Single-Cell RNA Sequencing Reveals Characteristics of Myeloid Cells and Fibroblasts in RAS-Mutated Colorectal Cancer

Background RAS -mutated (RAS-mut) colorectal cancer (CRC) has poor prognosis and is resistant to immune therapies. Therefore, understanding the mechanism of immune evasion in RAS-mut CRC is crucial for developing new therapeutic targets. Methods A total of 36 clinical surgical samples (tumors and paired adjacent tissues) from 18 patients with primary CRC were collected for single-cell transcriptome sequencing. All cells were divided into two groups according to their RAS-mut status. Differential enrichment, CellChat, and pySKEEN transcription factor analyses were performed to identify cells with different functions in the RAS-mut group. The results were validated using The Cancer Genome Atlas public database and immunofluorescence staining. Results Overall, 214,316 individual cells underwent single-cell RNA-sequencing analysis. We identified a subpopulation of CD1C + type II conventional dendritic cells (cDC2-CD1C) exhibiting a higher infiltration and associated with immune resistance in RAS-mut CRC. In contrast, pericytes demonstrated reduced infiltration and may affect the prognosis of RAS-mut CRC. A subpopulation of CXCL14 + matrix tumor-associated fibroblasts (mCAF-CXCL14) exhibited a slightly higher infiltration ratio in the RAS-mut environment, potentially interacting with cDC2-CD1C to promote tumor malignant behavior. Conclusion Our study identifies differences in the infiltration ratios and possible functional characteristics of myeloid cells (cDC2-CD1C) and fibroblasts (mCAF-CXCL14 and pericytes) in RAS-mut CRC. The unique biological role of these cells in the RAS-mut tumor microenvironment underlies a worse clinical prognosis compared to wild-type CRC. Furthermore, specific cellular interactions within RAS-mut CRC may provide new therapeutic targets and offer potential strategies for enhancing immunotherapy efficacy.