Revealing distinct immune landscape in EGFR mutant and EGFR wild type lung adenocarcinoma by using single-cell RNA sequencing

e21008 Background: Non-small cell lung cancer (NSCLC) with EGFR mutations displays heterogeneity in the extent of intratumoral immunocytes infiltration compared to those with EGFR wild types, which may explain their variable responsiveness to PD-1 blockade. Here, we performed single-cell RNA sequencing (scRNA-seq) to unveil the immunescape and heterogeneity of lung adenocarcinoma (LUAD) between EGFR mutant (EGFR-mut) patients and wild type (EGFR-wt) patients. Methods: Eleven EGFR-mut and 7 EGFR-wt NSCLC tumor samples were analyzed. Immune cells (CD45+) were enriched through fluorescence-activated cell sorting (FACS) and subjected to single-cell RNA sequencing (scRNA-seq) using the 10X Genomics platform. Sequencing reads were normalized and analyzed using the R/Seurat package. Cellular components of each sample were determined based on known marker genes. Wilcox test was used to compare promotion by subtype composition and immune cell infiltrates. Results: Different immune cell compositions were observed between EGFR-mut and EGFR-wt LUAD tumor samples. We found EGFR-wt tumors are marked by an enrichment of CCL15+ tumor-associated macrophages(TAMs), which display pro-inflammatory properties and high expressions of TNF-a-signaling genes. In contrast, EGFR-mut tumors exhibit enrichment of SPARCL1+TAMs, which are involved in epithelial-mesenchymal transition (EMT) and angiogenesis. EGFR-wt tumors exhibited enrichment of CD8-Teff-MX1 and Gamma delta T cells, both of which displayed higher cytotoxic and naive features. Moreover, the high expression of Gamma delta T corresponds with a better clinical prognosis. In contrast, CD8-Teff-XCL1 and NKT-FGFBP2 were found enriched in EGFR-mut tumors, both of which contributed to higher exhaustion and decreased cytotoxic function. Additionally, NK-IL32 was found enriched in EGFR-mut tumors, showing a downregulated T cell receptor signaling and stronger exhausted features. The high expression of this subcluster correlated with poor outcomes in LUAD patients harboring EGFR mutation. Conclusions: Our study provided a deeper understanding of the immune landscape of EGFR-mut and EGFR-wt LUAD and gained better insights into the immunological mechanisms involved in the response to ICIs. The results of our study could be instructive for the development of future immunotherapy strategies for NSCLC patients harboring EGFR mutations.