Abstract 1807: Exosomal NM23 facilitates pro-angiogenic communication between triple-negative breast cancer cells and their vascular targets

Abstract Functional interactions between primary tumor cells and their vascular targets orchestrate the formation of a metastatic milieu enriched with oxygen and metabolic substrates. These interactions have been largely attributed to the activation of VEGF receptor pathways through localized tumor-mediated release of VEGF, in addition to indirect receptor phosphorylation. However, pro-angiogenic events are known to occur in the absence of VEGF and alternative pathways resulting in dual activation of neovascularization and enhanced vascular permeability are of growing interest. Our lab has previously shown that triple-negative human breast cancer (MDA-MB-231) cells elaborate exosomes carrying NM23, a nucleoside diphosphate kinase (eNDPK) that is suggested to act as an upstream mediator of vasodilation and pro-angiogenic activity through its action of elevating extracellular ADP/ATP levels. To further elucidate the role of eNDPK in breast cancer signaling and metastasis, we show that 231-exosomes induce a pro-angiogenic phenotype in both human umbilical vein and murine pulmonary endothelial cells. Treatment with an NDPK-specific inhibitor and an antagonist to the ADP/ATP-activated P2Y1 receptor results in amelioration of pro-angiogenic characteristics. Further, we report the development and application of a novel murine implant model to demonstrate increased specificity of 231 exosome targeting to pulmonary endothelial cells over unrelated cell lines. These results suggest the involvement of exosomes and eNDPK in pro-angiogenic communication between metastatic breast cancer cells and their vascular targets. Exosomes elaborated by these cells specifically target pulmonary endothelium in vivo, mirroring the organotropic nature of breast cancer metastasis. Implication of eNDPK in angiogenesis and metastasis may challenge current and invasive treatment methods in favor of developing novel small molecule inhibitors of eNDPK signaling. Lastly, eNDPK can be explored as a potential biomarker for early detection of metastatic breast cancer as it uniquely appears in the serum of patients with breast cancer and not in the serum of individuals with unrelated pathologies. Citation Format: Suzann Duan, Senny Nordmeier, Iain L. Buxton. Exosomal NM23 facilitates pro-angiogenic communication between triple-negative breast cancer cells and their vascular targets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1807. doi:10.1158/1538-7445.AM2017-1807