Mesothelin CAR-T Cells Secreting PD-L1 Blocking ScFv for Pancreatic Cancer Treatment

PD-1/PD-L1 pathway caused immunosuppression accounts, at least partly, for the poor therapeutic effect of Chimeric Antigen Receptor T (CAR-T) on solid tumors. In this study, we designed and prepared CAR-T cells that could secrete PD-L1 blocking antibody and target Mesothelin antigen (Sec-MesoCAR-T), to remove the immunosuppressive effect of tumor on CAR-T cells, thereby increasing the therapeutic effect of CAR-T cells on pancreatic cancer. The CAR-T cells that could not secret PD-L1 blocking antibodies (MesoCAR-T) were used as a control. Sec-MesoCAR-T cells showed an enhanced inhibitory effect on BxPC-3 tumor than MesoCAR-T cells in vitro and in vivo. Besides, Sec-MesoCAR-T cells secreted higher level of cytokines including IL-2, IL-6 and IFN-γ in vitro than MesoCAR-T cells. Following injection, there were significantly more CAR-T cells in the peripheral blood of Sec-MesoCAR-T group than that of MesoCAR-T group. This work demonstrated that the PD-L1 antibody secreted by Sec-MesoCAR-T cells relieved the immunosuppressive effect of pancreatic cancer on CAR-T cells and improved the anti-tumor activity of CAR-T cells, which has a good guiding significance for the clinical application of CAR-T cells in treating solid tumors.