The siRNA sequence targeting NRF2 corresponds to the coding region nucleotides 1903–1921 (5′-GTAAGAAGCCAGATGTTAA-3′) in the NRF2 cDNA. The NRF2 siRNA duplex with the following sense and antisense sequences was used: 5′-GUAAGAAGCCAGAUGUUAAdUdU-3′ (sense) and 3′-dUdUCAUUCUUCGGUCUACAATT-5′ (antisense). KEAP1 siRNA corresponds to the coding region nucleotides 1545–1563 (5′-GGGCGTGGCTGTCCTCAAT-3′) in KEAP1 transcript variant 2. The KEAP1 siRNA duplex with the following sense and antisense sequences was used: 5′-GGGCGUGGCUGUCCUCAAUdUdU-3′ (sense) and 3′-dUdUCCCGCACCGACAGGAGUUA-5′ (antisense). To confirm the specificity of the inhibition, the siCONTROL non-targeting siRNA 1 (NS siRNA; 5′-UAGCGACUAAACACAUCAAUU-3′) with microarray-defined signature was used as a negative control. All of the siRNA duplexes were synthesized by Dharmacon Research (Lafayette, Colorado, United States). Cells in the exponential growth phase were plated at a density of 0.2 × 10⁶ cells/ml, grown for 12 h, and transfected twice at an interval of 48 h with 50 nM siRNA duplexes using Lipofectamine 2000 and OPTI-MEM reduced serum medium (Invitrogen) according to the manufacturer's recommendations. Concentrations of siRNAs were chosen on the basis of dose–response studies (data not shown).