Exosome-Derived MicroRNA-221-3p Desensitizes Breast Cancer Cells to Adriamycin by Regulating PIK3r1-Mediated Glycose Metabolism

Background: Cancer-derived exosomes facilitate chemoresistance by transferring RNAs, yet their role in exosomal microRNA-221-3p (miR-221-3p) regulation of Adriamycin resistance in breast cancer (BC) remains unclear. Methods: Adriamycin-resistant BC cells were developed from MCF-7 and MDA-MB-231 cells by incremental Adriamycin exposure. The miR-221-3p levels were quantified by quantitative reverse transcription-polymerase chain reaction. Subsequently, exosomes were isolated and incubated with BC cells, and exosome-mediated Adriamycin sensitivity was evaluated using Cell Counting Kit-8, colony formation, and flow cytometry assays. Sensitive cells were cocultured with miR-221-3p inhibitor-treated cells to assess Adriamycin resistance. Moreover, the interaction between miR-221-3p and phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) was validated using a dual luciferase reporter gene assay. Mimics and inhibitors were used to determine the effects of miR-221-3p on Adriamycin resistance. Results: Elevated levels of miR-221-3p expression were observed in Adriamycin-resistant BC cells and exosomes. Sensitive cells were cocultured with exosomes from resistant cells, resulting in increased half-maximal inhibitory concentration value and proliferation, and reduced Adriamycin-induced apoptosis. However, the effects of coculturing sensitive cells with Adriamycin-resistant cells were significantly weakened by miR-221-3p inhibitor transfection in Adriamycin-resistant cells. PIK3R1 was found to be a target of miR-221-3p, and miR-221-3p mimics enhanced Adriamycin resistance in sensitive cells. miR-221-3p inhibitors increased the expression of PIK3R1, p-AKT, c-Myc, HK2, and PKM2, decreased FOXO3 expression, and weakened the Adriamycin resistance in resistant cells. Conclusions: miR-221-3p can be transferred between BC cells through exosomes. High levels of miR-221-3p were found to target PIK3R1 and promoted Adriamycin resistance in BC cells.