Modification of sPD1 with CRT induces potent anti-tumor immune responses in vitro and in vivo

Abstract As a key factor for tumor occurrence and development, tumor cells escape immune surveillance and inhibit the body immune killer effect through negative signaling pathways. In this research, we designed and expressed the fusion protein CRT-sPD1 to block PD1/PDL1 negative signal pathway, indirectly bind CRT to the tumor cell surface and to increase the cell immunogenicity activity. Results from western blotting, flow cytometry (FCM) and ELISA showed that the cell lines that stably express CRT, PD1 and CRT-sPD1 protein were obtained and the transfected cellular supernatant contained PD1 and CRT-sPD1 could bind to PDL1 on the surface of EL4 cells. Vitro experiments indicated the secreted mCRT-sPD1 protein could bind to PDL1 and enhance lymphocyte proliferation and CTL activity. We also found that fusion protein CRT-sPD1 could activate and induce the immune system to kill the tumor cells, specifically inhibit the tumor growth and prolong the survival period in mouse tumor model. And all these suggested that CRT-sPD1 could be used as drug development and utilization of cancer immunotherapy.