Fig. 6: Colonization of metastases by tumor-associated bacteria is related to oxygen tolerance and metabolic capacities.
From: Primary tumor microbiomes predict distant metastasis of colorectal cancer
A In the ORIEN cohort, relative abundance comparison to primary tumors showed metastasis depletion of Fusobacterium spp., Bacteroidaceae, and Bifidobacterium spp., among others, while Enterobacteriaceae and Bacillus spp. were unchanged or enriched. B A similar analysis in the UIHC cohort identified similar patterns, except that Fusobacterium was not significantly depleted. C The Protrait database was used for enrichment analysis of bacterial functions based on taxonomy and relative abundance in the ORIEN cohort. Anaerobic bacteria were depleted in metastases, as well as H2S-producers and bacteria with the capacity to utilize certain sugars. The findings may reflect key selective pressures in the metastasis microenvironment, which tends to be oxygenated and likely lacks the diet-derived carbon sources available to bacteria in the gut. D Picrust2 predicted pathway analysis of the UIHC cohort identified modest enrichment of nucleic acid metabolism and peptidoglycan-related pathways in metastasis microbiomes. No pathways were significantly enriched in primary tumors.
