Abstract 6278: Reprogramming of the tumor microenvironment via lipid-associated macrophage subtypes after neoadjuvant osimertinib treatment in <i>EGFR</i>-mutantnon-small cell lung cancer

Abstract Introduction: Despite treatment with adjuvant osimertinib, some patients experience relapse. NORA is a trial designed to identify persistent drug resistance (DTP) to neoadjuvant osimertinib in resectable non-small cell lung cancer (NSCLC) with EGFR mutations (NCT04816838). We aimed to identify tumor-surrounding cellular characteristics that change the tumor microenvironment (TME) after neoadjuvant osimertinib for surgically resected EGFR-mutant NSCLC. Methods: Neoadjuvant osimertinib was given daily for two 28-day cycles followed by surgical resection and adjuvant osimertinib for 3 years. We performed single-cell RNA sequencing (scRNA-seq) on samples from 25 patients with EGFR mutations (Exon 19 deletion, N=10; L858R, N=15) before (N=18) and after (N=24) osimertinib treatment. The analysis was based on the Scanpy package in python, and the interaction was performed with Liana. We divided the pathological response according to major pathological response (MPR, N=6) and non-MPR (N=19). Results: After 8 major clustering from total cells, 60 subclusters were divided. Among them, myeloid cells were classified into 14 clusters. We found 3 macrophage subclusters (MAC1-SELENOP, MAC3-SPP1, and MAC7-PLXDC2) that were significantly increased after treatment with neoadjuvant osimertinib. Macrophage polarization status using the signature scoring method showed that the M2 phenotype was the strongest in the MAC1-SELENOP subcluster, while the M0 signature was high in MAC3-SPP1, and the M1 signature was high in MAC7-PLXDC2. These three macrophage subclusters showed enrichment in lipid metabolism compared to those of pre-neoadjuvant samples. In addition, the MAC1-SELENOP subcluster was significantly increased in non-MPR patients compared to MPR patients. This finding is paramount since MAC1-SELENOP may play a role in modifying the TME through various interactions with epithelial cells with DTP signature. Conclusion: Among several subclusters, three macrophage clusters enriched in the post-osimertinib samples were associated with lipid metabolism. In particular, the MAC1-SELENOP cluster with a tumor-associated macrophages (TAMs) phenotype had multiple interactions with tumors. This may lead to reprogramming of cancer cells to survive in TMEs. These finding may be applied to identifying DTPs and discovering potential therapeutic applications. Citation Format: Su-Jin Choi, Jii Bum Lee, Hyo Sup Shim, Byung Jo Park, Chang Young Lee, Min Hee Hong, Byoung Chul Cho, Sun Min Lim. Reprogramming of the tumor microenvironment via lipid-associated macrophage subtypes after neoadjuvant osimertinib treatment in EGFR-mutantnon-small cell 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 6278.