Association between hypomethylation of specific smoking-related CpG sites and lung cancer

DNA hypermethylation and hypomethylation have been reported to play important roles in carcinogenesis (1). However, lung cancer was not known to be related to DNA methylation until Fasanelli et al. first reported it (2). DNA methylation is not a rare process and is correlated with normal cell development, differentiation, and a number of key physiologic processes, such as genomic imprinting, X-chromosome inactivation, repression of repetitive elements, and aging (3). Therefore, DNA methylation is not associated with carcinogenesis, but with normal physiological processes.