In a mouse model of carcinogen-induced colorectal cancer (CRC), Overacre-Delgoffe et al. found that colonization by an immunogenic bacterium (Hhep) restricted tumor growth and extended mouse survival. Hhep colonization led to lymphangiogenesis, infiltration of CD4+ T cells, B cells, and CD11c+ cells, and formation of tertiary lymphoid structures (TLS). Hhep- specific Tfh cells were detected in TLS following Hhep colonization, and loss of CD4+ T cells (or specifically Tfh) decreased TLS formation, immune infiltration, and tumor control. In TCGA data, a high Tfh signature was associated with improved progression-free survival in patients with CRC.
Contributed by Alex Najibi
ABSTRACT: The composition of the intestinal microbiota is associated with both the development of tumors and the efficacy of anti-tumor immunity. Here, we examined the impact of microbiota-specific T cells in anti-colorectal cancer (CRC) immunity. Introduction of Helicobacter hepaticus (Hhep) in a mouse model of CRC did not alter the microbial landscape but increased tumor infiltration by cytotoxic lymphocytes and inhibited tumor growth. Anti-tumor immunity was independent of CD8(+) T cells but dependent upon CD4(+) T cells, B cells, and natural killer (NK) cells. Hhep colonization induced Hhep-specific T follicular helper (Tfh) cells, increased the number of colon Tfh cells, and supported the maturation of Hhep+ tumor-adjacent tertiary lymphoid structures. Tfh cells were necessary for Hhep-mediated tumor control and immune infiltration, and adoptive transfer of Hhep-specific CD4(+) T cells to Tfh cell-deficient Bcl6(fl/fl)Cd4(Cre) mice restored anti-tumor immunity. Thus, introduction of immunogenic intestinal bacteria can promote Tfh-associated anti-tumor immunity in the colon, suggesting therapeutic approaches for the treatment of CRC.