PDCD1 and neoplasm: The tumor weight at the 39th post-implantation day was 5.7 ± 0.5, 4.6 ± 0.8, 1.8 ± 1.7, 2.7 ± 1.0, 0.8 ± 0.7, and 2.0 ± 1.8 g for control, cimetidine, anti-PD-1, anti-PD-1 plus cimetidine, anti-PD-L1, and anti-PD-L1 plus cimetidine, respectively (Figure 5).