Abstract 6868: Exploring myeloid landscapes according to EGFR mutated NSCLC tumor microenvironment

Abstract Introduction: Although the use of immune checkpoint inhibitors (ICIs) has improved the survival rate of some patients, EGFR mutant (MT) NSCLC patients exhibit a poor response to ICIs compared to EGFR wild-type (WT) patients. It has been demonstrated that EGFR MT NSCLC cells contribute to immunosuppressive tumor microenvironments (TMEs) by secreting inhibitory cytokines and metabolites and recruiting pro-tumor immunogenic cells, thereby diminishing ICI efficacy. In particular, myeloid cells represent a major component of the TME and are involved in regulating tumor progression and metastasis, indicating anti- and pro-inflammatory heterogeneous functions. While single-cell based analyses have been conducted in various cell types, studies on the diversity of myeloid cells between EGFR WT and EGFR MT NSCLCs are insufficient. Therefore, we explored to reveal the presence of multifaceted myeloid cell populations and to modulate its functions to augment ICI response in NSCLC patients with EGFR MT using single-cell RNA analysis. Methods: Using the 10x Genomics Chromium system, we have generated single-cell RNA expression of a total of 904,174 cells from primary lung tissues of 95 patients with EGFR-WT (n=35), EGFR-MT TKI naïve (n=55), TKI post (n=5) and matched normal (n=22). Nine distinct cell lineages were annotated with canonical marker gene expression, focusing particularly on the myeloid (n=212,673 cells). Results: We characterized 22 transcriptional states of myeloid cells: 4 clusters of alveolar macrophages (AMs; PPARG+), 4 clusters of interstitial macrophages (IMs; SPP1+, FOLR2+, CCL2+), 4 clusters of conventional DCs (cDCs; CLEC9A+, CD1C+, LAMP3+), 2 clusters of mast cells (KIT+), 1 cluster of plasmacytoid DCs (pDCs; LILRA4+), proliferating cells (MKI67+), monocytes (FCN1+), neutrophil like cells (CSF3R+) and 4 other unidentified clusters. In tumor tissues, IMs constituted a significantly higher proportion compared to normal tissues (p<0.001), with EGFR-WT and EGFR-MT IMs exhibiting distinct characteristics. EGFR-WT IMs had a high proportion of cluster expressing FOLR2, a marker of tissue resident macrophages associated with CD8 T cell infiltration and activation. On the other hand, a major component of IMs from EGFR-MT was a cluster expressing SPP1 and its regulator MIF. SPP1 is well known to be involved in cancer cell progression, epithelial-mesenchymal transition, autophagy, and epigenetic alterations. The abundance of SPP1 IMs in the EGFR-MT TME refers to the formation of an immunosuppressive TME, potentially compromising the effectiveness of ICIs. Conclusions: We found that EGFR-MT TME comprised a high proportion of immunosuppressive IM cluster expressing SPP1, implying that it contributes to an immunosuppressive TME. Our findings suggest the possibility of developing strategies to enhance ICI responses by targeting SPP1-induced immunosuppressive TME in EGFR-mutant NSCLC patients. Citation Format: Eun Ji Lee, Juwon Ahn, You Won Lee, Minyeop Kim, Seung Yeon Oh, Yong Joon Park, Su-Jin Choi, JuHyeon Lee, Kyumin Lim, Kyoung-Ho Pyo, Jae Hwan Kim, Jii Bum Lee, Min Hee Hong, Sun Min Lim, Mi Ran Yun, Byoung Chul Cho. Exploring myeloid landscapes according to EGFR mutated NSCLC tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6868.