A549 cells are derived from an adenocarcinoma of human alveolar basal epithelium and exhibit aberrant activation of NRF2 owing to two mechanisms: one is a somatic mutation in Keap1 at G333C (Singh et al., 2006) and the other is the epigenetic silencing by methylation in the promoter of Keap1 (Wang et al., 2008). Here, KEAP1 is linked to adenocarcinoma.