Abstract 199: TGF-β in exosomes facilitates HNSCC progression by accelerating tumor angiogenesis

Abstract TGF-β is a key regulator for tumor initiation and progression in head and neck squamous cell carcinoma (HNSCC). Tumor-derived exosomes (TEX) contain TGF-β and accumulate in the tumor microenvironment (TME). This study characterizes the TGF-β content of HNSCC-derived exosomes and evaluates in vitro and in vivo TGF-β signaling by exosomes that results in promotion of angiogenesis. TEX were isolated from supernantants of 5 different HNSCC cell lines by mini size exclusion chromatography (mini-SEC) and characterized by electron microscopy, nanoparticle tracking analysis and mass spectrometry (LC-MS/MS). TGF-β content in exosomes was evaluated by immunoblotting. Proliferation and migration of SVEC4-10 lymphendothelial cells in response to TEX were investigated in vitro and results were confirmed in vivo, using a matrigel plug model in mice. In these experiments a novel trivalent TGF-β receptor trap (mRER) was used to inhibit TGF-β signaling. TGF-β levels and activity were similarly measured in exosomes isolated from plasma of 20 HNSCC patients. TEX carried high levels of TGF-β and were found to be potent inducers of angiogenesis in vitro and in vivo through functional reprogramming and phenotypic modulation of endothelial cells. Proliferation (p<0.01) and migration (p<0.01) by SVEC4-10 were stimulated by TEX and effects were inhibited by mRER treatment of SVEC4-10 (p<0.05). TEX promoted formation of defined vascular structures in vivo, and increased (p<0.001) vascularization in matrigel plugs relative to control. Those effects were inhibited by mRER treatment (p<0.05). Exosomes in plasma of HNSCC patients carried varying levels of TGF-β, and patients with nodal metastases had elevated TGF-β levels (p<0.01) relative to patients with no meastasis.The data show that TGF-β signaling by TEX in HNSCC promotes angiogenesis and drives tumor progression. Future efforts should focus on silencing TEX, thereby adding new options to existing anti-angiogenic therapies. Citation Format: Nils Ludwig, Saigopalakrishna S. Yerneni, Cynthia S. Hinck, Monika Pietrowska, Andrew P. Hinck, Theresa L. Whiteside. TGF-β in exosomes facilitates HNSCC progression by accelerating tumor angiogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 199.