CEACAM1 and neoplasm: F. nucleatum also supports tumor development by hampering anti-tumor immunity via mechanisms that include interfering with recruitment of tumor infiltrating lymphocytes (Mima et al., 2015; Chen et al., 2018; Hamada et al., 2018) and activating TIGIT and CEACAM1 immune checkpoints that inhibit killing of cancer cells by Natural Killer (NK) cells and tumor infiltrating T cells (Gur et al., 2015, 2019).