ABSTRACT
Objective: Cell cycle has recently become more appealing as a new target of anti-carcinogen-ic agent. Diallyl disulfide (DADS) inhibits growth and induces call cycle G_2/M arrest in human gastric cancer BGC823 cells. Cell division cycle protein 25C (Cdc25C) and CyclinB1 expression are involved in G_2/M arrest.However, mechanisms of G_2/M arrest are not yet fully understood. The aim of this study was to elucidate the mechanism of cell cycle G_2/M arrest in human gastric cancer BGC823 cells induced by DADS. Methods: The expression of chk1 and Chk2 mRNA associated with cell cycle arrest of BGC823 cells after the induction with DADS for 1 or 2 days was detected by RT-PCR. The protein expression of cycle-related proteins ATM-RAD3-related gene (ATR), checkpoint kinase1 (Chk1), checkpoint kinase 2 (Chk2), P-ATR, P-Chk1 and P-Chk2 was measured by Western blot. Interaction between Chk1/2 and Cdc25C was analyzed by immuno-precipitation. Results: After the cells were treated with 15 mg/L DADS for 1 or 2 days, the expression of Chk1 and Chk2 mRNA was not significantly different from that in untreated cells (P>0.05). Western blot analysis showed that the expression of total Chk1 and Chk2 treated with 15 mg/L DADS was not significantly different from that in untreated cells. But phospho-chk1 showed a significant increase after stimulation with 15 mg/L DADS for 2h to 12h and continued to increase gradually as time went on (P<0.05). Phospho-Chk2 showed a eak expression and a weaker expression after stimulation with DADS, but the changes were not statistically significant (P>0.05). Addition of 15 mg/L DADS to BGC823 cells for 15 rain to 120 min resulted in an increase in phospho-ATR expression, whereas no changes were found in ATR expression (P<0.05). The Chk1 Ab in-creasingly precipitated Cdc25C in BGC823 cells treated with DADS (P<0.05). In contrast, Chk2 Ab failed to change precipitation with Cdc25C by DADS (P>0.05). Conclusion: Activation of chk1 was involved in cell cy-cle G_2/M arrest in BGC823 cells treated with DADS. Cell cycle G_2/M arrest by DADS is associated with phos-phorylation of several cell cycle regulatory proteins including ATR and Chk1 which regulate expression of Cdc25C.