CA9 and renal carcinoma: Compared with Ctrl-CAR-T (E:T = 2:1), CAIX-CAR-T presented the highest cytotoxicity efficacy for CAIX-positive renal cancer cells OSRC-2 and 786O but a least cytotoxicity for CAIX-low expression ACHN, in which CAIX-CAR-T with high E:T rate (5:1) could cause significant cytotoxicity (Figure 2C).