Purpose: Diallyl disulfide (DADS), an organosulfur compound in garlic, has been reported to be effective in inhibiting the growth of several human tumor cell lines. The aim of this study was to determine whether DADS induced growth
inhibition in
MCF-7 breast cancer cell lines and to understand the molecular mechanism by which DADS acts.
Methods: MCF-7 cell lines were incubated with various concentrations of DADS for various time intervals and the cytotoxicity was determined by MTT assay. We examined the changes of intracellular proteins related to apoptosis, such as
bcl-2,
bax
and PARP in cells treated with DADS. To study the expression level of bcl-2 and bax, which serve as modulators of apoptosis, we performed RT-PCR and western blot analysis.
Results: MCF-7 cells treated with DADS led to the suppression of viability and proliferation in both a time and concentration dependent manner. Microscopic observation revealed typical features of apoptosis in the DADS-treated cells,
further
verified in nuclear DAPI staining. Flow cyto-metry analysis with FITC-annexinV and propidium iodide (PI) demonstrated that the apoptotic cell population with AnnexinV+/PI- increased dramatically from ∼0.8% to ∼75% after 24h exposure to 500㎛
DADS
in
MCF-7 cells. Cell cycle analysis demonstrated that the number of apoptotic cells increased with the increasing time of the DADS treatment. Additionally, thermore, we investigated the effects of DADS on apoptosis related gene expression in MCF-7
cells.
PARP cleavage was markedly increased in the DADS treated cells with time. This result indicated that DADS induced the caspase-dependent apoptotic pathway. We also found down-regulation of bcl-2, however no significant change of Bax expression was
observed after DADS treatment.
Conclusion: Taken together, these results indicate that DADS induces apoptosis by activating a caspase pathway involving the activation of Bcl-2 but not of Bax. Our findings suggest chemotherapeutic potentials of DADS in human breast
cancer.
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