Tumor Microenvironment Properties are Associated With Low CD68-positive Cell Infiltration and Favorable Disease-free Survival in EGFR-mutant Lung Adenocarcinoma.

BACKGROUND: The benefits of immune checkpoint inhibitors for first-line treatment in patients with lung adenocarcinoma harboring EGFR mutations are unclear. The effects of ICIs depend on the tumor microenvironment (TME). Differences in TME properties between mutant and wild-type EGFR have not been fully characterized.

PATIENTS AND METHODS: We collected 105 surgically resected (50 EGFR mutated and 55 EGFR wild-type), treatment-naïve lung adenocarcinoma tissues with clinical data to investigate the landscape and compartmentalization of tumor-infiltrating immune cells with respect to EGFR status by immunohistochemistry. The normalized FPKM values of data for 531 patients were obtained from The Cancer Genome Atlas (TCGA) Data Portal (https://portal.gdc.cancer.gov/).

RESULTS: CD68-positive cells within the tumor niche exhibited more intensive infiltration in wild-type EGFR than in mutations, and was related to lymph node invasion. In the RNA-Seq analysis, MMP9 and VEGFA showed higher levels in wild-type EGFR than in mutant cases. The EGFR mutation independently predicted a favorable disease-free survival.

CONCLUSION: The CD68-positive cells play a crucial role in discriminating the TME between different EGFR statuses.