Finally, Peng and colleagues analyzed the response to anti-PD-1/anti-programmed-death-ligand 1 (anti-PD-L1) therapy in a cohort of gastrointestinal malignances, including CRC, and reported that a high Prevotella/Bacteroides ratio positively correlates with response to CPIs [55]. Here, PDCD1 is linked to colorectal carcinoma.