Objective: To explore the antiprostate cancer effects of Celastrol on prostate cancer cells' proliferation, apoptosis, and cell cycle distribution, as well as the correlation to the regulation of hERG.
Methods: DU145 cells were treated with various concentrations of Celastrol (0.25-16.0 μmol/L) for 0-72 hours. MTT assay was used to evaluate the inhibition effect of Celastrol on the growth of DU145 cells. Cell apoptosis was detected through both Annexin-V FITC/PI double-labeled cytometry and Hoechst 33258. Cell cycle regulation was examined by a propidium iodide method. Western blot and RT-PCR technologies were applied to assess the expression level of hERG in DU145 cells.
Results: Celastrol presented striking growth inhibition and apoptosis induction potency on DU145 cells in vitro in a time- and dose-dependent manner. The IC50 value of Celastrol for 24 hours was 2.349 ± 0.213 μmol/L. Moreover, Celastrol induced DU145 cell apoptosis in a cell cycle-dependent manner, which means Celastrol could arrest DU145 cells in G0/G1 phase; accordingly, cells in S phase decreased gradually and no obvious changes were found in G2/M phase cells. Through transmission electron microscope, apoptotic bodies containing nuclear fragments were found in Celastrol-treated DU145 cells. Overexpression of hERG channel was found in DU145 cells, while Celastrol could downregulate it at both protein and mRNA level in a dose-dependent manner (P < 0.01).
Conclusions: Celastrol exhibits its antiprostate cancer effects partially through the downregulation of the expression level of hERG channel in DU145 cells, suggesting that Celastrol may be a potential agent against prostate cancer with a mechanism of blocking the hERG channel.