ABSTRACT
Over the past decade, small ribonucleic acids (RNAs), including microRNA (miRNA) and small interfering RNA (siRNA), have been demonstrated as specifi c regulators for gene expression (Kennedy 2002). Due to the big impact of small RNAs, the 2006 Nobel Prize was awarded to two scientists, Andrew Fire and Craig Mello. miRNA is a small noncoding regulatory RNA molecule ranging in size from 17 to 25 nucleotides, which was fi rst discovered in worms in 1993 (Lee et al. 1993), and observed in a number of animals, plants, and viruses several years later (Reinhart et al. 2000). To date, it has been found that a number of miRNAs were implicated and miRNA expression was deregulated in cancer. However, the mechanism of why and how miRNA becomes deregulated remains uncertain. As cancer is a complex genetic disease caused by the accumulation of mutations, leading to deregulation of gene expression and uncontrolled cell proliferation, the cancer-associated miRNAs, as effective cancer biomarkers, are attracting more and more attention for diagnosis and prognosis.
