Besides known genetic aberrations, epigenetic alterations have emerged as common 
hallmarks of many cancer types, including lung cancer. Epigenetics is a process 
involved in gene regulation, mediated via DNA methylation, histone modification, 
chromatin remodeling, and functional noncoding RNAs, which influences the 
accessibility of the underlying DNA to transcriptional regulatory factors that 
activate or repress expression. Studies have shown that epigenetic dysregulation 
is associated with multiple steps during carcinogenesis. Since epigenetic 
therapy is now in clinical use in hematopoietic diseases and undergoing trials 
for lung cancer, a better understanding of epigenetic abnormalities is desired. 
Recent technologies for high-throughput genome-wide analyses for epigenetic 
modifications are promising and potent tools for understanding the global 
dysregulation of cancer epigenetics. In this chapter, studies of epigenetic 
abnormality and its clinical implication in lung cancers are discussed.