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  • Title: Bimodal effects of 1R,2R-diaminocyclohexane(trans-diacetato)(dichloro)platinum(IV) on cell cycle checkpoints.
    Author: Kuang J, He G, Huang Z, Khokhar AR, Siddik ZH.
    Journal: Clin Cancer Res; 2001 Nov; 7(11):3629-39. PubMed ID: 11705886.
    Abstract:
    1R,2R-Diaminocyclohexane(trans-diacetato)(dichloro)-platinum(IV) (DACH-acetato-Pt) is a novel platinum-based agent that is highly effective against cisplatin-resistant ovarian tumor cells. To probe its cellular mechanism, the effects of DACH-acetato-Pt (0-6.4 microM) on cell cycle checkpoints were examined using the ovarian cancer A2780 cell line as the model system. We found that DACH-acetato-Pt at > or =0.2 microM dramatically inhibited cell growth and induced cell death. At concentrations < or =0.6 microM (low effective concentrations), DACH-acetato-Pt specifically induced G(1) phase arrest by selectively inhibiting cyclin-dependent kinase 4 (Cdk4) and Cdk2 activities. The Cdc2 activity, which regulates G(2)-M phase progression, was unaffected by the drug at these concentrations. At concentrations >0.6 microM (high effective concentrations), DACH-acetato-Pt first transiently inhibited S-phase progression and then blocked cell cycle progression at both G(1) and G(2) phases. These cell cycle effects were associated with sequential inhibitions of Cdk2/cyclin A activity, Cdk4 and Cdk2 activities, and Cdc2 kinase activity. Following the cell cycle effects, both the low and high effective concentrations of DACH-acetato-Pt induced cell death through apoptosis. These results indicate that DACH-acetato-Pt activates multiple cell cycle checkpoints in a bimodal manner and suggest that the cell cycle effects demonstrated in these studies may be linked to its ability to induce apoptosis.
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