CTLA4 and nonpapillary renal cell carcinoma: In TCGA dataset, CTLA4 was highly expressed in tumor tissues (N = 494) compared to normal tissues (N = 68, p < 0.001), and the paired test also confirmed that CTLA4 was highly expressed in ccRCC (N = 68, p < 0.001) (Fig. 1a, b).