Bronchoalveolar lavage microbiota signatures and stage-associated alterations in early-stage and advanced-stage non-small cell lung cancer: a pilot study.

OBJECTIVES

The aims of this study were to characterize the microbial flora in the bronchoalveolar lavage fluid (BALF) of patients with early-stage (stage I, II, IIIA) and advanced-stage (stage IIIB, IIIC, IV) non-small cell lung cancer (NSCLC), and to explore the associations between microbial flora and lung cancer stage.

METHODS

We collected BALF from NSCLC patients (early-stage group 26 cases; advanced-stage group 31 cases). Absolute quantitative metagenomic sequencing was performed to identify differential taxa, genes, and enriched pathways. Flow cytometry was used to profile T cell subsets. We correlated the microbial species with immune cell and gene expression. Receiver operating characteristic (ROC) curve analysis was performed to assess the ability of differential taxa to distinguish advanced-stage from early-stage NSCLC.

RESULTS

Dokdonia (q = 0.040, LDA = 5.704) and Cocleimonas (q = 0.026, LDA = 5.329) were enriched in the early-stage group, whereas Barnesiella (q = 0.046, LDA = 4.784), Pedobacter (q = 0.040, LDA = 4.913) and unclassified Bacteroides (q = 0.046, LDA = 4.932) were significantly enriched in the advanced-stage group. The microbial genes gmhD (q < 0.001, LDA = 3.926), rfaD (q < 0.001, LDA = 3.918), nudF (q = 0.004, LDA = 4.283) and sfsA (q = 0.004, LDA = 3.915) were expressed remarkably in the advanced-stage group. The advanced-stage group exhibited altered T cell subset distributions, including a higher proportion of CD8⁺ T lymphocytes (q < 0.001), whereas it showed a lower proportion of CD4⁺ T cells and a decreased CD4/CD8 ratio (q < 0.001; q < 0.001). Bifidobacterium was negatively associated with the CD4/CD8 ratio (q = 0.015) and positively significant correlated with the genes which enriched in the advanced-stage group.

CONCLUSIONS

This study delineated the microbial structure and function of early-stage and advanced-stage of NSCLC. We identified discriminating taxa, genes, and pathways linked to cancer progression, characterized the T cell subset distributions in the advanced-stage of NSCLC. Bifidobacterium abundance was associated with altered T cell subset distributions and stage-related microbial genes, providing hypotheses for future mechanistic studies on microbiota-driven NSCLC progression.