Ham s f12 medium

Breast cancer cell lines were purchased from the Korean Cell Line Bank (Seoul, Korea). MCF10A and MDA-MB-453 cells were obtained from the American Type Culture Collection (ATCC; Manassas, USA). Non-tumorigenic mammary epithelial MCF10A cells were cultured in a 1:1 mixture of Dulbecco’s modified Eagle’s medium (DMEM; Biowest, Riverside, USA) and Ham’s F12 medium (Biowest), containing 5% horse serum (Gibco, Waltham, USA), 20 ng/mL epidermal growth factor (EGF; Sigma-Aldrich, St. Louis, USA), 10 μg/mL insulin (Sigma-Aldrich), and 500 ng/mL hydrocortisone (Sigma-Aldrich). MCF7, MDA-MB-231, MDA-MB-468, HS578T, and T47D cells were cultured in DMEM supplemented with 10% fetal bovine serum (FBS; Gibco) and 1% penicillin/streptomycin (Gibco). SK-BR3, ZR-75-1, BT474, MDA-MB-453, BT20, HCC38, and HCC70 cells were maintained in RPMI 1640 (Biowest) supplemented with 10% FBS and 1% penicillin/streptomycin. For the siRNA experiments, commercially available PLK1 (Gene ID: 5347) siRNA was purchased from Dharmacon Inc. (Lafayette, USA). Cells were transfected with siRNA (10 nM) using the ON-TARGETplus human PLK1 siRNA-SMARTpool siRNA transfection reagent (Dhamacon Inc.), according to the manufacturer’s instructions.