The most frequent cancer in women to be diagnosed is breast cancer, and chemotherapy's ability to be effective is still significantly hampered by drug resistance. Tumor-derived exosomes play a significant role in drug resistance, immunological modulation, metastasis, and tumor proliferation. In this work, the differential miRNAs in the exosomes of drug-resistant and susceptible breast cancer cell lines were screened using miRNA-seq. It was demonstrated that drug-resistant human breast cancer cells and their exosomes expressed more miR-99b-3p than did susceptible cells and their exosomes. While drug-resistant cells' migration and paclitaxel resistance can be inhibited by driving down the expression of miR-99b-3p in those cells, exosomes containing miR-99b-3p from those cells can help susceptible cells migrate and become resistant. miR-99b-3p affects cell migration and paclitaxel resistance by targeting PPP2CA to promote AKT/mTOR phosphorylation. The drug-resistant cell exosome miR-99b-3p can be taken up by macrophages and affect the drug resistance and migration ability of sensitive cells by promoting the M2 polarization of macrophages. Downregulating miR-99b-3p has been shown in vivo to reverse macrophage M2 polarization, suppress tumor development, and prevent treatment resistance. The present study shows that drug-resistant cell exosomes miR-99b-3p can directly influence the migration, proliferation, and paclitaxel sensitivity of sensitive cells via PPP2CA. Additionally, the exosomes from drug-resistant cells can influence the polarization of macrophage M2 in the tumor microenvironment, which can also have an impact on the proliferation, migration, and paclitaxel sensitivity of sensitive cells.
Keywords: Breast cancer; Exosomes; Metastasis; Paclitaxel resistance; Polarization; miR-99b-3p.
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