Generally, disease susceptibility is determined based on changes not only in DNA sequen‐ ces but also in the activities of genes and chromosomal regions. Epigenetic regulation has attracted attention as a mechanism underlying changes of activities of genes and chromoso‐ mal regions. Epigenetic modification regulates gene activity and is essential for cell division and histogenesis. Genetically, phenotype diversity of identical cells is thought to be caused by differences in epigenetic profiles. Epimutations have also recently been recognized as the first step of tumorigenesis of cancers and are thought to be direct dispositions to cancers [1].