IGFBP1 and nonpapillary renal cell carcinoma: Clustering with k = 4 for the cluster with poorest survival revealed the same 10 hub genes: APOB, IGFBP1, CP, ENAM, MFI2, CHRDL1, IL6, TF, FGA, FGG. Interestingly, among the hub genes of Cluster 1 was the SERPINA5 gene, one of the most decreased in ccRCC (Fig. 2d).