New research provides insights that help explain how a common oral bacterium, often enriched in the tumors of patients with colorectal cancer, can promote tumor progression. A team led by investigators at the Hebrew University Hadassah Medical School found that the oral pathogen Fusobacterium nucleatum can protect tumor cells from being destroyed by immune cells (Gur C et al. Immunity. 2015;42:344-355).
Using a library of F nucleatum mutants, the researchers discovered that the immune evasion of tumor cells depends on the binding of the bacterial Fap2 protein to TIGIT (T-cell immunoglobulin and ITIM domain), a receptor present on all human natural killer cells and various T cells that inhibits cytotoxic immune activity. The vast majority of tumor-infiltrating lymphocytes within colon tumors were found to express TIGIT.
Hampton T. Bacteria Protect Colorectal Cancer Cells From Immune Destruction. JAMA. 2015;313(13):1305. doi:10.1001/jama.2015.2854