Curcumin-Etoposide Synergy: Unveiling the Molecular Mechanisms of Enhanced Apoptosis and Chemoresistance Attenuation in Breast Cancer.

Background: Combining natural compounds with chemotherapeutic agents has emerged as a promising approach for cancer treatment. Curcumin (Cur), a natural polyphenol, is known for its anti-cancer properties, including the ability to induce apoptosis and arrest cell cycle progression.

Objectives: This study aimed to evaluate the effects of Cur and etoposide (ETO), both individually and in combination, on the induction of apoptosis in breast cancer (BC) cell lines.

Methods: The impact of Cur and ETO on cell proliferation was assessed using MTT viability assays. Apoptosis induction by these drugs was evaluated through Annexin V flow cytometry and caspase-3 and caspase-9 activity assays. Quantitative real-time PCR was employed to measure Bax and Bcl-2 gene expression levels. Western blotting was conducted to determine protein levels of p53, p21, Bax, and Bcl-2.

Results: A non-significant dose of ETO was selected based on MTT assay results and combined with 75 µM of Cur. Curcumin enhanced ETO's pro-apoptotic effect by increasing caspase activities. The combination of Cur and ETO significantly reduced Bcl-2 gene expression while upregulating Bax expression. Furthermore, treatment with this combination elevated the protein levels of p53, p21, and Bax, compared to ETO or Cur alone, while significantly decreasing Bcl-2 protein levels.

Conclusions: Cur has the potential to amplify ETO-induced apoptosis in BC cells. This combination may offer a promising therapeutic approach for BC.