In order to evaluate the role of cholesterol and its biosynthetic precursor mevalonate in breast cancer progression, and since the goal of our work was to evaluate whether high cholesterol levels were responsible for greater tumor aggressiveness and resistance phenomena, we supplemented already cholesterol-containing media (10% FBS medium) with the indicated amounts of cholesterol and mevalonate, focusing our attention on the ability of the two metabolites to activate the ERRα pathway in four different breast cancer cell lines. The gene discussed is ESRRA; the disease is neoplasm.