NCF4 and neoplasm: As shown in Figure 6(a), high levels of NCF1, NCF2, and NCF4 mRNA expression had a significantly negative correlation with tumor purity (NCF1, r = −0.284, p < 0.001; NCF2, r = −0.241, p < 0.001; and NCF4, r = −0.357, p < 0.001) in KIRC.