Bacteria Ammoniphilus Associated with High Tertiary Lymphoid Structures in Lung Squamous Cell Carcinoma 2248408

Abstract Introduction Non—small cell lung cancer (NSCLC) is the leading cause of cancer death, and robust biomarkers predicting prognosis and/or efficacy of treatment are urgently needed. Tertiary lymphoid structures (TLSs) are recognized as predictors of response to immune checkpoint inhibitors. Tumor-resident bacteria have been shown to promotes TLSs formation. We hypothesized that bacteria in TLSs-high tumors could predict TLSs abundance and ICI responsiveness. Methods We reviewed resected cases of lung squamous cell carcinoma (LUSC) from a larger NSCLC cohort collected between 2013 and 2016. Of 39 cases, 24 met prespecified criteria. TLSs status was determined by PNAd+ high endothelial venule (HEV) immunohistochemistry. Twelve tumors were classified as TLSs-high and 12 as TLSs-low. Bacterial communities were profiled by 16S rRNA(V3—V4) sequencing and processed with QIIME2/DADA2. Differential taxa were identified with LEfSe (α =0.05, LDA>2.0). Functional profiles were inferred by PICRUSt2 and tested with STAMP (FDR-corrected q < 0.05). Results Bacteria specific to the TLS-high group were identified. Genus Ammoniphilus was enriched in TLS-high tumors (7/24; LDA 5.026; p = 0.033). Genus Ralstonia was more prevalent in adjacent normal tissues of TLS-high cases (8/24; LDA 4.367; p = 0.006). Functional analysis suggested that Ammoniphilus was involved in methionine, nucleotide, and energy metabolism pathways. Conclusion We identified Ammoniphilus as a first-in-LUSC candidate microbiome linked to TLSs formation. Its presence could indicate an immunologically “hot” tumor microenvironment and serve as a novel biomarker predicting response to immune checkpoint inhibitors. Funding Source n/a. Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)