PDCD1 and neoplasm: Therefore, we used the CT26 mouse model to evaluate the effect of zosuquidar on tumor growth, which is categorized as a highly immunogenic tumor model and widely used in PD‐1‐PD‐L1 related studies.[22, 23] BALB/c mice bearing CT26 cells were treated with zosuquidar, PD‐1 monoclonal antibody (mAb), and control, respectively (Figure 2A).