It has been shown that the promoter region of Keap1 gene is hypermethylated in many lines of cancer cells, such as colorectal cancer59 and lung cancer.60 This hypermethylation is responsible for inactivation of Keap1 function with the concomitant activation of Nrf2, which is associated with cancer development and drug resistance.61 Genistein, a natural isoflavone, inhibits the activity and the expression of DNMT1.62 Owing to this property genistein decreases DNA methylation in the promoter region of tumour suppressor genes,62 as well as in that of keap1 gene. This evidence concerns the gene DNMT1 and lung cancer.