This Article Full Text Full Text (PDF) Supplementary Material Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Peklak-Scott, C. Articles by Morrow, C. S. PubMed PubMed Citation Articles by Peklak-Scott, C. Articles by Morrow, C. S.

Research Articles: Therapeutics, Targets, and Development

Role of glutathione S-transferase P1-1 in the cellular detoxification of cisplatin

Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina

Requests for reprints: Charles S. Morrow, Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157. Phone: 336-713-7218; Fax: 336-716-7161. E-mail: cmorrow{at}wfubmc.edu

Abstract

Cells expressing elevated levels of allelic variants of human glutathione S-transferase P1 (GSTP1) and/or efflux transporters, MRP1 or MRP2, were used to evaluate the role of GSTP1-1 in cisplatin resistance. These studies revealed that GSTP1-1 confers low-level resistance (1.4- to 1.7-fold) to cisplatin-induced cytotoxicity in MCF7 cells. However, expression of MRP1 (MCF7 cells) or MRP2 (HepG2 cells) failed to augment or potentiate GSTP1-1-mediated resistance in either cell line. To understand the mechanism by which variants of GSTP1-1 confer resistance to cisplatin, their relative abilities to catalyze conjugation of cisplatin with glutathione were examined. Enzymes encoded by all three alleles tested, GSTP1a (I₁₀₄A₁₁₃), GSTP1b (V₁₀₄A₁₁₃), and GSTP1c (V₁₀₄V₁₁₃), increased the formation rate of the mono-platinum/glutathione derivative of cisplatin with relative catalytic activities of 1.0 (GSTP1a-1a variant) and 1.8 to 1.9 (GSTP1b-1b and GSTP1c-1c variants). Although these data are consistent with the idea that very low level resistance to cisplatin may be conferred by GSTP1-1-mediated cisplatin/glutathione conjugation, two observations indicate that such catalysis plays a minor role in the protection from cisplatin toxicity. First, the rates of GSTP1-1-mediated conjugation are extremely slow (1.7-2.6 h^–1 at 25°C). Second, despite an 80% to 90% increase in catalysis of cisplatin conjugation by GSTP1b-1b or GSTP1c-1c over GSTP1a-1a, we observed no discernable differences in relative resistances conferred by these alternative variants when expressed in MCF7 cells. We conclude that high-level cisplatin resistance attributed to GSTP1-1 in other studies is not likely due to catalysis of cisplatin conjugation but rather must be explained by other mechanisms, which may include GSTP1-mediated modulation of signaling pathways. [Mol Cancer Ther 2008;7(10):3247–55]

Grant support: NIH grant CA 70338.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Supplementary material for this article is available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

² Goto et al. (18) examined the kinetics of GSTP1-1-catalyzed conjugation of cisplatin with GSH at 37°C reporting a V_max of 4.9 nmol/min/mg and a K_m for cisplatin of 0.23 mmol/L. Although not reported as such, a k_cat of 14 h^-1 can be calculated from their data assuming the molar mass of GSTP1-1 is 46,682 g/mol.

Received 3/14/08; revised 6/ 9/08; accepted 7/13/08.