In the present study, cell lines representative of cancer types were selected as described previously (16 (link)): MCF7 and T47D for luminal A type; BT474 for luminal B type; and MDA-MB468, MDA-MB231, HCC70 and HCC1143 for TNBC. The human breast cancer cell lines were obtained from the Riken Cell Bank (MCF7; Riken BioResource Research Center, Tsukuba, Japan) and from the American Type Culture Collection (T47D, BT474, MDA-MB468, MDA-MB231, HCC70 and HCC1143; Manassas, VA, USA). Cells were cultured in RPMI-1640 medium (Wako Pure Chemical Industries, Ltd., Osaka, Japan) supplemented with 100 U/ml of penicillin, 100 U/ml of streptomycin and 10% fetal bovine serum (FBS; Gibco; Thermo Fisher Scientific, Inc., Waltham, MA, USA) in a humidified atmosphere containing 5% CO2 at 37°C.