Silencing of Exosomal miR-181a Reverses Pediatric Acute Lymphocytic Leukemia Cell Proliferation

Exosomes are cell-generated nano-vesicles found in most biological fluids. Major components of their cargo are lipids, proteins, RNA, DNA, and non-coding RNAs. The miRNAs carried within exosomes reveal real-time information regarding disease status in leukemia and other cancers, and therefore exosomes have been studied as novel biomarkers for cancer. We investigated the impact of exosomes on cell proliferation in pediatric acute lymphocytic leukemia (PALL) and its reversal by silencing of exo-miR-181a. We isolated exosomes from the serum of PALL patients (Exo-PALL) and conditioned medium of leukemic cell lines (Exo-CM). We found that Exo-PALL promotes cell proliferation in leukemic B cell lines by gene regulation. This exosome-induced cell proliferation is a precise event with the up-regulation of proliferative (PCNA, Ki-67) and pro-survival genes (MCL-1, and BCL2) and suppression of pro-apoptotic genes (BAD, BAX). Exo-PALL and Exo-CM both show over expression of miR-181a compared to healthy donor control exosomes (Exo-HD). Specific silencing of exosomal miR-181a using a miR-181a inhibitor confirms that miR-181a inhibitor treatment reverses Exo-PALL/Exo-CM-induced leukemic cell proliferation in vitro. Altogether, this study suggests that exosomal miR-181a inhibition can be a novel target for growth suppression in pediatric lymphatic leukemia.