miR-125b regulates the drug-resistance of breast cancer cells to doxorubicin by targeting HAX-1.

MircroRNAs (miRNAs) are considered as essential regulators in the tumorigenesis and chemoresistance of multiple cancer types. In the present study, it was demonstrated that the expression levels of miR-125b were significantly downregulated in the tissues of patients with breast cancer (BC), as well as the BC cell lines in vitro . To study the association between chemoresistance and miR-125b in BC, doxorubicin (DOX)-resistant MCF-7 (MCF-7/R) cells were established, and gain- and loss-of-function experiments were performed. It was demonstrated that the overexpression of miR-125b increased the sensitivity of MCF-7/R cells to DOX. Furthermore, it was revealed that the sensitization of miR-125b mimics to DOX-induced cell death was regulated by the hematopoietic cell-specific protein 1-associated protein X-1 (HAX-1) vector and HAX-1 small interfering RNA. These results emphasized the notable function of miR-125b and its target of HAX-1 in regulating DOX-resistance. In addition, it was demonstrated that the miR-125b mimics promoted the loss of the mitochondrial membrane potential and the generation of reactive oxygen species induced by DOX treatment in MCF-7/R cells. These data suggest that the miR-125b-HAX-1-mitochondria pathway has a notable function in the treatment of DOX-resistant BC cells, which may provide a novel target for the chemotherapy of BC.