Extracellular circular RNAs to promote the growth and metastasis of triple-negative breast cancer through remodeling the tumor immune microenvironment.

Abstract

e13047 Background: Triple-negative breast cancer (TNBC) has been confirmed to have a high degree of heterogeneity of breast cancer, which is more common in young women, with a high degree of malignancy, lack of effective clinical treatment and poor prognosis. Recently, many studies have also found that immune microenvironment (IME) can remarkablely affect the occurrence and metastasis of TNBC through exosome-mediated molecular transmission. Therefore, there is an urgent need to find new immune-related molecules as therapeutic targets and to predict the progress of TNBC and prognosis of treatment. Methods: Using RNA-sequencing and bioinformatics analysis, we found the differential-expressed circular RNAs (circRNAs) in exosomes from TNBC cell lines (BT549 and MDA-MB-231), non-TNBC cell lines (MCF-7 and MCF-10A) and tissues from breast cancer patients. Then, we used CIBERSORT and ESTIMATE algorithm to explore the tumor-infiltrating immune cells (TICs) or stromal components in IME, and identified the significant differential-expressed mRNAs in the immune cells between TNBC and non-TNBC samples. RT-qPCR was used to confirm the expression level of selected circRNAs and mRNAs in TNBC cell lines. Results: We profiled the circRNAs in the exosomes from TNBC cell lines and breast cancer patients by RNA sequencing and detected 27 significantly differentially-expressed circRNAs. After bioinformatic analysis and RT-qPCR, circRELB and circANXA1 were chose to further study. TICs and IME scores were found to associated with the survival and clinicopathological characteristics of TNBC patients and IME remodeling. Interestingly, 92 differentially-expressed genes were found to be enriched in the NF-kB signaling pathway and mTOR signaling pathway. Moreover, we identified 33 target genes of circRELB and circANXA1 by cross-analysis. Based on the predicted miRNAs and the corresponding mRNAs and circRNAs, we have established an IME-related circRNA-miRNA-mRNA network. Then, Kaplan-Meier plots showed the expression levels of certain targeted genes (PTEN, CCND1, IL6, CDKN1A, AKT1, TNF and WNT1) were connected to prognosis in TNBC metastasis patients. Conclusions: The expression levels of circRELB and circANXA1 was found significantly upregulated in exosomes from TNBC cell lines and tumor tissues from breast cancer patients. In addition, circRELB and circANXA1could affect the expression of downstream target genes by competing for endogenous RNA (ceRNAs), and ultimately promote the metastasis of TNBC and remodeling of IME. In summary, this study analyzes the mechanisms of exosome-contained circRNAs in TNBC and these targets from the IME-related circRNA-miRNA-mRNA network may be new potential prognostic biomarkers and immune treatment strategies to prevent the development and metastasis of TNBC.