Background: Accumulating evidence links the intestinal microbiota and colorectal carcinogenesis. Fusobacterium nucleatum has been shown to promote colorectal tumor growth and inhibit antitumor immune responses. Emerging evidence demonstrates an enrichment of Fusobacterium species in colorectal cancer live metastasis (CRLM).

Aim: To test the hypothesis that higher amount of Fusobacterium nucleatum is associated with lower density of CD8+ T-cells in CRLM.

Method: Genomic DNA was extracted from CRLM and adjacent normal liver tissues. We measured the amount of Fusobacterium nucleatum DNA in 164 CRLM tissues using a quantitative polymerase chain reaction assay. The density of CD8+ T-cells in CRLM was determined by immunohistochemical staining.

Result:Fusobacterium nucleatum was detected in 8 (4.9%) of 164 CRLM cases. A higher density of CD8+ T-cells in CRLM was significantly associated with better relapse-free survival (P =0.036). Fusobacterium nucleatum-negative cases, Fusobacterium nucleatum-positive cases were inversely associated with the density of CD8+T-cells (P =0.020).

Conclusions: The presence of Fusobacterium nucleatum is inversely associated with CD8+ T-cells density in CRLM. Upon validation, our data may have implications for preventing the formation of liver metastases in colorectal cancer through targeting intestinal microflora.

Citation Format: Yuki Sakamoto, Kosuke Mima, Nobuya Daitoku, Yukiharu Hiyoshi, Katsunori Imai, Masaaki Iwatsuki, Takatsugu Ishimoto, Yoshifumi Baba, Shiro Iwagami, Yuji Miyamoto, Yoichi Yamashita, Naoya Yoshida, Hideo Baba. Fusobacterium nucleatum and T cells in colorectal cancer liver metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2837.