To test the hypothesis that SIM2 negatively regulates NFκB/p65-mediated transcription in breast cancer cells, we co-transfected a reporter plasmid encoding a NFκB binding site upstream of the luciferase gene (5x NFκB-luc) with the p65 subunit along with SIM2s in MCF7 cells and measured relative light units as a readout for NFκB activity. Here, NFKB1 is linked to breast carcinoma.