NTN4 and nonpapillary renal cell carcinoma: The expression of NTN5 and NTNG2, among the six Netrin family members, was significantly upregulated in ccRCC tissues; NTN3 was downregulated in ccRCC samples, but no significant difference was observed in 72 paired samples included in the TCGA database; the other three genes (NTN1, NTN4, and NTNG1) were significantly downregulated in ccRCC tissues (Figure 2A,B).