PDCD1 and neoplasm: To evaluate the impact of liver metastasis on systemic immune reactions and responses to anti‐PD‐1 treatment, we developed a mouse model based on a two‐site tumor system with concurrent implantation of SubQ and liver tumor to mimic the liver metastasis as previously described.[29] Specifically, we established liver metastases by injecting MC38 tumor cells to partially‐removed spleens, and SubQ tumors were injected 2 days after the splenic inoculation (Figure 1A).