Smoking-Associated Alterations in Bronchoalveolar Lavage Fluid Microbiota and Metabolomic Profiles in Patients With Lung Cancer

Abstract Background Smoking is one of the most important modifiable risk factors for lung cancer. However, clinical evidence remains limited regarding whether smoking is associated with remodeling of the lower-airway microbiome and local metabolic networks in patients with lung cancer. Bronchoalveolar lavage fluid (BALF) may reflect the local lower-airway microenvironment, and integrated microbiome-metabolome profiling may help identify smoking-associated ecological and metabolic signatures. Methods Thirty-seven patients with pathologically confirmed lung cancer who underwent electronic bronchoscopy at the Second Hospital of Hebei Medical University between November 2022 and November 2023 were enrolled, including 22 smokers and 15 never-smokers. BALF samples were collected for 16S rRNA amplicon sequencing and untargeted metabolomic profiling. Smoking-associated microbial taxa, metabolites, and cross-omics associations were evaluated using LEfSe, KEGG enrichment, ROC curve analysis, and Spearman correlation analysis. Results A total of 1,378 operational taxonomic units were detected, including 1,004 shared OTUs. Alpha diversity did not differ significantly between groups, whereas weighted UniFrac PCoA showed significant separation in microbial community structure (PERMANOVA, P < 0.05). Bacteroidota, Actinomycetota, Prevotella, Schaalia, and Mobiluncus were relatively enriched in smokers, whereas Pseudomonadota, Finegoldia, Peptoniphilus, and Paracoccus were enriched in never-smokers. Untargeted metabolomics identified 23 differential metabolites, of which 18 were upregulated and 5 were downregulated in smokers. These metabolites were mainly enriched in glutathione metabolism, alanine metabolism, arginine and proline metabolism, bile secretion, ABC transporters, pantothenate and coenzyme A biosynthesis, and fructose and mannose metabolism. ROC analysis suggested potential discriminatory value for (Z)-11-hexadecenal, spermidine, oxosativene, nicotine N-oxide, and 1,2-dimethylimidazole (AUC 0.706–0.776). Mobiluncus was positively correlated with nicotine N-oxide, whereas Finegoldia was negatively correlated with dihydrothymine. Conclusions BALF from smokers with lung cancer showed local microenvironmental alterations characterized by microbial compositional remodeling and metabolic pathway perturbation. The observed Mobiluncus-nicotine N-oxide and Finegoldia-dihydrothymine associations are candidate microbiome-metabolome features that require validation in larger, well-matched cohorts.