Revealing the role of lung cancer microbiota in the tumor progression

Abstract Lung cancer (LC) remains as the leading cause of death by cancer worldwide. In Chile, LC is the second cause of cancer-related deaths. Recently, studies in melanoma and non-small cell lung cancer (NSCLC) patients have highlighted the role of the gut microbiota as an important host factor in mediating the responses/resistance to immunotherapy, suggesting that bacteria present in the gut may modulate the immune response in these tumors. However, the role of extra-intestinal microbiota; bacteria living outside of the gut, in cancer pathogenesis and the response to anti-cancer therapies remains largely undetermined. Here we characterize the composition of intratumoral microbiota of NSCLC and seek to establish a functional relationship between it and the composition of the immune microenvironment and the clinicopathological characteristics of NSCLC patients. From the first 157 FFPE NSCLC samples, we extracted DNA from all collected samples, obtaining adequate material in quality and quantity to later be submitted for analysis to 16S sequencing. Using 16S rRNA gene sequencing, we assessed the general landscape of the NSCLC tumor microbiome, revealing the presence of large number of bacterial communities in the NSCLC tumor samples on the different histological subtypes analyzed. We have detected differences in alpha diversity in the histological subtypes studied. Even more interesting, we have detected significant differences in lung adenocarcinoma depending on the degree of histological differentiation, observing a decrease in proteobacteria and an enrichment of Bacteroidales, as cell differentiation is lost. Additionally, we identified taxonomic differences between differentiated and undifferentiated tumors. Differentiated tumors show enrichment in Akkermansia muciniphila and while undifferentiated tumors show enrichment in Actinobacter Corynebacterium. Suggesting that these taxa could contribute to maintaining a differentiated state or inducing cell dedifferentiation, respectively. Our results reveal the presence of a large number of bacterial communities in lung cancer samples in the different histological subtypes analyzed. Suggesting that these communities could play a key role in tumor differentiation and progression.