Engineering Chimeric Antigen Receptor T cells Against Immune Checkpoint Inhibitors PD-1/PD-L1 for Treating Pancreatic Cancer

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a 5-year survival rate of 6%. Major obstacles to successful treatment of pancreatic cancer are the immunosuppressive tumor microenvironment (TME) and antigenic complexity or heterogeneity. Programmed death-ligand 1 (PD-L1) is expressed on PDAC and immunosuppressed cells within the TME, providing suitable immunotherapy targets. We applied a chimeric antigen receptor (CAR) strategy to target immune checkpoint PD-1/PD-L1 interactions. Lentiviral vectors were used to express the extracellular domain of human PD-1 (PD1ACR) or the scFv region of aPD-L1 (PDL1CAR) that bind to PD-L1, and each was fused to intracellular signaling domains containing CD3 zeta, CD28, and 4-1BB (CD137). Both engineered CAR T cells recognized and eliminated PD-L1-overexpressing CFPAC1 cells efficiently at approximately 80% in vitro. Adoptive transfer of both CAR T cells enhanced T-cell persistence and induced specific regression of established CFPAC1 cancer >80% in a xenograft model. Ki67 expression in tumors decreased, whereas proinflammatory cytokines/chemokines increased in CAR T-cell-treated mouse sera. PD1ACR and PDL1CAR obtained a similar therapeutic efficacy. Thus, these armed third-generation PD-L1-targeted CAR T cells confer antitumor activity and ability to combat T-cell exhaustion, providing a potentially new and innovative CAR T cell immunotherapy against pancreatic cancers.