Establishing Triple-Negative Breast Cancer Model

The human breast cancer cell line HCC1937 was purchased from American Type Culture Collection (ATCC). The HCC1937 cells were negative for expressions of ER, PR, and HER2, referred to as a triple-negative tumor, and had mutations of TP53 and BRCA1 [24 (link)]. HCC1937 cells were stably transfected with a wt-p53-inducible plasmid (Tet-on Advanced System, Clontech, USA), and one of the isolated clones was designated as HCC1937/p53 and used for the experiments. The HCC1937/p53 cells were cultured in RPMI1640 (Nacalai Tesque, Kyoto, Japan), containing 10% fetal bovine serum (FBS) (SIGMA, USA) [18 (link)], and Zeocin^TM (1 μg/mL, InvivoGen, USA). The HCC1937/p53 cells were cultured in doxycycline (Takara, 1 ng/mL)-containing media for 1–7 days, and those cells treated with doxcycline for 2 days were designated as Dox2d [20 (link)].