Tumor Suppression by PD-1/PD-L1 Interaction Blockage in Mice Model

Background: Overexpression of programmed cell death ligand 1 (PD-L1) in tumor cells and subsequent interaction with the pro-grammed cell death protein 1 (PD-1) in tumor-infiltrating T cells cause an immune evasion of the tumor from cytotoxic T-cells. There-fore, inhibiting such interaction by a recombinant PD-1 can hinder tumor growth and extend the survival rate. Methods: The mouse extracellular domain of PD-1 (mPD-1) was expressed in E. coli BL21 (DE3) strain and purified using nickel affinity chromatography. The binding ability of the purified protein to human PD-L1 was studied using ELISA. Finally, the tumor-bearing mice were used to evaluate the potential antitumor effect. Results: The recombinant mPD-1 showed a significant binding capacity to human PD-L1 at the molecular level. The tumor size sig-nificantly decreased in the tumor-bearing mice after the intra-tumoral injections of mPD-1. Moreover, the survival rate increased significantly after eight weeks of monitoring. The histopathology revealed the necrosis in the tumor tissue of the control group compared to the mPD-1 received mice. Conclusions: Our outcomes propose that interaction blockade between PD-1 and PD-L1 is a promising approach for targeted tumor therapy.