Ononin Synergistically Enhances the Cytotoxic Effect of Doxorubicin in MDA-MB-231 Triple Negative Breast Cancer Cell Line

Triple-negative breast cancer (TNBC) accounts for approximately 15% of global breast cancer incidence. The disease is characterized by aggressive characteristics, unfavorable outlook, and a higher rate of recurrence. The absence of estrogen receptor alpha renders hormonal therapies ineffective. Chemotherapy remains the standard approach for treatment. However, it has severe side effects. This research explores the cytotoxic activity of Ononin against TNBC in vitro and its ability to enhance the chemosensitivity of doxorubicin (DOX) on MDA-MB-231 cells. The impact of Ononin as well as Ononin-DOX combination on cytotoxicity, migration, colony formation, and apoptosis were investigated. Ononin exhibited cytotoxic effect against MDA-MB-231 cells, with an IC ₅₀ of 52 µM, while DOX had an IC ₅₀ of 1.8 µM. Noteworthy, combining Ononin with DOX led to reduction in the ED ₇₀ , ED ₇₅ , and ED ₉₀ of DOX against MDA-MB-231 cells by 1.34-fold, 2.68-fold, and 55-fold, respectively. Combining 0.45 µM of DOX with 6 µM of Ononin resulted in a notable decrease in colony formation compared to 0.45 µM of DOX alone (p < 0.0001). Ononin exhibited strong anti-migratory effects. When combined with DOX, it significantly reduced cell migration compared to DOX (0.45 µM) alone after 72 hours (p < 0.05). On the other hand, Ononin (25 µM) had no effect on the expression of caspase 3 gene in these cells. It stands out as the first study to show that Ononin, as a standalone agent, reduces MDA-MB-231 cell viability, migration and colony formation. Additionally, it synergistically enhances the cytotoxic effects of DOX.