Description:
<jats:title>Abstract</jats:title>
<jats:p>Background: Anti-Programed cell death 1 (PD-1) antibodies such as nivolumab or pembrolizumab show promising treatment effects in smoking-related lung cancer. However, anti-PD-1 antibodies have very little effect on epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC). EGFR mutations are the most frequent oncogenic drivers in non-smoking related NSCLC. Therefore, we aimed to explore the mechanism underlying tumor immunoediting in a lung cancer mouse model harboring EGFR mutations.</jats:p>
<jats:p>Methods: We previously established two strains of transgenic lung cancer mouse (C57BL/6) harboring a mouse Egfr exon 19-deletion (mDEL) or a human EGFR L858R (hLR) mutation, driven by a surfactant protein (SP)-C promoter (Ohashi, Cancer Sci. 2008; Ohashi, Cancer Res. 2009). These mice developed EGFR-dependent multifocal lung adenocarcinomas from type II pneumocytes. We modified the two models by transplanting lung tumors subcutaneously into C57BL/6 (Ohashi, AACR. 2018). Evaluation of mice tumor lymphocyte profile was done through flow cytometry or immunohistochemistry (IHC). Effects of T cell depletion or anti-mouse PD-1 antibody (4H2) in vivo were also assessed. Comprehensive analysis of mRNA expression of immuno-checkpoint molecules in the tumors was performed using PanCancer Immune Profiling Panel (NanoString Technologies).</jats:p>
<jats:p>Results: CD4+ T cells and/or CD8+ T cells were depleted in the subcutaneously transplanted tumor model followed by treatment with gefitinib (50 mg/kg/day, 5 days/week) for 2 weeks. As a result, after gefitinib discontinuation, rapid regrowth was seen in the tumors from groups with depletion of CD8+ T cells; depletion of CD4+ T cells had little effect on tumor regrowth, and tumor inhibition continued for 2 weeks after cessation of gefitinib. IHC showed relatively increased numbers of CD4+ T cells in the mice tumors whereas a decrease in the number of CD8+ T cells or Foxp3 positive cells was noted. PD-L1 expression was not observed in the tumors. Consistently, 4H2 showed little effect on tumor growth in vivo. The cancer immune panel showed increased expression of immune mediators such as Ccl6, Clec4n, and Lcn2.</jats:p>
<jats:p>Conclusions: Our results suggest that CD8+ T cells can recognize mice tumors in vivo. New immuno-checkpoint molecules regulating CD8+ T cells from PanCancer Immune Profiling Panel were evaluated. Further, we plan to evaluate the efficacy of various immuno-checkpoint inhibitors in vivo.</jats:p>
<jats:p>Citation Format: Kazuya Nishii, Kadoaki Ohashi, Kiichiro Ninomiya, Go Makimoto, Hiromi Watanabe, Hirohisa Kano, Naofumi Hara, Heiichiro Udono, Katsuyuki Kiura. Tumor immunoediting in a lung cancer mouse model harboring EGFR mutations [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 582.</jats:p>