Abstract 1374: Targeting lipid-laden macrophage efferocytosis enhances immune response to EGFR-tyrosine kinase inhibitor in EGFR-mutant lung cancer
Authors: Sook-Hee Hong, Nahyeon Kang, Okran Kim, Juyeon Park, Soon Auck Hong
Journal: Cancer Research (2025)

Abstract During macrophage phagocytosis, efferocytosis is the process of removing senescent or apoptotic cells and, unlike phagocytosis, induces anti-inflammation, angiogenesis, and wound repair. Inhibition of efferocytosis, one of the macrophage responses to apoptosis induced by EGFR-TKIs, may enhance their immunologic effects. We analyzed early immune microenvironment changes following osimertinib treatment in an human EGFR L858R genetically engineered mouse model, focusing on the effect of tumor-associated macrophage (TAM) efferocytosis signals on the immune microenvironment in response to osimertinib-induced tumor cell apoptosis. Methods: Doxycycline-induced transgenic mice (human EGFRL858R) were maintained with doxycyclin-impregnated food pellets to activate rtTA protein phosphorylation. Tumor progression and treatment response were monitored by MRI. Lung tumor development was confirmed, and mouse immune cells were isolated by CD45 MACS for single-cell RNA sequencing. Immediate immune profile changes after osimertinib or osimertinib and MERTK inhibitor (LDC1267) treatment were analyzed (days 1, 5, 15). All animal experiments were approved by the Institutional Animal Care and Use Committee of the Catholic University of Korea. Results: Six macrophage clusters were identified from scRNA-seq of the human EGFR-mutated lung cancer transgenic mouse model. These were categorized as antigen-presenting, alveolar, IFN-responsive, proliferative, and lipid-containing macrophages, with the latter further divided into cluster 2 (Lepr, Dapk1, MerTK, Olr1, Adarb1) and cluster 4 (FSTL1, Fabp5, Gpnmb, S100a1). Osimertinib treatment increased the proportion of cluster 2 from 8.9% to 13.4%. The top GO terms enriched in cluster 2 included response to oxidative stress, wound healing, immune response activation, tissue remodeling, and response to hypoxia, which demonstrated activated efferocytosis. In vitro macrophage co-culture models showed MerTK-mediated efferocytosis occurring 24 hours post-osimertinib treatment, MerTK inhibition of macrophage significantly decreasing CD206 expression and increasing pSTAT3 in U937 macrophages. Osimertinib and LDC1267 (MERTK inhibitor) combination treatment in the human EGFR mutant lung cancer mouse model increased pSTING expression in macrophages and inducing type 1 IFN response. The combination also enhanced CD8 T cell activation, evidenced by increased IFN-γ, TNF-α, granzyme, and CD25 expression compared to osimertinib alone (days 5 and 15). No change was observed in the CD44+/CD62L-/CD8 T cell population. Conclusions: EGFR-TKI-induced tumor cell death stimulated macrophage efferocytosis. Inhibiting macrophage efferocytosis can increase the type 1 IFN response, potentially inducing of starting immunogenic cell death. Citation Format: Sook-Hee Hong, Nahyeon Kang, Okran Kim, Juyeon Park, Soon Auck Hong. Targeting lipid-laden macrophage efferocytosis enhances immune response to EGFR-tyrosine kinase inhibitor in EGFR-mutant lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1374.