[Circulating miRNAs as a new class of biomedical markers].

Search for new biomarkers able to improve patient diagnosis has become a real challenge in the era of personalized medicine. Considering that early detection of cancer greatly increases the chances for successful treatment, the identification of accurate biomarkers is essential. In addition, the possibility to optimize patients' care and follow-up using "companion" diagnostic tests is emerging under the term of theranostics and should become a key step in future therapeutics. Since their discovery in serum and their close associations with pathological conditions, miRNA found in biological fluids represent a new promising class of potential biomarkers. First identified in cancer patients, possible applications are very broad and address the vast majority of human diseases. This review focuses on recent advances in our knowledge of circulating miRNA. Their production in cells, export in extra-cellular environment and presumed physiological functions are addressed. The review also emphasizes their potential applications in clinics as biomarkers or therapeutic agents.