PDCD1 and neoplasm: To examine the anti-tumor effect of PD-1/PD-L1 immune checkpoint blockade on metastasis liver tumors, liver lesions were induced by the intrasplenic injection of SL4 cells and then PRI-724 (0.4 mg/mouse) and/or anti-PD-L1 Ab (200 μg/mouse) were administrated to these animals.