Effect of Selected Phytochemicals and Apple Extracts on NF-κB Activation in Human Breast Cancer MCF-7 Cells

Nuclear factor κB (NF-κB) is a transcription factor, which plays an important role in inflammation, cell proliferation, apoptosis, and immunity in eukaryotes. In cancer cells, NF-κB induces resistance to anticancer chemotherapeutic agents by increasing cell proliferation and inhibiting apoptosis. Therefore, inhibition of NF-κB activation in cancer cells is advantageous in cancer therapy by lowing the resistance to chemotherapy. Several phytochemicals from fruits and vegetables have been reported to inhibit NF-κB activation, but the mechanisms of how the phytochemicals work have not been fully understood. The present study examines the effects of selected phytochemicals and apple extracts on TNF-α-induced NF-κB activation in human breast cancer MCF-7 cells. Apple extracts significantly inhibited the TNF-α-induced NF-κB activation at a dose of 5 mg/mL (p < 0.05). Curcumin also significantly blocked the TNF-α-induced NF-κB activation at doses of 10 and 20 μM (p < 0.05). Neither apple extracts nor curcumin affected phosphorylation of inhibitor of NF-κB-α (IκB-α); both significantly inhibited proteasomal activity of MCF-7 cells at doses of 2.5 and 5 mg/mL of apple extracts and 20 μM of curcumin (p < 0.05). These results suggest that apple extracts and curcumin have the capabilities of inhibiting TNF-α-induced NF-κB activation of MCF-7 cells by inhibiting the proteasomal activities instead of IκB kinase (IKK) activation. Keywords: Breast cancer; phytochemicals; curcumin; apples; MCF-7 cells