According to TCGA data from http://gepia.cancer-pku.cn/, we firstly compared the HHLA2 expression at the mRNA expression level between human ccRCC tissues and adjacent normal tissues, and higher expression of HHLA2 was found in human ccRCC tissues compared with the adjacent normal tissues (Fig. 1a, P < 0.05). This evidence concerns the gene HHLA2 and nonpapillary renal cell carcinoma.