Synergistic Effects of Caffeine and Paclitaxel in Breast Cancer Cells: Mechanistic Insights Into NF-κB and Nrf2 Signaling.

Breast cancer remains one of the most prevalent malignancies among women. Recent studies have explored the potential of phytochemicals such as caffeine as chemosensitizing agents in enhancing the efficacy of standard chemotherapeutics like paclitaxel. This study aimed to investigate the cytotoxic, apoptotic, inflammatory, and oxidative stress-related effects of caffeine alone and in combination with paclitaxel in MCF-7 cells. Cells were treated with various concentrations of caffeine (1-100 mM), paclitaxel (0-350 µg/mL), and their combinations for 24, 48, and 72 h. Cell viability was assessed using the MTS assay, and IC₅₀ values were calculated. The expression levels of Bax, Bcl-2, NF-κB, and Nrf2 proteins were analyzed by Western blotting. Both caffeine and paclitaxel induced time- and dose-dependent reductions in MCF-7 cell viability. The combination treatment showed synergistic cytotoxicity, with significantly lower IC₅₀ values compared to single-agent treatments. Western blot analysis showed that both treatments boosted pro-apoptotic Bax and decreased anti-apoptotic Bcl-2, with slightly less effect in the combination group. NF-κB levels increased considerably in caffeine and paclitaxel groups, but were lower in the combination group compared to paclitaxel alone, suggesting a possible reduction in inflammatory signaling. Nrf2 expression increased significantly with caffeine, suggesting oxidative stress responses. In MCF-7 cells, caffeine enhanced paclitaxel's pro-apoptotic and cytotoxic actions and modified inflammation and oxidative stress pathways in a complicated, dose-dependent manner. Cytotoxicity was synergistic; however, apoptotic and stress indicators may be antagonistic. In clinical circumstances, caffeine may be an adjuvant in breast cancer treatment, however mechanistic and in vivo investigations are needed.