SIRT4 is an independent prognostic factor in bladder cancer and inhibits bladder cancer growth by suppressing autophagy

Background: Nucleosome-localized sirtuin 4 (SIRT4) was found to function as an oncogene and tumor suppressor genes in different tumors, respectively. However, the clinical significance of SIRT4 in bladder urothelial carcinoma (BLCA) has not been assessed, as well as the analysis of the function of SIRT4 in BLCA. Methods In this study, we assessed the levels of SIRT4 protein in BLCA tissues and its association with clinicopathological parameters and overall survival time of BLCA patients by immunohistochemical staining of tissue microarrays containing 59 BLCA patients. Then, we constructed BLCA cell lines (T24) with overexpression or interference SIRT4 by lentiviral infection. The effects of SIRT4 on the proliferation, migration and invasive ability and of T24 cells were investigated using cell counting kit-8 (CCK-8) assays, wound healing assays, migration and invasion assays. Moreover, we also investigated the effect of SIRT4 on cell cycle and apoptosis of T24 cells. Mechanistically, we explored the relationship between SIRT4 and autophagy and its role in the inhibition of BLCA. Results We found by immunohistochemistry that SIRT4 protein levels were reduced in BLCA and that lower SIRT4 levels were associated with larger tumor volumes, later T-staging and later AJCC staging in BLCA patients and were an independent prognostic factor in BLCA patients. Overexpression with SIRT4 significantly inhibited the proliferative viability, scratch healing capacity, migratory capacity, and invasive capacity of T24 cells while interfering of SIRT4 had the opposite effect. Moreover, overexpression with SIRT4 significantly inhibited cell cycle and increased the apoptosis rate of T24 cells. Mechanistically, SIRT4 inhibits BLCA growth by suppressing autophagic flow. Conclusions Our study suggests that SIRT4 is an independent prognostic factor for BLCA, and that SIRT4 function as tumor suppressor role in BLCA. This suggests a potential target for SIRT4 in the diagnosis and treatment of BLCA.