They began by assessing the effectiveness of inhibiting immune checkpoints with anti-CTLA-4 antibodies or anti-PD-L1 antibodies in six different syngeneic mouse tumor models (CT26, RENCA, 4T1, B16F10 AP-3, LL/2, and MC38) and observed that only two models responded to the anti-CTLA-4 treatment, CT26 (a mouse colon carcinoma model), and RENCA (a mouse renal cell carcinoma model), as measured by decreases in tumor volume [64]. Here, CTLA4 is linked to renal cell carcinoma.