Multiple endocrine neoplasia type 1 (MEN1) syndrome is caused by mutations in the MEN1 gene, resulting in reduced or completely absent production of the oncosuppressor menin. This genotype often results in the occurrence of tumors in endocrine tissues (parathyroids, pituitary gland, and endocrine pancreas) and beyond. However, although more than 1,500 MEN1 mutations have been identified, no genotype-phenotype relationship has been observed in this syndrome, suggesting that specific clinical phenotypes may be due to the action of other factors, such as epigenetics. Over the past 20 years, it has been seen that deregulation of microRNA (miRNA) expression may play a key role in the onset and progression of several diseases, including MEN1. Moreover, recently, in addition to their intracellular counterparts, a new class of extracellular, or circulating, miRNAs has been identified whose variation in expression levels seems to be associated with specific diseases, including cancers. In this review, we look at the miRNAs that might be involved in the pathogenesis of MEN1, and therefore represent possible targets for developing new therapies for the syndrome. In addition, we discuss the possibility of using some circulating miRNAs as potential future diagnostic and prognostic biomarkers of MEN1.
