Abstract 6331: Cloaking VEGF in small extracellular vesicles as a cause of adaptive resistance to anti-VEGF therapy

Abstract

Abstract Despite the wide use of anti-vascular endothelial growth factor (VEGF) therapy (AVT) for many solid cancers, most of them become resistant to such therapy, resulting in progressive disease. Therefore, new biomarkers and strategies for blocking adaptive resistance of cancer to AVT are needed. Small extracellular vesicles (small EVs, with a size of <200 nm) have been extensively studied as crucial intercellular messengers by delivering DNA, RNA, and proteins to recipient cells. We hypothesized that the packaging of angiogenic factors, especially VEGF, into small EVs could cause adaptive resistance to AVT by evading recognition by therapeutic antiboides. In this study, we carried out a series of in vitro (immunoblot analysis, flow cytometry, tube formation, and immunofluorescence staining) and in vivo (subcutaneous mouse models and Matrigel plug angiogenesis assay) experiments to determine the roles of small EVs in AVT resistance. We found that cancer-derived small EVs increasingly package VEGF and other factors in response to AVT. Further studies showed that bevacizumab cannot recognize the VEGF packaged inside small EVs (eVEGF) and eVEGF was protected from being neutralized by bevacizumab. Notably, eVEGF was transferred to endothelial cells, triggered intracrine signaling, and subsequently increased the number of tubes formed in an in vitro angiogenesis assay. In addition, VEGF was present at higher levels in serum small EVs in mouse models of adaptive resistance of ovarian cancer to bevacizumab than in models of sensitivity to it. Ovarian cancer cell-derived eVEGF increased tumor growth despite treatment with bevacizumab. Collectively, our data provide a new mechanism whereby eVEGF evades recognition by therapeutic antibodies and promotes tumor angiogenesis and progression. These findings have implications for biomarkers and new therapeutic strategies for ovarian cancer therapy. Citation Format: Shaolin Ma, Lingegowda S. Mangala, Wen Hu, Emine Bayaktar, Wei Hu, Nicholas B. Jennings, Robert L. Coleman, Gabriel Lopez-Berestein, Anil K. Sood. Cloaking VEGF in small extracellular vesicles as a cause of adaptive resistance to anti-VEGF therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6331.