Hypoxia is a major hallmark of solid tumors and is associated with malignant phenotypes. Exosomal miRNAs derived from hypoxia tumor cells are implicated in the modulation of cancer progression, whereas, the mechanisms underlying the association between hypoxia and exosomal miR-25-3p during breast cancer progression remain to be further clarified. The present study aimed to investigate the role of exosomal miR-25-3p in regulating breast cancer progression. Herein, we found that miR-25-3p expression was increased in hypoxia tumor-derived exosomes a HIF-1α-dependent manner. Hypoxia exosomes markedly stimulated the viability and migration of normoxia breast cancer cells, which was reversed by miR-25-3p depletion. Inhibition of exosomes miR-25-3p lowered hypoxic-induced the expression of IL-6 and NF-κB from THP-1 and RAW264.7 cells in a TLR7/8-dependent way. Treatment of macrophage supernatant (MS) initially incubated with hypoxic-responsed exosomes accelerated the viability and migration of breast cancer cells, and miR-25-3p depletion relieved the stimulatory effects of hypoxic on cell viability and migration. Moreover, miR-25-3p knockdown dramatically suppressed HIF-1α-induced tumor growth in vivo via inactivation of IL-6/STAT3 signaling pathway, reflected by the abated abundances of IL-6 and p-STAT3. These data suggested that absence of exosomal miR-25-3p rescued breast cancer aggressiveness through inhibiting cell viability and migration by regulation of IL-6 secretion from macrophages, providing a potential biomarker for breast cancer treatment.
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