GSIXII induced apoptosis in ER+ or ER- / HER2- breast cancer cell lines. (A) MDAMB231 cells were treated with increasing GSIXII doses and analyzed with flow cytometry after Apo2.7 immunostaining. Data represent (percentage of Apo2.7-positive cells) and the means ± standard errors (SEM) of three independent experiments. (B) Three ER+ human breast cancer cell lines (ZR75.1, T47D, and MCF7) and three ER-/HER2- (BT549, Cal51, and MDAMB231) were treated with GSIXII, 15 μM, for 48 hours and then analyzed with flow cytometry after Apo2.7 immunostaining. Represented data are the means ± SEM of three independent experiments.