A role for the cancer-associated miR-106b similar to 25 cluster in neuronal stem cells

In the last decade, micro-RNAs (miRNAs) have emerged as major regulators of cell fate. They are involved in fine-tuning gene expression in normal developing tissues and are often aberrantly expressed in different disease states, including cancer. miRNAs are 20-25 nucleotide non-coding RNAs that repress the translation and stability of a large number of target mRNAs. The study by Brett et al in the previous issue of AGING adds to our understanding of how miRNAs regulate the differentiation of adult neural stem cells (NSCs) [1]. The authors used primary cultures of neural stem/progenitor cells (NSPCs) isolated from adult mice to investigate the importance of a specific miRNA cluster, miR-106b~25, in regulating the proliferative potential and differentiation of NSCs. This miRNA cluster is located within an intronic region of the Mcm7 gene and codes for three different miRNA species, miR-106b, miR-93 and miR-25. Interestingly, activation of this miRNA cluster has been observed in different tumour types and is involved in the inhibition of anti-proliferative and pro-apoptotic genes, such as p21, Bim and TGF-beta [2,3]. Furthermore, this cluster is overexpressed in prostate cancer where it is involved in the downregulation of PTEN expression and also cooperates with its host gene Mcm7 to drive tumourigenesis [4]