CEACAM1 and neoplasm: Fap2, an outer surface protein of F. nucleatum, binds to and activates the inhibitory receptors, T cell Ig, ITIM Domain receptor (TIGIT)42, and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1)107 expressed by T cells and NK cells, which protect F. nucleatum and tumor cells from being killed by immune cells.