Exosomal microRNA-1 and MYO15A as a target for therapy and diagnosis in renal cell carcinoma

Exosomes are 40–100 nm nano-sized extracellular vesicles and are receiving increasing attention as novel structures that participate in intracellular communication. We previously found that miRNA-1 (miR-1) functions as a tumor suppressor in renal cell carcinoma (RCC). In this study, we investigated the function of exosomal miR-1 and the possibility that the exosome constitutes a tumor maker in RCC. First, we established the method to collect exosomes from cell lysates and human serum by a spin column-based method. Next, we assessed exosomes using Nanosight nanoparticle tracking analysis and Western blot analysis with exosome marker CD63. We confirmed that exosomes labeled with PKH26 fused with recipient cells. Moreover, miR-1 expression was elevated in RCC cells treated with exosomes derived from miR-1-transfected cells. Functional analyses showed that exosomal miR-1 significantly inhibited cell proliferation, migration and invasion compared to control treatment. Our analyses with TCGA database of RCCs showed that miR-1 expression was significantly downregulated in clinical RCC samples compared to that in normal kidney samples, and patients with low miR-1 expression had poorer overall survival in comparison to patients with high expression. Furthermore, RNA sequence analyses showed that expression levels of several genes were altered by exposure to exosomal miR-1. The analyses with TCGA database indicated that high expression of MYO15A was associated with a poorer outcome in RCC. In addition, RT-qPCR analysis of exosomes from clinical patients’ sera showed that MYO15A was significantly upregulated in RCC patients compared to that in healthy controls. This study showed that treatment with exosomal miR-1 might be an effective approach to treating RCCs. In addition, exosomal MYO15A could be a diagnostic tumor marker in RCCs.