Mechanism of fatty acid synthase in drug tolerance related to epithelial-mesenchymal transition of breast cancer.

OBJECTIVE The mechanism of action of fatty acid synthase (FASN) in drug tolerance of breast cancer cells with epithelial-mesenchymal transition (EMT) features was investigated. METHODS The breast cancer cell line MCF-7-MEK5 with stably occurring EMT and tumour necrosis factor-α (TNF-α) tolerance was used as the experimental model, whereas MCF-7 acted as the control. Tumour cells were implanted into nude mice for in vivo analysis, and cerulenin was used as a FASN inhibitor. RT-PCR, real-time quantitative PCR and Western blot were employed to detect the expression of FASN, TNFR-1, TNFR-2, Wnt-1, β-catenin and cytC at the RNA and protein levels. RESULTS Compared with MCF-7, TNFR-1 expression in MCF-7-MEK5 was slightly changed, TNFR-2 was decreased, and FASN, Wnt-1, β-catenin and cytC were increased. The expression of Wnt-1 and β-catenin in MCF-7-MEK5 decreased after cerulenin treatment, whereas cytC expression increased. CONCLUSIONS The important function of FASN in the drug tolerance of breast cancer may be due to the following mechanisms: FASN downregulated TNFR-2 expression through lipid rafts to make the cells less sensitive to TNF-α, and simultaneously activated the Wnt-1/β-catenin signalling pathway. Thus, cytC expression increased, which provided cells with anti-apoptotic capacity and induced drug tolerance.