KEAP1 and non-small cell lung carcinoma: In this study, we demonstrated for the first time that (I) miR-421 downregulates KEAP1 expression by targeting the KEAP1 3′UTR; (II) reduced KEAP1 confers drug resistance in NSCLC at least partly via miR-421 overexpression; and (III) miR-421 expression is upregulated by the Wnt/β-catenin signalling pathway.