Cell proliferation assay

Cell proliferation was analyzed using an MTT assay (Sigma-Aldrich; Merck KGaA, Darmstadt, Germany). The cells were seeded at a density of 5×10³ cells per well into 96-well plates overnight. Following the transfection of cells with siRARα and siCtrl, 20 µl MTT (5 mg/ml) was added to each well, and the cells were cultured for a further 4 h at 37°C. Then the formazan crystals formed were dissolved in DMSO. The absorbance was measured at 490 nm using an ELISA microplate reader. All experiments were performed in triplicate.