Impact of cancer-associated fibroblasts on immunotherapy and liver metastasis in colorectal cancer
Objective To investigate the impact of cancer-associated fibroblasts(CAFs)on immunotherapy and liver metastasis in colorectal cancer(CRC).Methods The single-cell sequencing data(GSE205506)of CRC patients with mismatch repair deficiency(MMRd)were downloaded from the gene expression omnibus database,and R software was used to preprocess the original sequencing data and establish the umap of fibroblast subpopulations,with each subpopulation named based on signature genes.GraphPad was used for the statistical analysis of the proportion of each fibroblast subpopulation,and the key subpopulations with significant differences were analyzed among CRC patients before and after PD-1 immunotherapy,as well as between the patients with pathological complete response(pCR)and those without pCR(non-pCR)after treatment.The analysis of differentially expressed genes and the gene pathway enrichment analysis were performed for the key subpopulations.The TCGA database was used to perform a prognostic and survival analysis of the signature genes of key CAF subpopulations,and RNA sequencing data were used to score and calculate the proportion of key CAF subpopulations in the primary lesions of CRC patients with liver metastasis.The independent-samples t test was used for comparison of normally distributed continuous data between two groups;the Kaplan-Meier method was used to plot survival curves,and the log-rank test was used to calculate survival rates.CellPhoneDB software was used to analyze the receptor-ligand interaction between fibroblast subpopulations and tumor cells,and in vitro cell experiments were used to validate the effect of NRG1,a key ligand molecule,on the migration and invasion abilities of CRC cells.Results After PD-1 immunotherapy for CRC patients,there was a significant reduction in the proportion of F6_MMP1+CAFs(P＜0.001),which was only observed in patients achieving complete remission after immunotherapy.F6_MMP1+CAFs were upregulated,as well as the genes and signaling pathways associated with tumor migration and invasion,and in addition,there was a significant increase in F6_MMP1+CAFs in the tumor tissue of CRC patients with liver metastasis(P＜0.000 1).As a ligand,NRG1 expressed by F6_MMP1+CAFs interacted with ERBB3 receptor expressed by tumor cells,and the in vitro experiments confirmed that NRG1 promoted the migration and invasion abilities of tumor cells by activating the ERBB signaling pathway(P＜0.05).Conclusion F6_MMP1+CAFs may affect the efficacy of PD-1 immunotherapy in CRC patients and play an important role in promoting liver metastasis in CRC.F6_MMP1+CAFs,along with NRG1 that is produced by them and can promote tumor metastasis,can be used as potential therapeutic targets and prognostic markers for CRC.
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