Exosomal microRNAs as Potentially Useful Tools in Cancer Biomarker Discovery

The development of minimally invasive tests for the detection and monitoring of cancers could greatly reduce the worldwide health burden of cancer. Recent discovery of a new class of small (22mer) non-coding RNA (miRNAs) opened up new perspectives in biomarker research. Since miRNA are directly involved in the regulation of almost all key cellular processes, including development, differentiation, proliferation, cell death and metabolism, they may prove to be powerful cancer biomarkers. Unlike other types of biomarkers, miRNAs in the circulation are protected within lipoprotein vesicles and thus are remarkably stable, making them robust and reliable biomarkers of cancer. In this review, we provide an overview on circulating miRNAs and their great potential as highly specific and sensitive biomarkers for tumor classification and prognostication. We discuss exosomal origin of the circulating miRNAs and additionally, address some recent findings in the new and upcoming area of exosomal miRNAs from cell culture supernatant and their potential in biomarkers discovery. We also review a selected number of recent patents relevant to the area of exosomal miRNAs relevant to biomarker discovery.