| Objective: To study the impact of nucleus accumbens-1(NAC1) expression on glycolysis and survival in cancer cell and the molecular mechanism involved.Methods:NAC1 has been observed to be up-regulated in human ovarian cancer,and to play an important role in progression and recurrence of ovarian cancer. In this study, we investigated the regulatory role of NAC1 in glycolysis and the effect of the NAC1-mediated glycolysis on cancer cell survival. Cell biology, molecular biology, and pharmacology approaches and methods were used in this study.Results: We demonstrated:1) NAC1 is a critical regulator of cancer cell survival under hypoxic condition. Silencing of NAC1 leads to increases in Annexin V staining amounts of the cleaved caspase-3 and cleaved PARP, and a decline in cell number when the cells were subjected to hypoxia.2) NAC1 is a novel regulator of glycolysis.NAC1 possesses a promotive role in glycolysis in ovarian cancer both in vivo and vitro. Depletion of NAC1 leads to an increase in the concentration of glucose in the culture medium, a decrease in the level of intercellular lactate, and declines in the m RNA and protein levels of glucose transporter 1(GLUT1) and lactate dehydrogenase A(LDHA), which are among the key players in glycolysis. Expression of NAC1 also enhances the glycolysis in a mouse tumor model, as indicated by an increase in the uptake of 18F-FDG,an indicator of glucose absorption level and tumor development. 3) The impact of NAC1 on glycolysis is mediated by its interaction with HDAC4, thereby protecting HIF-1α from acetylation and ubiquitin-proteasomal degradation of this transcription factor. We showed in co-immunoprecipitation and GST-pulldown assays that the association of NAC1 with HDAC4 protects HDAC4 from phosphorylation at ser246 and increases its stability, and this in turn inhibits the acetylation of HIF-1αand the ubiquitination-mediated degradation of HIF-1α.Conclusion: The effect of NAC1 on glycolysis in cancer cells is mediated through the NAC1-HDAC4-HIF1α pathway. These new findings reveal the molecular and cellular functions of NAC1 in cancer metabolism, and provide an evidence for NAC1 as a potential target for cancer prevention and treatment. |
