PDCD1 and neoplasm: At day 24, the mean tumor volume of CT group (both anti-PD-1 antibody and probiotics; mean tumor size ± SEM = 1,681.02 ± 77.86 mm3) was the smallest, followed by MC group (received anti-PD-1 antibody but not probiotics; mean tumor size ± SEM = 2,511.05 ± 83.64 mm3), PA group (received probiotics but not anti-PD-1 antibody; mean tumor size ± SEM = 2,867.67 ± 144.60 mm3), and NC group (did not receive probiotics nor anti-PD-1 antibody; mean tumor size ± SEM = 3,695.74 ± 134.39 mm3) (Figure 1B).