Diallyl disulfide selectively causes checkpoint kinase-1 mediated G2/M arrest in human MGC803 gastric cancer cell line

Previous studies have shown that diallyl disulfide (DADS), a naturally occurring anticancer agent in garlic, arrested human gastric cancer cells (MGC803) in the G(2)/M phase of the cell cycle. Due to the importance of cell cycle redistribution in DADS-mediated anticarcinogenic effects, we investigated the role of checkpoint kinases (Chkl and Chk2) during DADS-induced cell cycle arrest. In the present study, the northern blot analysis showed that mRNA expression of for Chkl and Chk2 was unchanged. Notably, DADS induced the accumulation of phosphorylated Chkl, but not of Chk24 activated phospho-ATR (ATM-RAD3 -related gene), and dowregulated CDC25C and cyclin B1 expression. Furthermore, CDC25C was immunoprecipitated by anti-Chkl but not antiChk2. Results of the overexpression and knockdown studies, showed that Chkl but not Chk2 regulated the DADS-induced G(2)/M arrest of MGC803 cells. The overexpression of Chkl resulted in significantly increased DADS-induced G(2)/M arrest, increased DADS-induced. Chkl phosphorylation and inhibited CDC25C expression. Knockdown of Chkl reduced DADS-induced G2/M arrest and blocked the DADS-induced inhibition of CDC25C and cyclin B1 expression. These results suggested that Chkl is important in DADS-induced cell cycle G(2)/M arrest in the human MGC803 gastric cancer cell line. Furthermore, the DADS-induced G(2)/M checkpoint response is mediated by Chkl signaling through ATR/Chkl/CDC25C/ cyclin Bl.