Caffeic acid phenethyl ester reverses doxorubicin resistance in breast cancer cells via lipid metabolism regulation at least partly by suppressing the Akt/mTOR/SREBP1 pathway.

Chemotherapy is one of the common treatment methods for breast cancer, but chemoresistance is a severe challenge. Caffeic acid phenethyl ester (CAPE) is an active ingredient of propolis extract and has been shown to have a variety of beneficial effects, and its potential as a treatment for breast cancer is worth exploring. The effects of CAPE on doxorubicin (DOX) resistance were determined by cell counting kit-8 (CCK-8) assay, colony-formation assay, and flow cytometry. Oil Red O staining and the detection of free fatty acids, triglycerides, phospholipids, and cholesterol were performed to assess the status of lipid metabolism. Quantitative polymerase chain reaction (qPCR) and western blotting were applied to investigate the molecules involved in lipid metabolism and the protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/sterol regulatory element binding protein 1 (SREBP1) pathway. CAPE treatment reversed DOX resistance in breast cancer cells and suppressed their lipid metabolism. In addition, CAPE combined with DOX remarkably suppressed SREBP1 expression in part by inhibiting Akt/mTOR pathway activation. Furthermore, by inhibiting lipid metabolism, partly via the Akt/mTOR/SREBP1 pathway, CAPE ultimately reversed DOX resistance in breast cancer. Our results suggest that CAPE treatment reversed DOX resistance in breast cancer cells, at least in part by inhibiting Akt/mTOR/SREBP1 pathway-mediated lipid metabolism, indicating that CAPE may be an effective substance to assist in the treatment of breast cancer.