17β-estradiol-induced ACSL4 protein expression promotes an invasive phenotype in estrogen receptor positive mammary carcinoma cells

Long chain acyl-CoA synthase-4 (ACSL4) expression has been associated with an aggressive phenotype in breast carcinoma cells, whereas its role in ER alpha-positive breast cancer has not been studied. ACSL4 prefers 20-carbon polyunsaturated fatty acid (PUFA) substrates, and along with other ACSLs has been associated with cellular uptake of exogenous fatty acids. 17 beta-estradiol induces proliferation and invasive capacities in ER alpha+ve breast carcinoma that is associated with modifications of cellular lipid metabolism. In this study, treatment of steroid-starved ER alpha-positive MCF-7 and T47D mammary carcinoma cells with 17 beta-estradiol resulted in increased cellular uptake of the PUFA arachidonic acid (AA) and eicosapentaenoic acid (EPA), important building blocks for cellular membranes, and increased ACSL4 protein levels. There was no change in the expression of the ACSL1, ACSL3 and ACSL6 protein isotypes. Increased ACSL4 protein expression was not accompanied by changes in ACSL4 mRNA expression, but was associated with a significant increase in the protein half-life compared to untreated cells. ER alpha silencing reversed the impact of 17 beta-estradiol on ACSL4 protein levels and half-life. Silencing of ACSL4 eliminated the 17 beta-estradiol-induced increase in AA and EPA uptake, as well as the 17 beta-estradiol-induced cell migration, proliferation and invasion capacities. ASCL4 silencing also prevented the 17 beta-estradiol induced increases in p-Akt and p-GSK3 beta, and decrease in E-cadherin expression, important events in epithelial to mesenchymal transition. Taken together, these results demonstrate that ACSL4 is a target of 17 beta-estradiol-stimulated ER alpha and is required for the cellular uptake of exogenous PUFA and the manifestation of a more malignant phenotype in ER alpha+ve breast carcinoma cells.