MicroRNAs (miRNAs) comprise species of short noncoding RNA that regulate gene expression post-transcriptionally. Recent studies have demon-strated that epigenetic mechanisms, including DNA methylation and his-tone modification, not only regulate the expression of protein-encoding genes, but also miRNAs, such as let-7a, miR-9, miR-34a, miR-124, miR-137, miR-148 and miR-203.