Cytotoxic effect of s-petasin and iso-s-petasin on the proliferation of human prostate cancer cells

Background: Petasin (Petasides hybridus) is a perennial shrub that is found in Europe as well as parts of Asia and North America and is being used to treat hypertension, tumors and asthma. In a previous study, we reported that petasin possesses biological effects including inhibition of testosterone production and the release of corticosterone from rat zona fasciculata-reticularis cells, and anti-proliferative effect on human T24 bladder carcinoma cells.Materials and Methods: In the present study, we assessed the effects of S-petasin and iso-S-petasin on the growth and proliferation of two hormone-independent DU145 and PC3 and one hormone-dependent LNCaP prostate cancer cell line at concentrations of 10-7-10-5 mol/l. The cell proliferation index, cell number index, expression of caspases and apoptosis-associated proteins and cell morphology were measured.Results: S-Petasin and iso-Spetasin reduced the viable cell number and increased the numbers of apoptotic cells in the tested cell lines in a dosedependent manner. Western blot analysis revealed that Spetasin and iso-S-petasin reduced the protein levels of procaspase 3, 8, and 9 and cleaved poly(ADP-ribose) polymerase (PARP) in all tested prostate cancer cell lines, and reduced that of procaspase 7 in LNCaP and PC3 cells. At the same time, S-petasin and iso-S-petasin increased mitochondrial membrane permeability and cytochrome c release from mitochondria to the cytosol via reducing the ratio of BCL2/BAX in DU145 and PC3 cells, and upregulating the levels of p53 in DU145 cells but downregulating it in PC3 cells.Conclusion: These results indicate that S-petasin and iso-S-petasin induce apoptosis via the activation of mitochondria-related pathways in prostate cancer cells, suggesting S-petasin and iso-S-petasin could be potential anticancer agents.