ESRRB and breast cancer: To confirm that elevated Cullin1 NEDDylation downregulates ERRβ expression in breast cancer, we treated different breast cancer cell lines (MCF7, T47D and MDA-MB-231) with varying concentrations of MLN4924 (0, 0.1, 0.3, 0.5 and 1.0 μM) for 48 h and determined the expression of ERRβ by western blotting.