Abstract
Background: We hypothesized that Sirtuin 1 (SIRT1) might attenuate the Warburg effect in tumor cells by modulating hypoxia-induced factor-1 alpha (HIF-1α) expression. This study aimed to explore the role and the underlying mechanism of SIRT1 in protecting the mitochondrial functions in hepatocellular carcinoma (HCC) cells. Methods: Quantitative real-time PCR and western blot analysis were conducted to determine gene expression in HCC cells. Co-immunoprecipitation (co-IP), chromatin immunoprecipitation (ChIP), and luciferase reporter assays were performed to examine DNA-protein interactions. Colony formation and MTT assays were carried out to explore the role of SIRT1 in HCC cell proliferation in vitro. PLC5 and Huh7 tumor xenografts were generated in mice to investigate the role of SIRT1–HIF-1α signaling in HCC development in vivo. Results: In different HCC cell lines, overexpression of SIRT1 promoted oxidative phosphorylation-associated gene expressions, ATP production, cell proliferation, and apoptotic protein expression while attenuating VEGF expression. In mice, overexpression of SIRT1 resulted in significant reductions in the weights of PLC5 and Huh7 tumor xenografts. Knockdown of SIRT1 exhibited opposite effects. Mechanistically, overexpression of SIRT1 promoted HIF-1α deacetylation, VHL-mediated HIF-1α degradation, and AMPK expression. Furthermore, SIRT1 interfered with the HIF-1α–c-Myc interaction to stimulate the transcription of a mitochondrial biogenesis enhancer mitochondrial transcription factor A (TFAM). Overexpression of HIF-1α completely reversed the effects of SIRT1.Conclusions: SIRT1 protects the mitochondria of HCC cells via suppressing HIF-1α expression, suggesting that SIRT1 may exert antitumor activity in HCC by reducing the Warburg effect.