Histone deacetylase (HDAC) inhibitors are known to be used in molecular target theraphy for several malignant cancer. We previously reported that HDAC inhibitors induced apoptosis in human oral squamous cell carcinoma cells, Ca9-22. In the present study, we investigated the effect of the cyclic tetrapeptide class inhibitor, Ky-2, on signaling pathway in the induction of cell cycle arrest and apoptosis in myeloma cells.
Method:
Myeloma cells, HS-72, P3U1, and Bcl-2 overexpressed HS-72 cells were used in this study. Effect of HDAC inhibitors to cell viability was determined by WST-1 assay. Cell cycle was analyzed using flow cytometry. The expression of cell cycle regulatory proteins (p21, Rb and CDK4, 6) and the apoptosis associated proteins (caspase-9 and caspase-3) were examined by Western blot analysis. Hoechst’s staining was used to detect apoptotic cells.
Result:
The hyperacetylation of histone H3 and a decrease in the level of HDAC1 and HDAC2 were observed in Ky-2-treated myeloma cells. The cell proliferation of Ky-2-treated myeloma cells were significantly inhibited. Flow cytometer analysis revealed that Ky-2 treatment induced a G1 phase cell-cycle arrest and accumulation of a sub G1 phase in myeloma cells. Western blot analysis revealed that the expression of cell cycle-related protein, p21 and phosphorylated Rb, were upregulated in Ky-2-treated myeloma cells. In addition, Ky-2 enhanced the expression of caspase-9 and caspase-3 cleavage in western blotting analysis. However, Ky-2 treatment had no effect on the induction of apoptosis in Bcl-2overexpressed HS-72 cells.
Conclusion:
Our results showed that Ky-2 induced G1 cell cycle arrest through some regulatory proteins related to cell cycle in myeloma cells, and that the Ky-2 induced apoptosis in the dependent of caspase cascades.