Intact miRNAs can be isolated from the circulation in significant quantities despite the presence of extremely high levels of RNase activity. The remarkable stability of circulating miRNAs makes them excellent candidates for biomarkers in diagnostic applications as well as therapeutic targets in a variety of disease states including melanoma. Circulating RNA molecules are resistant to degradation by RNases because they are encapsulated in membrane-bound microvesicles. We describe a convenient method for the use of ExoQuick, a proprietary resin developed by Systems Biosciences (Mountain View, CA), whereby microvesicles can be purified under gentle conditions using readily available laboratory equipment. This protocol allows for isolation all microvesicles, regardless of their origin, and provides a convenient method for identifying potential cancer-specific biomarkers from biological fluids including serum and plasma.
