Circulating miRNAs: promising biomarkers of human cancer

With the development of technologies to look at the expression levels of hundreds of miRNAs at a time and the clear role of miRNAs in cancers, groups began looking at miRNAs profiles of different cancers, especially the circulating miRNAs. We intended to make sure whether circulating miRNAs could be a promising biomarker of human cancers.

We comprehensively searched the Cochrane Library, Medline and EMbase from 1966 to Nov 2009 for the following terms: ("miRNA" or "microRNA") and ("tumor" or "carcinoma") and ("plasma*" or "serum" or "circulating"). Detailed information was extracted from studies that met the inclusion criteria: blood-based miRNAs in human cancers and studies published in the English literature.

The current review show that different researches use different measurement methods which might impact the results; Cancers treatment might have an affect on circulating miRNAs; some miRNAs are multi-faceted RNA; small sample size might produce selection bias. Furthermore, because of the lack of randomized controlled trials and the heterogeneous nature of the available data, no attempt was made to perform quantitativemeta-analyses.

In this review, based on those researches, circulating miRNAs are promising and difficulties for their future application for diagnosing human cancers.