This decrease in PPEIP epimutation susceptibility (OEDR = log2 -1.25) in lung tumours suggests that DNA methylation is more tightly controlled in lung tumorigenesis and likely reduces the role DNA methylation plays in highly mutable signalling pathways such as PI3K-AKT, JAK/STAT and MAPK (Fig. 2) in lung cancers as compared to other tissues. This evidence concerns the gene AKT1 and lung cancer.