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

Exosomes are cell-generated nano-vesicles (30-150 nm) found in most biological fluids. Major components of their cargo are lipids, proteins, RNA, DNA, and non-coding RNAs. Exosomes carry the fingerprint of the parental tumor and as such, may regulate tumor growth, progression and metastasis. We investigated the impact of exosomes on cell proliferation in pediatric acute lymphocytic leukemia and its reversal by silencing of exo-miR-181a. We isolated exosomes from serum of acute lymphocytic leukemia pediatric patients (Exo-PALL) and conditioned medium of leukemic cell lines (Exo-CM) by ultracentrifugation. Gene expression was carried out by q-PCR. We found that Exo-PALL promote cell proliferation in leukemic B cell lines as well as in the control B cell line. This exosome-induced cell proliferation is a precise event with 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 controls (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.