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e12500 Background: Anthracycline is widely used in breast cancer (BCa) chemotherapy, but acquired drug resistance remains a challenge. Increasing evidence suggests that changes in the tumour immune microenvironment (TIME) consistently contribute to the development of chemoresistance. Methods: TIME scores and tumor-infiltrating immune cells (TICs) scores were used to investigate the prognosis, characteristics and gene transcriptomic profiling of HER2-negative BCa patients who received anthracycline chemotherapy. Exosomes from MCF/7-ADR (ADR-exos) and MCF/7-S cell lines were characterized. Dysregulated miRNAs were obtained by using miRNA microarray analysis on BCa cells and their corresponding exosomes. Protein profiling was performed to identify differentially expressed proteins in up- and down-regulated miR-222 cells. Ability of ADR-exos to transfer drug-resistance mediated by miR-222 was assessed by immunofluorescence assay and flow cytometry. Conditions to load miR-222 mimic or inhibitor into exosomes were optimized. Influence of miR-222 inhibitor-containing exosomes on the downstream pathway of miR-222 and the potential therapeutic effects were evaluated. Relationship between miR-222/PTEN and drug resistance in circulating exosomes from mice after doxorubicin chemotherapy was investigated. Results: Firstly, we discovered the complicated and heterogeneous TICs subtypes and their unique biological behaviors in HER2-negative BCa. Then, we identified 85 differentially expressed immunologic signature gene sets and 7202 corresponding immune-related genes in three subtypes quantified by gene set variation analysis. We identified 12 up-regulated and 13 down-regulated genes using miRNA microarray analysis in doxorubicin-resistant cells and their exosomes. Mass spectrometry found 45 differentially expressed proteins affected by miR-222. Moreover, we successfully established miRNA mimic/inhibitor-containing exosomes to explore the solo function of exosomal miR-222 in doxorubicin-resistance both in vitro and in vivo. For the first time, we detected the levels of miR-222 and its target gene PTEN in circulating exosomes from mice after doxorubicin-based chemotherapy and explored the potential clinical implications of miR-222/PTEN-containing exosomes in chemotherapy and immune suppression of BCa. Conclusions: Doxorubicin-resistant cells can transmit drug-resistance to sensitive cells via delivering miR-222 by modulating the immune- and metabolism-related gene PTEN without interference from other relevant drug-resistance factors in exosomes. Therefore, miR-222-containing exosomes and their target gene PTEN may be a promising biomarker for predicting chemotherapy efficacy and tumor immunity regulation in BCa patients receiving anthracycline chemotherapy.
Yang et al. (Sat,) studied this question.