Country-specific differences in the lung tumour microbiome.

Abstract

e20044 Background: Sputum examination for the early detection of lung cancer continues to be explored ( Thunnissen 2003 ), however has so far resulted in a low diagnostic yield. An increasing number of studies have evidenced a mechanistic role of the lung microbiome in the induction of lung cancer ( Liu et al., 2020 ), and the presence of bacterial biomarkers in bronchoalveolar lavage and sputum have been proposed ( Cheng et al., 2020 ). It is currently unknown whether the sputum microbiome can appropriately capture the lung tumour microbiome. Given that the lung microbiome may vary by geography, this analysis was considered over two populations: China and Italy. Methods: Microbiome analysis was performed using BioCorteX’s industry-leading knowledge graph and integrated proprietary engines v20240126_153156. Data from 9 studies was used. In total, 461 samples from lung cancer patients in China (250 sputum, 211 tumour) and 60 from Italy (34 sputum, 26 tumour) were considered. Shannon’s diversity was used to consider within-sample diversity, and dimensional scaling based (MDS) on Bray-Curtis diversity was used to consider between-sample diversity. Results: All sample were checked to have a library size greater than 100, and more than 10 unique species. Only those species present in over 1% of samples were considered to reduce noise. In both China and Italy, tumour samples had a lower diversity than sputum samples (p = 0.00016 and p < 2.2e-16, respectively). Samples from Italy had a lower diversity than samples from China (p < 2.22e-16). In the MDS analysis, the tumour samples from China and Italy formed two distinct, non-overlapping clusters. A third cluster was formed from the union of sputum samples from both countries. These results were independent of any study-specific effects. Conclusions: These results indicate that the sputum microbiome is not representative of the tumour microbiome, and that the divergence of the tumour microbiome away from the sputum microbiome is country specific. The results of this analysis highlight that further work into differences in the lung tumour microbiome by country is warranted, especially in light of the growing body of evidence suggesting a causative role of the microbiome in lung cancer. It is also possible that lung cancer treatments may be impacted by the country-specific nature of the lung tumour microbiome.