Circulating micro ribonucleic acids (miRNAs): promising biomarkers for human lung and liver cancers

Micro ribonucleic acids (miRNA) is released and circulated in the blood of cancer patients. Changes in the levels of circulating nucleic acids have been associated with tumor burden and malignant progression. In the past decade, lots of information on the potential use of circulating nucleic acids for cancer screening, prognosis and monitoring of the efficacy of anticancer therapies has emerged. 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 July 2011, using 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 lung or liver cancers and studies published in the English literature. The current review showed that different researches used different measurement methods which might impact the results; Cancers treatment might have an effect 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 quantitative meta-analyses. In this review, based on those researches, circulating miRNAs are promising and difficulties for their future application for diagnosing human lung or liver cancers.   Key words:  MiRNAs, lung cancer, liver cancer, biomarker.