Moreover, since aberrant methylation is reversible through epigenetic drugs, treatment of lung cancer cell lines, including lung carcinoid, small cell lung cancer (SCLC), and adenosquamous carcinoma (ASC), with the DNA methylation inhibitor 5′-aza-2′-deoxycytidine (decitabine; DAC) can restore KEAP1 expression by demethylating its promoter P1 region. This evidence concerns the gene KEAP1 and lung cancer.