SLC44A4 and nonpapillary renal cell carcinoma: After the difference analysis using the “limma” package, we found that the expression levels of SLC22A6, SLC22A7, SLC22A13, SLC25A4, SLC34A1, and SLC44A4 in ccRCC were significantly decreased (P < 0.01, as shown in Figures 9(a) and 9(b)), and the difference was statistically significant.