projection (UMAP) clustering and marker gene analyses to annotate cell types, differential expression analyses to identify stage-specific genes, and GSVA analyses to assess pathway activity. Functional assays with patient-derived organoids and transwell experiments were employed to validate the role of DMBT1. Cell-cell communication networks were inferred using Cell Chat.

RESULTSWe identified twelve distinct cell clusters and observed marked shifts in cellular composition during CRC progression, including increased T lymphocytes and macrophages and decreased epithelial cells. Trajectory analyses suggested a potential differentiation path from BEST4+ to CEMIP+/EGFR+ epithelial cells. DMBT1 was consistently down-regulated and its depletion activated the WNT/β-catenin pathway, enhancing organoid growth and cell migration. Expansion of CCR8+ regulatory T cells and C1QC+/IDO1+/IL1B+ macrophages indicated an immunosuppressive and pro-tumorigenic microenvironment.

CONCLUSIONSThis study provides a comprehensive single-cell resource for LS-associated CRC and highlights DMBT1 loss, epithelial remodelling, and immune dysregulation as potential therapeutic targets.