Dissecting the cellular reprogramming and tumor microenvironment in left- and right-sided Colorectal Cancer by single cell RNA sequencing

Sidedness and staging are major sources of tumor microenvironment (TME) differences in colorectal cancer (CRC). Subpopulation compositions of stromal cells and immune cells, and interactions between cells collectively constitute the immunosuppressive microenvironment of CRC. In this study, we comprehensively collected single-cell RNA sequencing data from public databases. We filtered out 126,279 cells from 55 CRC samples to characterize the differences in cellular composition, and to elucidate the transcriptional features and potential functions of cell types, temporally and positionally. We observed an increased degree of hypoxia in right side-specific cancer cells compared to left-sided cancer. Cancer-associated fibroblasts (CAFs) illustrated molecular signatures tremendously tended to be associated with functions that orchestrate extracellular matrix remodeling and angiogenesis, and right-sided CAFs characterized the stronger cancer invasion signals. Crosstalk between side-specific cancer cells and stromal together with immune cells characterized CRC via different sample groups, and was pertinent to worse prognosis. Our study captured immunosuppressive pattern exhibiting more intricate intercellular interactions in right-sided CRC. Additionally, during malignant progression of CRC, the transformation of CD8+ T cell cytotoxic and exhausted properties and macrophage pro-inflammatory and anti-inflammatory properties epitomized the cellular reprogramming phenomenon that the function of TME shifted from promoting immunity to suppressive immunity. Our study shed lights on refining personalized therapeutic regimens during malignant progression in left- and right-sided CRCs.