Gut Microbiota Modulate CD8 T Cell Responses to Influence Colitis-Associated Tumorigenesis

There is increasing evidence that gut microbiome perturbations, also known as dysbiosis, can influence colorectal cancer development. To understand the mechanisms by which the gut microbiome modulates cancer susceptibility, we examine two wild-type mouse colonies with distinct gut microbial communities that develop significantly different tumor numbers using a mouse model of inflammation-associated tumorigenesis. We demonstrate that adaptive immune cells contribute to the different tumor susceptibilities associated with the two microbial communities. Mice that develop more tumors have increased colon lamina propria CD8+ IFNγ+ T cells before tumorigenesis but reduced CD8+ IFNγ+ T cells in tumors and adjacent tissues compared with mice that develop fewer tumors. Notably, intratumoral T cells in mice that develop more tumors exhibit increased exhaustion. Thus, these studies suggest that microbial dysbiosis can contribute to colon tumor susceptibility by hyperstimulating CD8 T cells to promote chronic inflammation and early T cell exhaustion, which can reduce anti-tumor immunity. [Display omitted] •Dysbiosis can lead to increased colon tumor susceptibility and CD8+ IFNγ+ T cells•Increased colon CD8+ IFNγ+ T cells are associated with more inflammation and tumors•Dysbiosis and increased tumorigenesis are associated with greater T cell exhaustion The gut microbiome is capable of modulating intestinal inflammation and tumorigenesis. Yu et al. demonstrate that dysbiosis can lead to increased susceptibility to inflammation-associated colon tumorigenesis via the induction of pro-inflammatory CD8+ IFNγ+ T cells, which can lead to increased T cell exhaustion within the tumor microenvironment.