Microbiome-specific T follicular helper cells drive tertiary lympohid structures and anti-tumor immunity against colorectal cancer

Advanced or metastatic colorectal cancer is largely refractory to current therapeutic regimens and correspondingly has poor prognosis. The microbiota plays an important role in controlling the host immune response, with unique bacterial species able to activate and differenation specific subpopulations of T cells in the colon. Using an orthotopic carcinogen-induced murine model of colorectal cancer, we found that pertubation of the microbiome with Helicobacter hepaticus led to increased antitumor immunity and disease control. Single-cell RNAseq analysis was used to interrogate the tumor microenvironment and lamina propria in Helicobacter hepaticus colonized and control mice. Colitis-associated colon cancer was induced in 6 week old mice using the azoxymethane-dextran sodium sulfate (AOM-DSS) model. Mice were injected intraperitoneally with azoxymethane (AOM) followed by 3 cycles of 1 week of treatment with DSS in drinking water and 2 weeks without. One group of mice were colonized with Helicobacter hepaticus (AOM-DSS+HHep) on week 7 post tumor inducation, and uncolonized mice were carried forward as a control. Single cell suspensions were generated from the epithelial layer containing the tumor and the lamina propria of mice 12 weeks after tumor induction. Three mice were used in each group, and cells from individual mice for each tissue were cell hashed with Biolegend TotalSeq-C. TotalSeq-C 1-3 labeled the individual mice from the AOM-DSS group, and TotalSeq-C 4-6 labeled the individual mice from the AOM-DSS+HHep group.