Inflammation mediated by gut microbiome alterations promotes lung cancer development and an immunosuppressed tumor microenvironment

Accumulating evidence indicates that the gut microbiome influences cancer progression and therapy. We recently showed that progressive changes in gut microbial diversity and composition are closely associated with tobacco-associated lung adenocarcinoma (LUAD) in a human-relevant mouse model. Furthermore, we demonstrated that the loss of the antimicrobial protein Lcn2 in these mice, exacerbates pro-tumor inflammatory phenotypes while further reducing microbial diversity. Yet, how gut microbiome alterations impinge on LUAD development remains poorly understood. Here, we investigated the role of gut microbiome changes in LUAD development using fecal microbiota transfer and delineated a pathway by which gut microbiome alterations incurred by loss of Lcn2 fostered the proliferation of pro-inflammatory bacteria of the genus Alistipes, triggering gut inflammation. This inflammation propagated systemically, exerting immunosuppression within the tumor microenvironment, augmenting tumor growth through an IL-6-dependent mechanism and dampening response to immunotherapy. Corroborating our preclinical findings, we found that patients with LUAD with a higher relative abundance of Alistipes species in the gut showed diminished response to neoadjuvant immunotherapy. These insights reveal the role of microbiome-induced inflammation in LUAD and present new potential targets for interception and therapy.