Abstract 196: Antitumor activity of lenvatinib against acquired resistance tumor to anti-VEGF therapy in mouse syngeneic tumor models
Authors: Ichikawa Kenji , Miyano Saori Watanabe , Minoshima Yukinori , Matsui Junji , Funahashi Yasuhiro 
Published: August 2019

Abstract
Anti-vascular endothelial growth factor (VEGF) therapies have been in clinical use to treat patients with multiple types of cancers, but benefits of anti-VEGF therapy are still limited because of the acquired resistance to the treatment. In this study, we developed a novel resistance model to anti-VEGF therapy by expressing VEGFR2-Fc in mouse Renca and B16F10 tumor models. We investigated activated signaling pathways in established resistant tumors by differentially expressed gene analysis and using pathway analysis using Reactome based on RNA-Seq data. Differentially expressed gene analysis identified 293 genes, which are altered commonly in both resistant tumors, and pathway analysis showed that those genes were enriched in FGF2-FGFR2 signaling pathway. IHC analysis by staining with anti-CD31 and αSMA antibodies demonstrated that tumor vessels in VEGFR2-Fc expressing resistant tumors were covered with pericytes, and further IHC analysis with anti-FGF2 antibody indicated that FGF2 was stained in pericytes, which covered endothelial cells in VEGFR2-Fc expressing tumor. Moreover, we isolated CD31 positive cells as endothelial cells, CD90.2 positive cells as pericytes, and CD45 positive cells as tumor infiltrated lymphocytes, respectively. Expression level of Fgf2 and Fgfr2 mRNA in these subsets from Mock tumors and VEGFR2-Fc expressing tumors were analyzed. As a result, Fgf2 and Fgfr2 mRNA expressions in VEGFR2-Fc expressing tumors were upregulated in pericytes and endothelial cells, respectively compared with Mock tumors. These results suggested that there is a spatially effective activation of FGF signaling pathway between endothelial cells and pericytes in tumor vessels that are resistant to anti-VEGF therapy. Indeed, by expression of FGFR2-Fc, in vivo tumor growth of anti-VEGF therapy-resistant tumors was suppressed as well as angiogenesis. Lenvatinib mesilate (lenvatinib) is an oral multiple receptor tyrosine kinase (RTK) inhibitor that suppresses the kinase activities of VEGF receptors (VEGFR1-3), in addition to other proangiogenic and oncogenic pathway-related RTKs including fibroblast growth factor receptors (FGFR1-4), the platelet-derived growth factor receptor (PDGFR) α, KIT, and RET. Lenvatinib suppressed phosphorylation of FGFR2 in VEGFR2-Fc expressing tumors, and showed antitumor activity accompanied with further decrease of tumor vessels. But, sorafenib and aflibercept, which are selective inhibitors against VEGF signaling pathway, didn’t show antitumor activity against anti-VEGF therapy resistant tumors. In conclusion, our findings revealed key roles of pericytes expressing FGF2 in anti-VEGF therapy acquired resistant tumor models, where lenvatinib showed antitumor activity, indicating an importance of inhibition of FGF signaling pathway to suppress escape from anti-VEGF therapy.
Citation Format: Kenji Ichikawa, Saori Watanabe Miyano, Yukinori Minoshima, Junji Matsui, Yasuhiro Funahashi. Antitumor activity of lenvatinib against acquired resistance tumor to anti-VEGF therapy in mouse syngeneic tumor models [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 196.