Last update:
03-Aug-2013

MicroRNAs (miRNAs) are 21−23 nucleotide RNA molecules that act as regulators of gene expression in eukaryotic cells by binding in a non-coding region of their mRNA targets, specifically the 3' untranslated region (3'UTR). Through this mechanism miRNAs regulate the self-renewal, differentiation and division of cells, via post-translational gene silencing. They have a significant role in many cellular processes, including stem cell proliferation and apoptosis, and in several diseases, cancer being the most prominent example. MiRNAs regulate gene expression via two separate mechanisms, namely inhibition of translation and promotion of mRNA degradation. Although miRNAs are encoded by only 3% of human genes, they regulate approximately 30% of protein-coding genes, which illustrates not only their significance in various regulatory pathways, but also their potential for manipulation of cellular functions. In the context of cancer, miRNAs have been shown to act as both oncosuppressor molecules and oncogenes, inhibiting and inducing tumor development, respectively. In addition, an overall underexpression of miRNAs has been observed in several types of cancer tissue in comparison with the corresponding normal tissues. A possible therapeutic use of miRNAs could thus involve restoration of the aberrant expression levels of target-genes that are implicated in signaling pathways in cancer cells, particularly in the cancer stem cells that are primarily responsible for carcinogenesis and metastases. This article highlights the crucial role that miRNAs play in stem cell proliferation, apoptosis and differentiation and their potential contribution to cancer therapeutics.

Key words: Cancer stem cells, Cancer therapeutics, miRNAs, Stem cells.