Abstract 3267: EGFR inhibition in EGFR-mutant lung cancer triggers the innate immune response associated with tumor immune escape
Authors: Shiiya Akihiko , Noguchi Takuro , Tomaru Utano , Ariga Shin , Takashima Yuta , Ohhara Yoshihito , Taguchi Jun , Takeuchi Satoshi , Shimizu Yasushi , Kinoshita Ichiro , Koizumi Tomonobu , Matsuno Yoshihiro , Shinagawa Naofumi , Sakakibara-Konishi Jun , Dosaka-Akita Hirotoshi 
Published: June 2023

Abstract
EGFR-tyrosine kinase inhibitors (TKIs) benefit patients with EGFR-mutant non-small cell lung cancer (NSCLC). Still, the majority of patients eventually develop resistance to the therapy. This study thus explored therapeutic targets to overcome this resistance immunologically. Our screening in the public database and in vitro confirmatory experiments revealed that the expression of the innate immune checkpoint CD24 was induced in EGFR-mutant NSCLC cell lines such as PC9 and H1975 when treated with EGFR-TKIs. Immunohistochemistry revealed tissue samples from patients who developed resistance to EGFR inhibition without the acquired T790M mutation demonstrated increased tumor CD24 expression compared to pre-treatment samples. Tumor CD24 binds to Siglec-10 on macrophages and inhibits tumor cell phagocytosis in breast and ovarian cancer. However, in NSCLC, we found that the transcriptional expression levels of SIGLEC-10 across human tumor-associated macrophages were quite heterogeneous, as evidenced by scRNA-seq. In addition, human monocyte-derived macrophages (MDMs) required M-CSF, IL-10, and TGF-β to express Siglec-10. Its expression was absent in MDMs differentiated either by GM-CSF±IFN-γ/LPS or M-CSF±IL-4. These data suggest that the CD24/Siglec-10 inhibitory pathway may be present but partial in NSCLC. Therefore, we asked whether CD24-targeted therapy could be beneficial regardless of the presence of the CD24/Siglec-10 inhibitory pathway. Using our MDM differentiation protocols mentioned above, MDMs devoid of Siglec-10 facilitated antibody-dependent cellular phagocytosis of EGFR-TKI-treated PC9 tumor cells when co-cultured with anti-CD24 monoclonal antibodies. Subsequently, we focused on cell-free DNA (cfDNA) released from dying tumor cells. The amounts of cfDNA from dying tumor cells were at least twice and more by EGFR-TKIs than conventional cytotoxic drugs such as paclitaxel. cfDNA from EGFR-mutant cells following EGFR inhibition activated the IRF pathway in THP-1 monocytes in a STING-dependent manner. Moreover, PMA-differentiated THP-1 monocytes no longer produced CXCL9 upon interferon-γ stimulation when pre-treated with cfDNA. The same results were obtained when they were pre-treated with interferon-α. In conclusion, we demonstrated two potential mechanisms which could facilitate tumor immune escape. Targeting these pathways may overcome the resistance to EGFR inhibition in patients with EGFR-mutant NSCLC.
Citation Format: Akihiko Shiiya, Takuro Noguchi, Utano Tomaru, Shin Ariga, Yuta Takashima, Yoshihito Ohhara, Jun Taguchi, Satoshi Takeuchi, Yasushi Shimizu, Ichiro Kinoshita, Tomonobu Koizumi, Yoshihiro Matsuno, Naofumi Shinagawa, Jun Sakakibara-Konishi, Hirotoshi Dosaka-Akita. EGFR inhibition in EGFR-mutant lung cancer triggers the innate immune response associated with tumor immune escape [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3267.