Significance of Tumor Microvasculature in the Tumor Microenvironment in Adenocarcinoma with EGFR Common Mutations.

Background: Tumor microvasculature is an important component of the tumor microenvironment (TME), and it has been reported that tumor microvasculature induces TME to become immunosuppressive via vascular endothelial growth factor. However, the significance of this in adenocarcinoma with epidermal growth factor receptor (EGFR) common mutations has not been fully investigated.

Methods: We analyzed 262 patients with adenocarcinoma harboring EGFR common mutations who underwent surgery at Kyushu University Hospital between 2006 and 2021. Microvessel density (MVD) was calculated by CD34 immunohistochemistry. Patients were categorized into high and low MVD status, which was compared with the clinicopathological characteristics.

Results: A total of 136 (51.9%) patients had L858R mutation, and 126 (48.1%) had Exon 19 Del. Regarding MVD status; 133 patients (50.8%) were classified as high and 129 (49.2%) as low. Fisher's exact test revealed a significant association of high MVD status with high CD8+ tumor infiltrating lymphocytes (TILs) (p = 0.0187), low GZMB+ TILs (p = 0.0019), and high Foxp3+ TILs (p = 0.0003). On multivariate analysis, MVD status was significantly associated with Foxp3+ TILs and GZMB+ TILs. Fisher's exact test also revealed that tumors with L858R mutation had a high MVD status (p = 0.0136) compared with tumors with deletions of exon 19 (Exon 19 Del), and multivariate analysis revealed that L858R mutation was significantly associated with high MVD status.

Conclusions: In adenocarcinomas harboring EGFR common mutations, abundant tumor microvasculature might induce the TME to be immunosuppressive. Tumors with L858R mutation compared with Exon 19 Del might be more likely to form an immunosuppressive TME owing to the abundance of tumor microvasculature.