| Triple negative breast cancer(TNBC)is the most aggressive subtype of breast cancer,with negative expression of Estrogen receptor(ER),Progesterone receptor(PR),and Human epidermal growth factor receptor 2(HER2).In clinical terms,TNBC lacks a clear therapeutic target and is prone to recurrence and metastasis,thus usually causing a poor prognosis and low survival rate for patients.Tumor microenvironment(TME)refers to the collection of the growth environment and various normal cell types around tumor cells,mainly including mesenchymal cells and immune cells infiltrating in tumor tissues,which play a key role in tumor progression.With the development of single-cell RNA-sequencing(sc RNA-seq)technology,it is possible to reveal the heterogeneity within TME at the single-cell level,such as exploring the composition of immune cells,identifying rare cell subpopulations,etc.Single-sample gene set enrichment analysis(ss GSEA)and cell communication analysis were utilized to analyze the data of GSM4476488 sample in Gene Expression Omnibus(GEO)database.The heterogeneity within the epithelial cells was explored and the vital subpopulations were identified.The results showed that there is a normal subpopulation with positive expression of estrogen receptor 1(ESR1)in epithelial cells,which regulates gene expression of other cells and is involved in biological processes such as estrogen response and tumor metastasis,which may be a potential target for drug therapy.In addition,three tumor subpopulations that may be in a mitotic state and one that is significantly enriched in hypoxia gene sets were identified.It was found that among the 8 signaling pathways mainly involved in hypoxia-related tumor subpopulation through secreting ligands,the CALCR,VEGF,EDN,ANGPTL,GDNF,and L1CAM pathways have been confirmed to be related to the process of promoting angiogenesis or tumor metastasis.The expression levels of ADM,VEGFA,EDN1,ANGPTL4,ARTN and L1CAM ligands involved in these pathways were significantly up-regulated in this subpopulation.Therefore,it is speculated that this subpopulation has a role in promoting tumor development under hypoxia,which may be related to the poor prognosis of patients.The gene expression and clinical data of TNBC patients were obtained from The Cancer Genome Atlas(TCGA)database,and the risk factors ARTN and L1CAM leading to poor prognosis were identified by survival analysis,and the risk score model was constructed based on these two genes,which achieved a good effect in predicting the survival status of patients.In addition,the composition of immune cells within TME and its correlation with prognosis were investigated by immune cell infiltration analysis.The results showed that there were significant variations in the infiltration levels of various immune cells in TNBC,which may be accompanied by phenotypic transformation,such as the polarization of macrophages and activation of CD4~+memory T cells.Among them,the infiltration levels of activated CD4~+memory T cells and regulatory T cells were significantly correlated with patient prognosis,while the infiltration levels of macrophages M0,CD8~+T cells and follicular helper T cells were significantly different in the high-and low-risk groups.In addition,hypoxia related genes such as ADM,VEGFA,ARTN and L1CAM were significantly positively correlated with the infiltration level of macrophages M0,suggesting that hypoxia plays a certain role in regulating the phenotypic transformation of macrophages.Finally,the expression of ARTN and L1CAM was found to be correlated with the survival of patients in a variety of cancers including TNBC through extensive cancer analysis.In conclusion,through in-depth exploration of TME,the mechanism of tumor development in TNBC was revealed,and the hypoxic tumor subpopulation and its prognostic marker genes ARTN and L1CAM were identified.This subpopulation plays a key role within TME,and its biological function and influence needs further exploration. |
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