CELL INTELLIGENCE · 肿瘤细胞治疗研究

The carbonic anhydrase IX (CAIX) expression occurs in most cases of clear cell renal cell carcinoma (ccRCC). This tumor type is characterized by an immunosuppressive microenvironment, where approximately one-fourth of patients overexpress the programmed cell death ligand-1 (PD-L1), significantly increasing their risk of death. Herein, we present a secondary effect of CAIX inhibition using monoclonal antibodies (mAbs) and CAR T cells, leading to PD-L1 downregulation in ccRCC and in vivo immune checkpoint blockade. We identified a positive correlation between CAIX and PD-L1 expression in ccRCC cell lines using in silico RNA-seq data analysis, prompting us to perform fluorescence-activated cell sorting of SKRC52 ccRCC cell subpopulations based on their positive or negative expression of CAIX and PD-L1. After two weeks in culture, the cell population selected to be negative for CAIX and positive for PD-L1 became negative for CAIX and PD-L1. To explore the phenomenon, CAIX blockade was performed using two anti-CAIX monoclonal antibodies (mAbs) in multiple doses in two CAIX+ PD-L1+ clear cell renal cell carcinoma (ccRCC) cell lines. The expression of CAIX and PD-L1 decreased after treatment with the mAbs, and the PI3K/Akt signaling pathway is involved in this modulation. CAIX-targeted CAR T cells in vivo also reduced PD-L1 expression, resulting in superior CD3 infiltration and granzyme B expression, which decreased T cell exhaustion. Our findings demonstrate that CAIX-targeted immunotherapies can induce an indirect immune checkpoint blockade by PD-L1 downregulation.