miR-34: From bench to bedside

The mir-34 family was originally cloned and characterized in 2007 as a p53 target gene. Almost immediately it became clear that its major role is as a master regulator of tumor suppression. Indeed, when overexpressed, it directly and indirectly represses several oncogenes, resulting in an increase of cancer cell death (including cancer stem cells), and in an inhibition of metastasis. Moreover, its expression is deregulated in several human cancers. In 2013, a miR-34 mimic has become the first microRNA to reach phase 1 clinical trials. Here we review the miR-34 family and their role in tumor biology, and discuss the potential therapeutic applications of miR-34a mimic.