PTTG1 and nonpapillary renal cell carcinoma: Fourthly, we conducted expression analysis to these 30 mRNAs separately in stage, grade, distant metastasis, ccRCC, and normal tissues and eventually obtained six hub mRNAs (BUB1B, CCNB2, KIF18B, PLK1, PTTG1, and TOP2A) that were not only upregulated in the samples of distant metastasis but were also positively significantly associated with higher grades in patients with ccRCC (Figure 5).