Serum exosomal microRNAs as novel biomarkers for multiple myeloma

: Accumulating studies have focused on circulating microRNAs, which might be potential biomarkers for different malignancies. The aim of this study was to investigate the potential of serum exosomal microRNAs to be novel serum biomarkers for smouldering myeloma (SMM) or even multiple myeloma (MM). The levels of serum exosomal microRNAs and serum circulating microRNAs were measured in healthy individuals and patients with SMM (n = 20) or MM (n = 20). Serum exosomal microRNAs and serum circulating microRNAs were extracted from serum, and the expression levels of selected microRNAs were quantified by real-time polymerase chain reaction (PCR). The levels of serum exosome-derived miR-20a-5p, miR-103a-3p, and miR-4505 were significantly different among patients with MM, patients with SMM, and healthy individuals, while there were differences in the levels of let-7c-5p, miR-185-5p, and miR-4741 in patients with MM relative to those in SMM patients or healthy controls. Additionally, a significant correlation was rarely found between the levels of serum and exosomal microRNAs. This study shows that serum exosomal microRNAs can be used independently as novel serum biomarkers for MM.