Exosome-Mediated Transfer of microRNAs Within the Tumor Microenvironment and Neuroblastoma Resistance to Chemotherapy

Background: How exosomic microRNAs (miRNAs) contribute to the development of drug resistance in the context of the tumor microenvironment has not been previously described in neuroblastoma (NBL). Methods: Coculture experiments were performed to assess exosomic transfer of miR-21 from NBL cells to human monocytes and miR-155 from human monocytes to NBL cells. Luciferase reporter assays were performed to assess miR-155 targeting of TERF1 in NBL cells. Tumor growth was measured in NBL xenografts treated with Cisplatin and peritumoral exosomic miR-155 (n = 6 mice per group) CD163, miR-155, and TERF1 levels were assessed in 20 NBL primary tissues by Human Exon Arrays and quantitative real-time polymerase chain reaction. Student's t test was used to evaluate the differences between treatment groups. All statistical tests were two-sided. Results: miR-21 mean fold change (f.c.) was 12.08+/-0.30 (P < .001) in human monocytes treated with NBL derived exosomes for 48 hours, and miR-155 mean f.c. was 4.51+/-0.25 (P < .001) in NBL cells cocultured with human monocytes for 48 hours. TERF1 mean luciferase activity in miR-155 transfected NBL cells normalized to scrambled was 0.36 +/- 0.05 (P <.001). Mean tumor volumes in Dotap-miR-155 compared with Dotap-scrambled were 322.80+/-120mm(3) and 76.00+/-39.3mm(3), P = .002 at day 24, respectively. Patients with high CD163 infiltrating NBLs had statistically significantly higher intratumoral levels of miR-155 (P = .04) and lower levels of TERF1 mRNA (P = .02). Conclusions: These data indicate a unique role of exosomic miR-21 and miR-155 in the cross-talk between NBL cells and human monocytes in the resistance to chemotherapy, through a novel exosomic miR-21/TLR8-NF-kappa B/exosomic miR-155/TERF1 signaling pathway.