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 cellswith epithelial-mesenchymal transition (EMT) features was investigated.
Methods: The breast cancer cell lineMCF-7-MEK5 with stably occurring EMT and tumour necrosis factor-α (TNF-α) tolerance was used as theexperimental model, whereas MCF-7 acted as the control. Tumour cells were implanted into nude mice for invivo analysis, and cerulenin was used as a FASN inhibitor. RT-PCR, real-time quantitative PCR and Westernblot were employed to detect the expression of FASN, TNFR-1, TNFR-2, Wnt-1, β-catenin and cytC at theRNA and protein levels.
Results: Compared with MCF-7, TNFR-1 expression in MCF-7-MEK5 was slightlychanged, TNFR-2 was decreased, and FASN, Wnt-1, β-catenin and cytC were increased. The expression ofWnt-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 followingmechanisms: FASN downregulated TNFR-2 expression through lipid rafts to make the cells less sensitive toTNF-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.