DICER1 and cancer: The currently known mechanisms responsible for changes in miRNA expression in cancer include genomic deletions or amplifications, chromosomal translocations, epigenetic silencing by DNA methylation, and impairments of the miRNA biogenesis pathway, such as the frameshift mutation of exportin-5 (Melo et al., 2010), the downregulation of Dicer (Karube et al., 2005; Merritt et al., 2008), and the frameshift mutation of TARBP2 (Melo et al., 2009).