CD28 and neoplasm: Blocking PD-1 through specific antibody, shRNA, or dominant negative receptor restored the function of Mesothelin-targeting CD28 CAR T cells, and CAR-T cells with constitutive anti-PD-1 secretion were more functional, expandable, and efficient in tumor eradication than parental CAR-T cells in a human lung carcinoma xenograft mouse model 39, 40.