Endocrine Abstracts

MicroRNAs, the endogenous mediators of RNA interference have been shown to be helpful as markers of malignancy and prognosis in various neoplasms. The use of microRNAs as biomarkers has been greatly expanded with findings showing their secretion into body fluids (liquid biopsy). MicroRNAs are released both passively due to necrosis and inflammation, and actively in extracellular membrane vesicles (exosomes, microvesicles) or in macromolecular complexes. Circulating microRNA can be determined both from unfractionated plasma/serum samples or from extracellular vesicles.

The preoperative diagnosis of adrenocortical cancer (ACC) is difficult and relies mostly on imaging. The applicability of circulating microRNA for the differential diagnosis of benign and malignant adrenocortical tumours has been investigated in some studies. The most reliable circulating microRNA for the diagnosis of adrenocortical cancer appears to be miR-483-5p. Overexpressed miR-483-5p showed a specificity approaching 100 %, and sensitivity of almost 90 % for ACC diagnosis in different studies on both unfractionated serum and extracellular vesicles. However, miR-483-5p was not significantly different in ACC compared to adrenal myelolipoma. Other microRNAs, such as underexpressed miR-195 might be promising markers. Circulating microRNAs can be exploited for the follow-up of ACC that could be of major clinical relevance. The circulating microRNA expression profiles in cortisol-secreting and hormonally inactive adrenocortical tumours are also different. Circulating microRNA markers for the two major forms of primary aldosteronism (unilateral adenoma and bilateral adrenal hyperplasia) have also been identified. Circulating microRNAs are promising markers, but there are still major differences among the findings on circulating microRNA by different research groups and therefore uniform methodologies and larger cohorts are needed to reduce interassay variability and to increase their reliability.