Abstract 3325: Intratumoral STING activation on artificially generated cutaneous metastasis of EML4-ALK lung cancer alters immunologic milieu of primary tumor
Authors: Synn Chun-Bong , Lee Ji Min , Lim SunMin , Kim Do Hee , Gheorghiu Bianca-Ioana , Kim Jae-Hwan , Lee Wongeun , Kim Sung-Eun , Park Sungwon , Ahn Beung-Chul , Jo Ha Ni , Hong Min Hee , Kim Hye Ryun , Pyo Kyoung-Ho , Cho Byung Chul 
Published: September 2020

Abstract
Introduction: Therapeutic monoclonal antibodies targeting immune checkpoints inhibitors (ICIs) are game changers in the treatment landscape of multiple solid tumors. However, response rate remains relatively low in most cases. Particularly, anti-PD-1 or PD-L1 therapies are not effective in EML4-ALK rearranged- and EGFR mutant-NSCLC patients due to their cold immune microenvironment. Recently, activation of stimulator of interferon genes (STING) has shown potential to enhance antitumor immunity through induction of various pro-inflammatory cytokines and chemokines. In this study, we attempted to induce inflamed tumor microenvironment by artificially generating skin metastasis using intratumoral STING activation in EML4-ALK transgenic mice.
Methods: EML4-ALK transgenic mice were implanted with a new EML4-ALK tumor subcutaneously. The size of lung primary tumor and subcutaneous tumor were each measured by micro-MRI and calipers, respectively. The treatment groups were divided into the control group, tumor-implanted group, and intratumor STING activation group (skin). On day 14, subcutaneous tumor, primary tumor (lung), and systemic immune organs were collected for further analysis.
Results: STING agonist promotes pIRF3 signaling and massive immune cell recruitment in skin region, the subcutaneous tumor was dramatically reduced with hyperinflammation. In addition, primary tumor (lung) was observed with increased T cell population in tumor with necrotic regions. IFN-gamma expression was increased in bronchoalveolar fluid in STING activation group compared to control and tumor only groups (P &lt; 0.05). Tumor macrophages and NK cells were increased compared to control group (P &lt; 0.05, P = ns, respectively). We considered that skin consists of cutaneous innate immune cells, especially, macrophage. Increased T cells and macrophages were observed in STING activated tumor within 6 hours. The in vitro assay proved that macrophages highly express chemokines (CCL5, CCL2, and CCL12) which is recruiting T cells and myeloid cells. This initial immune activation results in increased tumor-specific T cell, especially, memory helper T cell (CD3+CD4+CD44+) in spleen, LN and MLN. We tested anti-IFN-beta antibody for neutralization of STING activity in vivo. The IFN-gamma expression of lymphocytes in MLN was reduced but not significant.
Conclusion: This study confirmed that STING activation in cold tumor alters inflamed-immunologic milieu of primary tumor via hyper cutaneous immune activity with pivotal roles of macrophage. Our findings provide a rationale for further clinical investigations.
Keywords: STING, cutaneous metastasis, EML4-ALK
Citation Format: Chun-Bong Synn, Ji Min Lee, SunMin Lim, Do Hee Kim, Bianca-Ioana Gheorghiu, Jae-Hwan Kim, Wongeun Lee, Sung-Eun Kim, Sungwon Park, Beung-Chul Ahn, Ha Ni Jo, Min Hee Hong, Hye Ryun Kim, Kyoung-Ho Pyo, Byung Chul Cho. Intratumoral STING activation on artificially generated cutaneous metastasis of EML4-ALK lung cancer alters immunologic milieu of primary tumor [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 3325.