Abstract
Multidrug resistance (MDR), a challenge in treating childhood acute myeloid leukemia (AML), is frequently associated with decreased drug accumulation caused by multidrug transporter MDR1. Doxorubicin, an important anti-AML drug, is a known MDR1 substrate and inducer. Its cytostatic efficacy is thus limited by MDR1 overexpression. A recent study demonstrated cyclooxygenase-2-dependent, prostaglandin E2 (PGE2)-mediated regulation of mdr1b expression in primary rat hepatocyte cultures. Cyclooxygenase-2 expression is increased in several malignancies and considered a negative prognostic factor. Our study focused on cyclooxygenase system's impact on drug-induced MDR1 overexpression in AML cells. As a prerequisite, coexpression of MDR1 and cyclooxygenase-2 mRNA in HL-60 cells and primary AML blasts was demonstrated by Northern blot. Interestingly, incubation of AML cells with doxorubicin not only induced functionally active MDR1 overexpression but also mediated increased cyclooxygenase-2 mRNA and protein expressions with subsequent PGE2 release (determined by flow cytometry, rhodamine123 efflux assay, reverse transcription-polymerase chain reaction, and enzyme-linked immunosorbent assay). After preincubation and subsequent parallel treatment with the cyclooxygenase-2-preferential inhibitor meloxicam, doxorubicin-induced MDR1 overexpression and function were reduced (maximally at 0.1-0.5 μM meloxicam), whereas cytostatic efficacy of doxorubicin in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assays was significantly increased by up to 78 (HL-60) and 30% (AML blasts) after 72 h of doxorubicin treatment. In HL-60 cells, meloxicam-dependent effect on doxorubicin cytotoxicity was neutralized by PGE2 preincubation. In conclusion, the cyclooxygenase system, especially the cyclooxygenase-2 isoform, might be involved in regulating doxorubicin-induced MDR1 overexpression in AML cells, with PGE2 seeming to be a mediating factor. Cyclooxygenase inhibitors thus bear promise to overcome MDR in AML and improve therapy.
Footnotes
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↵1 These authors contributed equally to this study.
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This study was supported by grants from the José Carreras Foundation (DJCLS SP 01/02) (to U.P.) and the “Forschungsförderprogramm 2000” provided by the Faculty of Medicine, University of Goettingen (to C.Z.). Parts of this study were presented in abstract form at the 43rd Spring Meeting of the German Society of Experimental and Clinical Pharmacology and Toxicology, Mainz, Germany, March 12-14, 2002; at the 44th Annual Meeting of the American Society of Hematology, Philadelphia, PA, December 6-10, 2002; and at the 44th Spring Meeting of the German Society of Experimental and Clinical Pharmacology and Toxicology, Mainz, Germany, March 17-22, 2003.
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doi:10.1124/jpet.104.071571.
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ABBREVIATIONS: AML, acute myeloid leukemia; MDR, multidrug resistance; COX, cyclooxygenase; FCS, fetal calf serum; PGE2, prostaglandin E2; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; PCR, polymerase chain reaction; FITC, fluorescein isothiocyanate; Rho123, rhodamine 123; DOX, doxorubicin; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide; ELISA, enzyme-linked immunosorbent assay; SAS, Statistical Analysis System; NSAID, nonsteroidal anti-inflammatory drug; NF-κB, nuclear factor-κB; AP-1, activator protein-1; EP, prostaglandin E receptor.
- Received May 18, 2004.
- Accepted October 19, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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