Abstract 6829: Identification of immune suppressive features in tumor-associated endothelial cells (TECs) in EGFR-mutant non-small cell lung cancer via single-cell RNA sequencing
Authors: Choi Su-Jin , Lee Jii Bum , Pyo Kyoung-Ho , Lee Gang-Taik , Park YoungJoon , Lee You Won , Yun Mi Ran , Lim Kyumin , Lee JuHyeon , Hong Min Hee , Lim Sun Min , Cho Byoung Chul 
Published: March 2024

Abstract
Introduction: Within the tumor microenvironment (TME), tumor-associated endothelial cells (TECs) exhibit distinct features from normal cells, and diverse phenotypes of TECs result in intratumoral heterogeneity. Here, we aimed to characterize the phenotypes of the TECs of non-small cell lung cancer (NSCLC), identify distinct features that are pivotal in tumor progression, and discover potential therapeutic applications.
Methods: We performed single-cell RNA sequencing (scRNA-seq) from 128 NSCLC patients to include I (N=52), II (N=18), III (N=21), and IV (N=14), and compared them with normal cells (N=24). Epidermal growth factor receptor (EGFR)-mutant accounted for 69 samples. EGFR-wild (N=35) was further classified as programmed death-ligand 1 (PD-L1) high (N=14) and low (N=21) with PD-L1 high defined as tumor proportion score &gt; 50%.
Results: Twelve distinct EC types were characterized based on clinical information, including EGFR mutations and PD-L1 expression. We classified our subset as normal cells and tumor-enriched ECs, which were further classified as EGFR-wild or mutant ECs. Compared to normal cells, phenotypes such as activated post-capillary veins (APCVs), tip ECs, and endothelial mesenchymal transition (endoMT) ECs were predominantly observed in all tumor-enriched ECs. In EGFR-mutant ECs, ribosomal ECs, and vascular mimicry (VM) ECs were primarily enriched. Trajectory analysis showed that endoMT and VM ECs had lineage tracing of fibroblasts and epithelial cells, respectively. By clinical stage, APCVs, tip ECs, endoMT, and VM ECs were more enriched at advanced stages. PD-L1-high subset had higher expression of adhesion molecules, APCVs, and median transmigration score than other phenotypes. Also, high endothelial venules (HEVs) mediating lymphocyte trafficking to lymphoid organs were enriched in high PD-L1 subset. In the APCVs of EGFR-mutant group, there were interactions related to immune cell suppression and interactions of chemokines/chemokine receptors involved in recruitment.
Conclusion: Our findings reveal distinct phenotypes of ECs, including the enrichment of APCVs, tip ECs, and endoMT ECs in all tumor-enriched EC populations, as well as VM ECs in EGFR-mutant ECs. APCVs, which is abundant high PD-L1 subset, play a crucial role in the transmigration progress of immune cells across vascular endothelium. In EGFR-mutant NSCLC, dysfunctional immune cells are recruited into the tumor, along with relatively low transmigration, resulting in poor tumor-killing effect.
Citation Format: Su-Jin Choi, Jii Bum Lee, Kyoung-Ho Pyo, Gang-Taik Lee, YoungJoon Park, You Won Lee, Mi Ran Yun, Kyumin Lim, JuHyeon Lee, Min Hee Hong, Sun Min Lim, Byoung Chul Cho. Identification of immune suppressive features in tumor-associated endothelial cells (TECs) in EGFR-mutant non-small cell lung cancer via single-cell RNA sequencing [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 6829.