PDCD1 and colorectal cancer: In a study comparing the combination treatment of anti-Programmed cell Death 1 (PD-1) therapy and with anti-PD-1 therapy alone in a mouse model of colorectal cancer, the combination treatment was more effective than anti-PD-1 therapy alone, and Bacteroides stercoris was one of the intestinal bacteria involved in the metabolic changes in the combination group, with a higher abundance in the combination group [37].