Metagenomic sequencing of the upper bronchial tract microbiome of patients with and without lung cancer. Metagenomics of the Lung Cancer Microbiome

The lung microbiome in patients with lung cancer (LC) is poorly defined. Spontaneous sputum samples were collected from ten patients referred with possible LC, of which four were eventually diagnosed with LC (LC+), and six had no LC after one year (LC-). Principal component analysis of taxonomic alignments showed some separation between LC+ and LC-, and was not influenced by smoking status. Of the seven bacterial species found in all samples, Streptococcus viridans was significantly higher in LC+ samples. Seven further bacterial species were found only in controls, and 16 were found only in samples from LC+. Additional taxonomic differences were identified in regards to significant fold changes between LC and controls cases, with five species having significantly higher abundances in LC+. Functional differences, evident through significant fold changes, included polyamine metabolism and iron sidrephore receptors. Granulicatella adiacens abundance was correlated with six other bacterial species in LC+ samples only. Further, bacterial species could also be related to LC stage. This study offers a novel insight into the functional capacity and species-level taxonomy of the sputum microbiome LC patients. Furthermore, it suggests G. adiacens as a novel and clinically useful biomarker for LC status and stage.