Multi-Site Microbiome Profiling Reveals Gastrointestinal-Pulmonary Microbial Associations in Multiple Primary Lung Cancer

Multiple primary lung cancer (MPLC) is a distinct subtype of lung cancer characterized by the presence of two or more independent lesions within the lungs. Increasing evidence suggests that microbial dysbiosis may play a role in lung carcinogenesis; however, the microbial characteristics associated with MPLC development remain unclear. In this study, we performed full-length 16S rRNA gene sequencing on 176 samples collected from 21 MPLC patients across seven sampling sites. Bacterial diversity and community composition differed significantly across sampling sites. The oral cavity and upper gastrointestinal tract (UGI) exhibited the highest richness and a similar microbial profile, while lung tissue and respiratory tract samples harbored less diverse but compositionally related communities. Microbial source tracking revealed that a subset of bacteria in pulmonary nodules originated from the UGI tract, suggesting possible microbial translocation associated with gastroesophageal reflux. Phylogenetic analysis further identified two species, Prevotella melaninogenica and Gemella haemolysans, as the most frequently shared taxa in the lung and UGI microbiota of MPLC patients, potentially contributing to tumorigenesis. Furthermore, analysis of the lung microbiota revealed microbial heterogeneity among pulmonary nodules in MPLC patients, underscoring the need to analyze each nodule independently. This study provides a comprehensive characterization of the microbiota in MPLC patients and highlights potential microbial links between the gastrointestinal and pulmonary systems.