Let-7 downregulation has been observed in other types of cancer associated with reduced copy numbers, such as melanoma [47], with an upregulation of LIN28A/LIN28B, which is an RNA binding protein that inhibits Drosha or Dicer binding during let-7 biogenesis (breast cancer) [48], and with DNA hypermethylation (epithelial ovarian cancer) [49]. This evidence concerns the gene DICER1 and breast cancer.