Mda mb 231

Normal breast epithelial cells (MCF‐10A) and BC cells (MCF‐7 and MDA‐MB‐231) were purchased from the American Type Culture Collection (ATCC, Manassas, VA, USA). PTX‐resistant BC cells (MCF‐7/PTX and MDA‐MB‐231/PTX) were established by treating MCF‐7 and MDA‐MB‐231 cells with rising concentrations of PTX (Sangon, Shanghai, China) at an initial concentration of 0.5 nM PTX. After the cells had grown steadily at each PTX concentration condition, PTX concentration was increased and the culture continued until the cells had grown steadily in the medium containing 5 nM PTX. The process lasted for three months. All cells were maintained in Roswell Park Memorial Institute 1640 Medium (Thermo Fisher Scientific, Waltham, MA, USA) including 10% fetal bovine serum (FBS; Gibco, Grand Island, NY, USA) and 1% penicillin‐streptomycin (Solarbio; Beijing, China) at a condition of 5% CO₂ and 37°C. To maintain the resistance of PTX‐resistant BC cells, the culture medium was added with 5 nM PTX (Sangon) until two weeks before further experiments.

The normal breast epithelial cells MCF-10A and the breast cancer cell lines MDA-MB-468, MDA-MB-231 and MCF-7 were obtained from the American Type Culture Collection. MCF-10A cells were cultured in MEGM (Cobioer Biosciences) with 100 ng/ml cholera toxin. MDA-MB-468, MDA-MB-231 and MCF-7 cells were cultured in DMEM (Sangon Biotech Co., Ltd.) supplemented with 10% fetal bovine serum (Sangon Biotech Co., Ltd.) and 1% antibiotics (penicillin 100 U/ml; streptomycin 100 µg/ml; Sangon Biotech Co., Ltd.). All cell lines were cultured in an incubator at 37°C with 5% CO₂.