Construction of PD1/CD28 Fusion Receptor Enhances Anti-Tumor Ability of c-Met CAR-T in Gastric Cancer

Background: Chimeric antigen receptor (CAR) T cell is a promising method in cancer immunotherapy but faces many challenges in solid tumors. One of the major problem was immunosuppression cased by PD-1. Methods: The expression of c-Met in GC was analyzed from TCGA datasets, GC tissues and  cell lines. The c-Met CAR was a second generation CAR with 4-1BB, cMet-PD1/CD28 CAR was c-Met CAR adding PD1/CD28 fusion receptor. In vitro, we measured the changes of different subgroups, phenotypes and PD-1 expression in CAR-T cells. We detected the secretion levels of different cytokines and the killing ability of CAR-Ts. In vivo, we established a xenograft GC model and observed the anti-tumor effect and off-target toxicity of different CAR-Ts. Findings: The expression of c-Met was increased in GC. CD3+CD8+ T cells and CD62L+CCR7+ central memory T cells (TCM) were increased in two CAR-Ts. The stimulation of target cells could promote the expression of PD-1 in c-Met CAR-T. Compared with Mock T (blank control), the secretion of cytokines as IFN-γ, TNF-α, IL-6, IL-10 secreted by two CAR-Ts were increased, the killing ability to c-Met positive GC cells were enhanced. The PD1/CD28 fusion receptor could further enhance the killing ability especially the long-term anti-tumor effect of c-Met CAR-T and reduce the release level of IL-6. CAR-Ts target c-Met had no obvious off-target toxicity to normal organs. Interpretation: The PD1/CD28 fusion receptor could further enhance the anti-tumor ability of c-Met CAR-T, and provides a promising design strategy to improve the efficacy of CAR-T in GC. Funding Statement: This study was supported by National Natural Science Foundation of China (31770537), Key Research and Development Project of Gansu Science and Technology Plan (18YF1WA113), Special Research Project of Lanzhou University Serving the Economic and Social Development of Gansu Province (054000282) Declaration of Interests: The authors declared they have no conflict of interest. Ethics Approval Statement: Approval of the Ethics Committee of Lanzhou University Second Hospital and informed consent of patients. Animal experiments were approved by the Institutional Animal Care and Use Committee of Lanzhou University Second Hospital, comply with the animal welfare.