Lower Respiratory Tract Microbiome Signatures of Health and Lung Cancer Across Different Smoking Statuses

Background: The respiratory microbiota is pivotal in maintaining pulmonary health and modulating disease; however, the intricate interplay between smoking, lung cancer, and microbiome composition remains incompletely understood. Here, we characterized the lower respiratory tract microbiome in a Russian cohort of 297 individuals, comprising healthy subjects and lung cancer patients of different smoking statuses (current smokers, former smokers, and nonsmokers). Methods: Using next-generation sequencing of the 16S rRNA gene from unstimulated sputum samples, we identify distinct microbiota signatures linked to smoking and lung cancer. A PERMANOVA (Adonis) test and linear discriminant analysis effect size were used for statistical analysis of data. Results: In healthy individuals, smoking did not affect microbiome diversity but markedly altered its composition, characterized by an increase in Streptococcus and a reduction in Neisseria as well as other genera such as Fusobacterium, Alloprevotella, Capnocytophaga, and Zhouea. Healthy former smokers' microbiota profiles closely resembled those of healthy nonsmokers. In lung cancer patients, microbiome diversity and composition were minimally impacted by smoking, possibly due to the dominant influence of tumor-microenvironment-related factors. Nevertheless, Neisseria abundance remained significantly lower in smokers across advanced-stage lung cancer. Lung cancer patients exhibited distinctive microbiota signatures, including enrichment of Flavobacteriia, Bacillales, and Pasteurellales and depletion of Alphaproteobacteria, Coriobacteriaceae, and Microbacteriaceae, irrespective of smoking status. Conclusions: Our findings emphasize the profound impact of smoking on healthy respiratory microbiota which may be masked by lung-cancer-related factors. These insights highlight the necessity of considering smoking status in microbiome studies to enhance the understanding of respiratory health and disease.