The anti-tumor effects of four representative EVOO phenolics were initially assessed by characterizing the metabolic status of MCF-7, MCF-7/HER2 and SK-Br3 breast cancer cell lines treated with micromolar concentrations (6.25 → 100 μM) of tyrosol, hydroxytyrosol, oleuropein aglycone, and oleuropein glycoside. This evidence concerns the gene ERBB2 and breast carcinoma.