PDCD1 and metastatic neoplasm: In addition, instead of decreased Treg percentages in SubQ‐only mice (Figure 2B), anti‐PD‐1 enhanced Treg populations in both tumor sites of CSLT mice (Figure 2C), consistent with the previous notion that Tregs controlled the suppression of distant tumor immunity in the presence of liver tumors.[10] Taken together, these data suggested that metastatic tumors growing in the liver could impact systemic responses of major immune populations toward PD‐1 blockade in vivo.