For the luciferase reporter assay, HCT116 cells were seeded into a 24-well plate (62,500 cells per well) in a total volume of 0.5 ml/well of cell culture medium and cultured overnight. Cells were then transfected with FuGENE ® HD transfection reagent using a total of 0.5 g of plasmid DNA (transfection mixture per well: 0.05 g of promoter reporter plasmid, 0.45 g of expression plasmid(s), 1.25 l FuGENE ® HD transfection reagent and 25 l cell culture medium without FCS).
To measure luciferase activity, cells were collected at given time points after transfection by lysing in cell culture lysis reagent (Promega) and measured with the Luciferase Assay System (Promega) following the manufacturer's recommendations.
For Western blot analysis, cell lysates were centrifuged at 13,000 × g to remove cell debris. The protein content was determined with the Bradford method using the BioRad protein assay reagent (BioRad, Munich, Germany). Protein extracts were immediately used for Western blot analysis or stored at -20 • C.