Figure 3. Resveratrol triggers HER2 over-expression and ERα down-regulation in luminal B breast cancer cell lines. (a) CAM6 and (b) BT474 cells were incubated for 24 hours in the presence of vehicle or increasing concentrations of resveratrol and cell viability was determined by MTT assay. Results (including vehicle group treated with 0.02% DMSO) are expressed as percentage (%) of cell viability relative to untreated controls. Columns, mean of three separate experiments wherein each treatment was repeated in 16 wells; bars, SE. **p ≤ 0.01, ***p ≤ 0.001, one-way ANOVA followed by Bonferroni's multiple comparison test. Representative western blot analysis of HER2, ERα and β-actin (loading control) in murine CAM6 cells (c) or human BT474 cells (d), treated with resveratrol or 17β-estradiol or vehicle for 24 hours (upper panel), and relative densitometry quantification (lower panel). The significance was determined by one-way ANOVA (*p < 0.05, **p ≤ 0.01).