ABSTRACT
Objective To observe the influence of sirtinol,a silent information regulator 1(SIRT1)inhibitor,in the cell proliferation, cell cycle progression and the expression levels of positive regulator proteins of the cell cycle including Cyclin D1,CDK4 and pRb in prostate cancer DU145 cells,and to explore the possible mechanism of SIRT1 in occurrence of prostagte cancer.Methods The DU145 cells at logarithmic growth phase were cultured in vitro and divided into control group(DMSO)and different doses (10,25,50μmol·L-1 )of sirtinol groups.The inhibitory rate of growth of DU145 cells was detected with MTT method,the SIRT1 mRNA and protein expression levels were determined by RT-PCR and Western blotting method, and the cell cycle was measured by flow cytometry.The Cyclin D1,CDK4 and pRb protein expression levels were examined by Western blotting method. Results Compared with control group, the inhibitory rates of growth of the DU145 cells in different doses of sirtinol groups were increased markedly in a dose-dependent manner(P0.05).Conclusion SIRT1 inhibition by sirtinol can inhibit the cell growth of prostate cancer DU145 cells in a dose-dependent manner and arrest the cell cycle progression,and its mechanism may be related to decreasing the CyclinD1 and pRb protein expressions.
ABSTRACT
OBJECTIVE: To investigate the combined effects of cisplatin and the histone deacetylase (HDAC) inhibitors suberoylanilide hydroxamic acid (SAHA) or sirtinol on HeLa cells and assess the mechanism underlying HDAC inhibitor-cisplatin synergy. METHODS: The antineoplastic actions of cisplatin, SAHA and sirtinol, alone and in combination, were evaluated using the tetrazolium dye-based MTT cell proliferation assay, DAPI nuclear staining and cytotoxicity analysis. RESULTS: Exposure to cisplatin, SAHA or sirtinol alone induced a dose-dependent reduction in HeLa cell viability. Combined treatment with cisplatin and SAHA or sirtinol was significantly more cytotoxic than cisplatin alone. Individually, cisplatin, SAHA and sirtinol activated caspase-3 and induced apoptosis, but the effects of combined treatment were greater. Importantly, both HDAC inhibitors dose-dependently inhibited the expression of the antiapoptotic proteins Bcl-2 and x-linked inhibitor of apoptosis protein (XIAP). CONCLUSION: The combination of cisplatin and SAHA or sirtinol had synergistic effect on the HeLa cell viability. This potentiation of cisplatin activity was associated with HDAC inhibitor-mediated down-regulation of Bcl-2 and XIAP. These may result from the relaxation of chromatin by these HDAC inhibitors that increase cisplatin sensitivity by enhancing the accessibility of DNA to cisplatin and transcriptional regulators.