Special tissue microbiota such as Cyanobacteria are associated with the immune microenvironment of lung adenocarcinoma.

Background: Lung cancer is the leading prevalent form of human cancer and has the highest mortality rate among all cancer types. The role and potential mechanism of the lung microbiome in lung cancer is still unknown. This study aims to investigate the microbiomes of lung cancer patients possessing different levels of infiltrated CD8⁺ T cells and programmed cell death-1 (PD-1) receptors, and further assess the correlation between specific microbes and the immune environment of lung tumor.

Methods: We analyzed the microbiomes of lung cancer tissues from patients with different levels of infiltrated CD8⁺ T cells and PD-1 expression using 16S rRNA gene sequencing. The relative abundance of dominant phyla and genera was compared, and the correlation between microbial composition and immune markers was explored.

Results: Our results showed that lung cancer tissues displayed similar microbiome profiles, including Proteobacteria, Bacteroidetes, and Actinobacteria as the dominant phyla; and Chryseobacterium, Triticum aestivum (bread wheat), and Acinetobacter as the dominant genera. We found that the relative abundance of Chryseobacterium was positively correlated with CD8⁺ T cell infiltration and the level of PD-1 expression, while the relative abundance of Acinetobacter was negatively associated with the PD-1 level. In addition, higher beta diversity was identified in samples with low CD8⁺ T cell infiltration, but no significant correlation between beta diversity and PD-1 expression was observed. Furthermore, the relative abundance of Cyanobacteria was significantly higher in both the CD8 high and PD-1 high groups.

Conclusions: Our study indicated that the lung microbiota played an indispensable role in the CD8⁺ T cell-mediated tumor immune response. These findings shed light on valuable insights into the intricate interplay between the lung microbiome and the immune system in the progression of lung cancer, offing potential therapeutic strategies targeting the lung microbiome.