PDCD1 and colorectal carcinoma: nucleatum-derived succinic acid could inhibit the cGAS interferon-β pathway, consequently dampening the antitumor response by limiting CD8+ T-cell trafficking to the tumor microenvironment.174 It is known that programmed cell death protein 1 (PD-1), when bound to its ligand PD-L1, can inhibit T-cell activation and contribute to impaired antitumor immune responses.175 Recently, Gao et al.176 found that the presence of F. nucleatum was correlated with an improved therapeutic response to PD-1/PD-L1 blockade to modulate immune checkpoint therapy for patients with CRC.