Title

Kinetics of Cisplatin Binding to Cellular DNA and Modulations by Thiol-Blocking Agents and Thiol Drugs

Document Type

Article

Date

11-9-2001

Keywords

article; atomic absorption spectrometry; cancer cell; controlled study; drug binding; drug DNA binding; drug transport; high performance liquid chromatography; human; human cell; mononuclear cell; ovary cancer; priority journal; 2 (3 aminopropylamino)ethanethiol; cell DNA; cisplatin; mesna; n ethylmaleimide; platinum; thiol derivative; thiol reagent

Disciplines

Chemistry

Description/Abstract

DNA platination by cisplatin (CDDP) was investigated in peripheral blood mononuclear cells and ovarian cancer cells using atomic absorption spectroscopy. Plots showing the amount of platinum (Pt) bound to DNA versus the molar concentration of cisplatin in the incubation medium ([CDDP]) were nonlinear. For [CDDP] < about 5 μM, the amount of Pt bound to DNA increased slowly with added drug. However, for larger [CDDP], the slope of the plot increased significantly. To study the role of thiols in affecting cisplatin binding to DNA, cells were treated with N-ethylmaleimide, which modifies thiol groups, rendering them incapable of binding cisplatin. Analysis using high-pressure liquid chromatography showed that ∼99% of cellular glutathione was modified by Nethylmaleimide. A plot of the amount of Pt bound to DNA versus [CDDP] for thiol-blocked cells is linear, with a slope similar to that at unblocked cells at high [CDDP]. Neither S-2-(3 aminopropylamino)ethanethiol (WR-1065) nor mesna, when added at clinically achievable concentrations (i.e., < ∼300 μM), affected DNA platination. However, D]NA platination was totally abolished by millimolar concentrations of the drug thiols (∼1.25 mM WR-1065 or ∼5 mM mesna). Thus, the data show that endogenous thiols intercept cellular cisplatin, but this mechanism is less important at high [CDDP]. Moreover, therapeutic concentrations of drug thiols do not significantly affect DNA platination. A simple model that reproduces the experimental results of the amount of cisplatin binding to DNA as a function of [CDDP], time, and thiol content is proposed. The model takes into account passage of cisplatin and thiols through the cell membrane, binding of cisplatin to cellular thiols, and platination of DNA.

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First author and SU authors listed for additional authors see the article.

Copyright 2002 Drug Metabolism and Disposition. This article may be downloaded for personal use only. Any other use requires prior permission of the author and Drug Metabolism and Disposition.

The article may be found at http://dmd.aspetjournals.org/content/30/2/183.full.pdf

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