Abstract 5076: Tumor cell-derived exosomes educate bone marrow mesenchymal stromal cells toward a protumorigenic function

Abstract

Abstract The bone marrow constitutes a microenvironment for tumor cells that promotes their survival, dormancy and therapeutic resistance. Central to this sanctuary function are mesenchymal stromal cells (MSC) which, like tumor-associated macrophages, can have an anti- or a pro-tumorigenic function in cancer progression. Here, using neuroblastoma, the second most common cancer in children that is highly metastatic to the bone marrow as a model of tumor cell - MSC communication - we have explored the mechanism by which tumor cells “educate” MSC toward a pro-tumorigenic function. We demonstrate that neuroblastoma cells release 30-100 nm size extracellular vesicles rich in tetraspanins (CD63) and chaperone proteins (HSP70), and therefore with characteristics of exosomes, and that they are captured by MSC. As a result, MSC increase their expression of several pro-tumorigenic cytokines and chemokines like interleukin (IL)-4, IL-6, IL-8, vascular endothelial cell growth factor (VEGF) and monocyte-chemotactic protein-1 (MCP-1). Capture of tumor-derived exosomes by MSC activates MEK/ERK1/2 and Akt (but not NF-κB), and whereas MEK/ERK1/2 activation is critical for the production of pro-tumorigenic cytokines/chemokines, Akt activation is not. In addition to the presence of structural, metabolic and chaperone proteins and the absence of inflammatory cytokines, a proteomic analysis of the cargo of these neuroblastoma-derived exosomes revealed an abundance of Galectin-3 binding protein (Gal-3BP), a protein that we had previously reported to increase the transcriptional expression of IL-6 in MSC. Further supporting the role of exosomes in educating MSC, we found that inhibition of exosome release in neuroblastoma cells by knock-down of Rab-27B, a GTPase involved in exosome secretion, was associated with a suppression of cytokine/chemokine production by MSC. We then demonstrated that “educated” MSC stimulate neuroblastoma cell proliferation both in vitro and in vivo and their resistance to chemotherapy in a signal transduction and activation (STAT)3 and MEK-ERK1/2- dependent manner. These data thus indicate that the production of exosomes by tumor cells induces the production of cytokines and chemokines in bone marrow-derived MSC, contributing to the protective microenvironment of the bone marrow niche. Citation Format: Rie Nakata, Lucia Borriello, Muller Fabbri, Hiroyuki Shimada, Yves A. Declerck. Tumor cell-derived exosomes educate bone marrow mesenchymal stromal cells toward a protumorigenic function. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5076. doi:10.1158/1538-7445.AM2015-5076