The most accepted therapeutic regimen for treating ER-alpha breast cancer is Tamoxifen. Yet over 30% of patients gain resistance. Recently, lipid metabolism has been rising as a new mode of cancer drug resistance. In order for a rapid growth, cancer cells show a strong avidity for lipid which they obtain by de novo lipogenesis or increasing the uptake of exogenous lipids. Lipid metabolism may confer drug resistance, but little is known about its association with endocrine resistance. Thus, we aimed to investigate the association of lipid metabolism in the context of tamoxifen resistance. First, fatty acid translocase and membrane-associated fatty acid binding protein, both of which are responsible for fatty acid uptake, were overexpressed in MCF7/TAMR-8 and T47D/TR-1, TR-2 cell lines. Also the mRNA level of fatty acid activating enzyme, long-chain fatty-acid-coenzyme A, were elevated as well. Next, through Oil-red-O staining and Nile red staining followed by FACS analysis, we examined whether tamoxifen-resistant cells actually increase fatty acid uptake. When supplemented with free fatty acids, tamoxifen-resistant cell lines showed higher efficiency in fatty acid uptake compared to the control cell lines. Subsequently when the amount of triglyceride accumulation was measured, more TG were present in resistant cells at the basal level and after free fatty acid treatment. Taken together, these results suggest lipid uptake by cancer cells may play a role in driving tamoxifen-resistance in breast cancer.

Citation Format: Sewon Hwang, Mi-Ock Lee. Cellular fatty acid uptake is enhanced in tamoxifen-resistant breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3610.