Fig. 1

BT474 cells are resistant to tamoxifen. a Characterization of BT474 and T47D cells. Western blot analysis of ER, HER2, PR, and c-Src and their phosphorylation status in both cell lines, and Actin is as a loading control. b BT474 and T47D cells were seeded in 96-well plates at a density of 5000 cells/well and then treated with 4-OH tamoxifen (0–10 μmol/L). After 3 days, MTT assays were performed. c BT474 and T47D cells were seeded in 96-well plates and 24 h after plating, cells were treated with vehicle (CON), 17β-E2 (E2) (10 nmol/L), tamoxifen (TAM) (1 μmol/L), or combination (E2/TAM). After 48 h, MTT assays were performed. The bar graph shows the sensitivity of cells to the indicated treatments. Data represent the mean ± SD of at least three independent experiments. d Effect of tamoxifen on colony formation in BT474 cells. After 14 days, colonies in 6-well plates were imaged and quantified by counting the number of colonies. At least nine wells per treatment group were quantified per value reported. The results show the mean from three independent experiments. *P < 0.05