Using HER2-overexpressing BT-474 cells as a breast cancer model naturally enriched with ALDH1+ cells, we detected a significant decrease (up to 63% reduction) in the number of ALDH1+ cells when BT-474 cells were treated with a non-cytotoxic concentration (10 μmol/L) of CHEMBL1950046 (hydroxytyrosol butyrate). Here, ALDH1A1 is linked to breast cancer.