Recombinant programmed cell death protein 1 functions as an immune check point blockade and enhances anti-cancer immunity

Effective cancer therapy aims to treat not only primary tumors but also metastatic and recurrent cancer. Immune check point blockade-mediated immunotherapy showed promising effect against tumors; however, it still has a limited effect in metastatic or recurrent cancer. Here, we extracted recombinant murine programmed death-1 (rmPD-1) proteins. The extracted rmPD-1 effectively bound to CT-26 and 4T1 cells expressing PD-L1 and PD-L2. The rmPD-1 did not alter the activation of dendritic cells (DCs); however, rmPD-1 promoted T cell-mediated anti-cancer immunity against CT-26 tumors in mice. Moreover, rmPD-1 decorated thermal responsive hybrid nanoparticles (piHNPs) promoted apoptotic and necrotic cell death of CT-26 cells in response to laser irradiation at 808 nm consequently, it promoted anti-tumor effects against the 1st challenged CT-26 tumors in mice. In addition, piHNP-mediated cured mice from 1st challenged CT-26 was also prevented the 2nd challenged lung metastatic tumor growth, which was dependent of cancer antigen-specific memory T cell immunity. It was also confirmed that the lung metastatic growth of 2nd challenged 4T1 breast cancer was also prevented in cured mice from 1st challenged 4T1 by piHNP. Thus, these data demonstrate that rmPD-1 functions as an immune checkpoint blockade for the treatment of tumors, and piHNPs could be a novel therapeutic agent for preventing cancer metastasis and recurrence.