SIRT4 and bladder transitional cell carcinoma: We first performed immunohistochemical staining of tissue microarrays containing 59 human BLCA tissues and 59 paraneoplastic nontumor bladder tissues, and we found that SIRT4 was mainly expressed in the cytoplasm (Fig. 1A) and that the staining level of SIRT4 was significantly lower in tumor tissues than in paraneoplastic nontumor bladder urothelial tissues (Fig. 1A, B).