SFRP1 and nonpapillary renal cell carcinoma: Indeed, comparing ccRCC samples to NT tissue samples, KCNJ1 showed a decrease of its expression levels to -133.8 (p-value = 2.94E-05) (Figure 2A), SFRP1 resulted down-regulated with a fold change of -55.1 (p-value = 1.74E-08) (Figure 2B), while TCF21 expression dropped -16.8 times (p-value = 6.70E-11) (Figure 2C).