We have shown previously that
diallyl trisulfide (DATS), a constituent of processed garlic, inhibits proliferation of PC-3 and DU145 human
prostate cancer cells by causing G(2)-M phase cell cycle arrest in association with inhibition of
cyclin-dependent kinase 1 activity and hyperphosphorylation of Cdc25C at Ser(216). Here, we report that DATS-treated PC-3 and DU145 cells are also arrested in mitosis as judged by microscopy following staining with anti-
alpha-tubulin antibody and
4',6-diamidino-2-phenylindole and flow cytometric analysis of Ser(10) phosphorylation of
histone H3. The DATS treatment caused activation of
checkpoint kinase 1 and
checkpoint kinase 2, which are intermediaries of DNA damage checkpoints and implicated in Ser(216) phosphorylation of Cdc25C. The
diallyl trisulfide-induced Ser(216) phosphorylation of Cdc25C as well as mitotic arrest were significantly attenuated by knockdown of check-point
kinase 1
protein in both PC-3 and DU145 cells. On the other hand, depletion of
checkpoint kinase 2 protein did not have any appreciable effect on G(2) or M phase arrest or Cdc25C phosphorylation caused by
diallyl trisulfide. The lack of a role of
checkpoint kinase 2 in
diallyl trisulfide-induced phosphorylation of Cdc25C or G(2)-M phase cell cycle arrest was confirmed using HCT-15 cells stably transfected with phosphorylation-deficient mutant (T68A mutant) of
checkpoint kinase 2. In conclusion, the results of the present study suggest existence of a checkpoint
kinase 1-dependent mechanism for
diallyl trisulfide-induced mitotic arrest in human
prostate cancer cells.