Abstract Extra virgin olive oil, a foundational element of the Mediterranean cuisine, has been widely associated with numerous health benefits, including the prevention of degenerative diseases and the promotion of longevity. A major bioactive component of the olive tree is oleuropein, a phenolic compound predominantly found in olive leaves and fruit. Oleuropein has been well-characterized for its potent antioxidant and anti-inflammatory properties, as well as its potential anticancer effects demonstrated in both animal and cell-based models. In this study, we investigated the effects of oleuropein on the human triple-negative breast cancer cell line MDA-MB-231. Cells were treated with oleuropein at concentrations of 50, 200, and 400 µg/mL, or 70% ethanol control. We assessed cell viability using the MTS assay, and cytotoxicity and apoptosis using a Caspase 3/7 activity. We found the highest concentration of oleuropein to induce a 3-fold decrease in viable cell density and an 8-fold increase in apoptosis. We also examined the effect of oleuropein on the expression of the peroxiredoxin (Prdx) gene family, which encodes thiol-specific antioxidant proteins known to protect cells from oxidative damage and that we previously demonstrated to be induced by oleuropein in MCF-7 cells. We found significant induction of Prdx gene expression in MDA-MB-231 cells by oleuropein, with a marked induction of Prdx1 with the 400 ug/ml treatment. Current research is aimed at measuring Prdx protein expression in oleuropein-treated cells, as well as the effect of Prdx suppression on oleuropein susceptibility. Together, these findings suggest that oleuropein exerts dose-dependent anticancer effects in MDA-MB-231 cells that result in a robust peroxiredoxin antioxidant protein response. Further exploration of the mechanism of action of oleuropein in MDA-MB-231 cells will provide important insights into its pro-oxidant effects and potential therapeutic applications. Citation Format: Giovanna Kalin, Adam Vaz, Shelley A. Phelan, . Oleuropein, a phenolic compound from olive leaves, exerts cytotoxicity and peroxiredoxin induction in MDA-MB-231 breast cancer cells abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3665.
Kalin et al. (Fri,) studied this question.