SIRT4 and nonpapillary renal cell carcinoma: As shown in Fig. 1, the immunohistochemistry (IHC) staining data from the THPA database showed increased protein expression levels of SIRT1, SIRT2, SIRT3, SIRT6, and SIRT7, whereas the expression of SIRT4 and SIRT5 was significantly lower (particularly SIRT5), in ccRCC tissues.