Abstract 6637: Inhibition of FGFR signaling by lenvatinib activates tumor interferon gamma signaling pathway and potentiates antitumor activity of anti-PD-1 antibody
Authors: Adachi Yusuke , Kamiyama Hiroshi , Ichikawa Kenji , Ozawa Yoichi , Fukushima Sayo , Goda Satoshi , Yamaguchi Shogo , Matsuki Masahiro , Miyano Saori Watanabe , Yokoi Akira , Kato Yu , Funahashi Yasuhiro 
Published: September 2020

Abstract
Background: Lenvatinib mesilate (LEN) is an oral multiple receptor tyrosine kinase (RTK) inhibitor that selectively inhibits the kinase activity of VEGFR1-3, in addition to other proangiogenic and oncogenic pathway-related RTKs including FGFR1-4; PDGFRα; KIT; and RET. To improve the efficacy of immune checkpoint inhibitors (ICI), combination treatments of ICI plus anti-angiogenic inhibitors are currently under investigation. Lenvatinib plus pembrolizumab is approved for 2nd line treatment of advanced endometrial carcinoma that is not microsatellite instability-high or mismatch repair deficient in the US, and several Ph3 clinical trials with this combination are ongoing. Immunosuppressive roles of VEGF in tumor microenvironment have been well studied; however, immunomodulatory effects of FGFR signaling and the effect of FGFR inhibition on antitumor activity of anti-PD-1 antibody (PD-1 Ab) are still largely unknown. In this study, we investigated mechanism of action underlying the activity of LEN and PD-1 blockade in syngeneic mouse renal cell carcinoma (RCC) model. We also explored the relationship between FGFR signaling and interferon (IFN) γ signaling pathway in cancer cells, and examined whether LEN has an impact on IFNγ pathway by FGFR inhibition.
Methods: We examined antitumor activity of combination treatment of LEN at 10 mg/kg (po, qd) plus PD-1 Ab at 10 mg/kg (ip, twice weekly) and VEGF-selective inhibitor axitinib (Axi) at 10 mg/kg (po, bid) plus PD-1 Ab in the RAG (murine RCC cell) subcutaneous tumor model. Gene expression profile in tumor tissues or cultured cells was analyzed by qRT-PCR or RNA seq. FGFR and IFNγ signaling pathways and their downstream molecules in tumor tissues and cultured cells were analyzed by western blot (WB) and immunofluorescence (IF).
Results: In the RAG model, the combination of LEN and PD-1 Ab showed greater tumor response than each single treatment and Axi plus PD-1 Ab combination. In the tumors, WB analysis revealed LEN treatment increased STAT1 phosphorylation and PD-L1 expression and decreased the expression of SOCS1, a suppressor molecule of JAK-STAT signaling. Increased expression of PD-L1 was also observed in the tumors by IF analysis. WB and qRT-PCR analyses elucidated that activation of FGFR signaling pathway inhibited the induction of B2M, PD-L1 and CXCL10 expression in RAG cells and human cancer cell lines. Inhibition of FGFR by LEN treatment reactivated the IFNγ signaling pathway.
Conclusion: Dual inhibition of VEGFR and FGFR signaling by LEN may exert the greater antitumor activity via activation of IFNγ pathway compared with single inhibition of VEGFR signaling in combination with PD-1 Ab. These results provide one of unique mechanisms of antitumor activity of LEN as VEGFR and FGFR inhibitor in combination with PD-1 blockade in preclinical models.
Citation Format: Yusuke Adachi, Hiroshi Kamiyama, Kenji Ichikawa, Yoichi Ozawa, Sayo Fukushima, Satoshi Goda, Shogo Yamaguchi, Masahiro Matsuki, Saori Watanabe Miyano, Akira Yokoi, Yu Kato, Yasuhiro Funahashi. Inhibition of FGFR signaling by lenvatinib activates tumor interferon gamma signaling pathway and potentiates antitumor activity of anti-PD-1 antibody [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 6637.