Purpose: The present study was undertaken to gain insight into the molecular mechanism of G2/M phase cell cycle arrest resulting from treatment of DU145 cells with diallyl trisulfide (DATS), a promising cancer chemopreventive constituent of garlic.
Methods: Cell cycle distribution was determined by flow cytometry. Immunoblotting was performed to determine protein expression. Overexpression of wild-type or mutant Cdc25C was achieved by transient transfection. Nuclear and cytoplasmic localization of cyclin B1 and cyclin-dependent kinase 1 (cdk1) was studied by immunoblotting.
Results: Exposure of DU145 human prostate cancer cells to DATS resulted in concentration- and time-dependent accumulation of G2/M phase cells, which correlated with down-regulation as well as increased S216 phosphorylation of Cdc25C. Ectopic expression of wild-type or redox-insensitive mutants (C330S and C330S/C377S) or S216A mutant of Cdc25C failed to confer protection against DATS-induced G2/M phase arrest. The DATS-mediated G2/M phase cell cycle arrest was also independent of reduced complex formation between cdk1 and cyclin B1, but correlated with delayed nuclear translocation of cdk1.
Conclusion: The present study indicates that the DATS-mediated G2/M phase cell cycle arrest in DU145 cells results from differential kinetics of nuclear localization of cdk1 and cyclin B1.