Extracellular Vesicles Carrying miR-887-3p Promote Breast Cancer Cell Drug Resistance by Targeting BTBD7 and Activating the Notch1/Hes1 Signaling Pathway

Abstract

Objective. Chemoresistance remains the primary reason threatening the prognosis of breast cancer (BC) patients. Extracellular vesicles (EVs) contribute to chemoresistance by carrying microRNAs (miRNAs). This study investigated the mechanism of miR-887-3p mediated by EVs in BC cell drug resistance. Methods. MDA-MB-231-derived EVs were extracted and identified. BC cells were treated with different concentrations of doxorubicin, cisplatin, and fulvestrant, and the cell survival was evaluated. PKH26-labeled EVs were cocultured with BC cells, and the uptake of EVs was observed. miR-887-3p expression in BC cells and EVs was detected. After silencing miR-887-3p in MDA-MB-231 cells, BC cells were treated with EV-inhi to observe drug resistance. The target gene of miR-887-3p was predicted and verified. The levels of downstream Notch1/Hes1 pathway were detected. Xenograft experiment was conducted to evaluate the effect of EVs on the growth and drug resistance in vivo. Results. MDA-MB-231-derived EVs enhanced the drug resistance of BC cells. EVs carried miR-887-3p into BC cells. miR-887-3p expression was elevated in BC cells and EVs. miR-887-3p inhibition reduced the drug resistance of BC cells. miR-887-3p targeted BTBD7. Overexpression of BTBD7 partially reversed the drug resistance of BC cells caused by EV treatment. EV treatment increased the level of Notch1/Hes1, and overexpression of BTBD7 decreased the level of Notch1/Hes1. In vivo experiments further validated the results of in vitro experiments. Conclusion. EVs carrying miR-887-3p could target BTBD7 and activate the Notch1/Hes1 signaling pathway, thereby promoting BC cell drug resistance. This study may offer novel insights into BC treatment.