Circulating MicroRNAs in Cancer
ABSTRACT MicroRNAs (miRNAs) are small (~22 nucleotide) non-protein-encoding RNAs that posttranscriptionally regulate gene expression
via suppression of specific target messenger RNAs. Aberrations in miRNA expression have been associated with cancer and numerous
other diseases. Recently, extracellular miRNAs have been found to be present in the circulation, where they exist in a stable,
ribonucleaseresistant form. Preliminary reports suggest that tumor-derived circulating miRNAs may serve as a new class of
blood-based biomarkers for cancer. Here, we describe early advances in the research field of circulating miRNA, review the
possibilities and challenges associated with the development of miRNAs as biomarkers for cancer and other disease states,
and discuss the possible biological roles of this newly discovered species of circulating nucleic acid.