CD28 and nonpapillary renal cell carcinoma: The lower PD-L1 and Ki67 expression observed in tumors from mice treated with anti-CAIX CD28 anti-PD-L1 IgG compared with the anti-CAIX 4-1BB anti-PD-L1 IgG CAR T cells may be explained by the superior cytotoxicity of PD-L1 positive ccRCC cells induced by the improvement of CD28-based anti-CAIX CAR T cells function by anti-PD-L1 IgG.