Effects of EVOO phenolics on breast cancer cell viability. MCF-7, MCF-7/(pBABE)HER2 and SKBR3 cells were incubated with various concentrations of tyrosol (A), hydroxytyrosol (B), oleuropein aglycone (C) and oleuropein glycoside (D) for 5 days. Cell growth, measured using MTT assay, was expressed as % of untreated cells (blue line = 100% cell viability). Results are means (columns) and 95% confidence intervals (bars) of three independent experiments made in triplicate. Statistically significant differences (one-factor ANOVA analysis) between experimental conditions and unsupplemented control cells are shown by asterisks (* P < .01, ** P < .001). All statistical tests were two-sided.