Abstract
PURPOSE: D,L-Sulforaphane (SFN) is a promising chemopreventive agent with in vivo efficacy against prostate cancer in experimental rodents. This study was undertaken to determine the role of vimentin and plasminogen activator inhibitor-1 (PAI-1) in anticancer effects of SFN. METHODS: Effect of SFN on levels of different proteins was determined by Western blotting or immunofluorescence microscopy. RNA interference of vimentin and PAI-1 was achieved by transient transfection. Apoptosis was quantified by flow cytometry. Transwell chambers were used to determine cell migration. RESULTS: Exposure of PC-3 and DU145 human prostate cancer cells to SFN resulted in induction of vimentin protein, which was accompanied by down-regulation of E-cadherin protein expression. The SFN-mediated induction of vimentin was also observed in a normal human prostate epithelial cell line. RNA interference of vimentin did not have any appreciable effect on early or late apoptosis resulting from SFN exposure. On the other hand, SFN-mediated inhibition of PC-3 and DU145 cell migration was significantly augmented by knockdown of the vimentin protein. Knockdown of vimentin itself was inhibitory against cell migration. The SFN-treated cells also exhibited induction of PAI-1, which is an endogenous inhibitor of urokinase-type plasminogen activator system. Similar to vimentin, PAI-1 knockdown resulted in a modest augmentation of PC-3 cell migration inhibition by SFN. Tumors from SFN-treated transgenic adenocarcinoma of mouse prostate mice showed a 1.7-fold increase in vimentin protein level compared with control tumors. CONCLUSION: The present study indicates that vimentin and PAI-1 inductions confer modest protection against SFN-mediated inhibition of prostate cancer cell migration.