Abstract 1320: Hypoxic extracellular vesicles induce a pro-metastatic phenotype in neuroblastoma: from the delivery of miR-210-3p to the preconditioning of a metastatic niche
Authors: Fietta Anna , Fusco Pina , Germano Giuseppe , Cimetta Elisa 
Published: April 2023

Abstract
Neuroblastoma (NB) is a pediatric tumor of neural crest origin accounting for 7% of cancers and 15% of cancer deaths. Solid malignant tumors commonly contain hypoxic areas that stimulate release of extracellular vesicles (EVs), lipid bound vesicles secreted by cells into the extracellular space. In our study we demonstrated that EVs from hypoxic NB cells promote pro-metastatic features in vitro and in an in vivo zebrafish model. We characterized the microRNA cargo of EVs from NB cells and compared their expression in hypoxia vs. normoxia, finding that miR-210-3p was the most upregulated. By using both in vivo and in vitro models we demonstrated that EVs released by hypoxic NB cells induced changes that favor a malignant phenotype in normoxic NB cells by transferring miR-210-3p. We showed that EVs isolated from cells transfected with miR-210-3p-mimic and cultured in normoxic condition, increased the migration ability and invasiveness of NB cells like EVs from hypoxic NB cells. Cells treated with EVs isolated from cells transfected with miR-210-3p-inhibitor and cultured in hypoxic condition were unable to stimulate migration and invasion as efficiently as EVs derived from control transfected cells, despite cells were cultured in hypoxic conditions. We then focused on the effects of EVs in metastatic niches formation in vivo. Intravascular injection within the zebrafish embryo allows a non-invasive visualization of EVs dispersion, uptake, and interactions with host cells. We first demonstrated that EVs released under hypoxic conditions promote angiogenesis and are more easily internalized by endothelial cells than those purified from normoxic cells. Furthermore, we proved via microscopy imaging and cell sorting that the group injected with hypoxic EVs had higher numbers of macrophages. We then focused on the region of the embryo called caudal hematopoietic tissue (CHT) as a potential metastatic site. After EVs injection, we evaluated through qPCR the expression of mmp9, required for HSPC (hematopoietic stem and progenitor cells) egress from the CHT, and cxcl8 that enhances HSPC colonization in the CHT. Results highlighted that the expression of these genes increased after hypoxic EVs injection. We showed that hypoxic EVs induce i. angiogenesis in vivo, required for tumor and metastasis growth, and ii. increased number of macrophages, a major contributor to the tumor microenvironment which produce growth factors and chemokines promoting tumor angiogenesis. Our data demonstrate that hypoxic EVs can modify the behavior of recipient cells in the CHT, as a potential metastatic site, to prepare a ‘fertile soil’ for cancer cells colonization. In conclusion, our findings suggest that EVs released by hypoxic NB cells induce changes that favor a malignant phenotype in normoxic NB cells by transferring miR-210-3p both in vitro and in vivo.
Citation Format: Anna Fietta, Pina Fusco, Giuseppe Germano, Elisa Cimetta. Hypoxic extracellular vesicles induce a pro-metastatic phenotype in neuroblastoma: from the delivery of miR-210-3p to the preconditioning of a metastatic niche [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1320.