Endocrine Abstracts

The discovery of microRNAs (miRNAs) as the endogenous mediators of RNA interference was a major event in contemporary biomedical research. miRNAs were shown to be involved in the regulation of gene expression affecting several basic physiological and pathological processes as parts of the epigenetic machinery. Differential expression of tissue miRNAs were described in several diseases including tumours. In tumours, up- and down-regulated miRNAs can be classified as oncogenes or tumour suppressors, and miRNAs were established as markers of malignancy and prognosis. Novel findings have shown that miRNAs are found in body fluids, as well. miRNAs can be released via passive route (necrosis, inflammation) or by active secretion either in membrane vesicles (exosomes, microvesicles) or in association with macromolecular complexes (Argonaute 2 protein, or high-density lipoprotein). The circulating miRNAs of the blood can be exploited as a form of liquid biopsy, where miRNAs deliver epigenetic gene expression information from various tissues. From a biological point of view, actively secreted miRNAs in exosomes could be the most interesting. There are several forms of endocrine tumours, where the preoperative diagnosis of malignancy is difficult, such as adrenal tumours. Our research group has been involved in several studies on tissue and circulating miRNA expression in adrenal tumours.Circulating miRNAs can be determined both from unfractionated whole plasm/serum or from extracellular vesicles. The miRNA yield of whole plasm is higher, but actively secreted miRNAs in exosomes could be more specific. In adrenocortical tumours, we could achieve high specificity and sensitivity of exosomal miR-483-5p for the diagnosis of malignancy. Polymerase chain reaction or next generation sequencing are the best for the analysis of plasma miRNAs. The choice of reference gene in PCR studies is a major debated issue. In the session, the theoretical basis, methodological issues and potential applications of this novel field will be discussed.