Abstract
The mammalian copper transporter 1 (CTR1) is responsible for the uptake of copper from the extracellular space. In this study, we used an isogenic pair of CTR1(+/+) and CTR1(-/-) mouse embryo fibroblasts to examine the contribution of CTR1 to the influx of cisplatin (DDP), carboplatin (CBDCA), oxaliplatin (L-OHP), and transplatin. Exposure to DDP triggered the rapid degradation of CTR1, suggesting that its contribution to influx was likely to be on the initial phase of drug entry. Loss of CTR1 decreased the initial binding of DDP to cells and reduced influx measured over the first 5 min of drug exposure by 81%. Loss of CTR1 almost completely eliminated the initial influx of CBDCA and reduced the initial uptake of L-OHP by 68% but had no effect on the influx of transplatin. Loss of CTR1 rendered cells resistant to even high concentrations of DDP when measured in vitro, and re-expression of CTR1 in the CTR1(-/-) cells restored both DDP uptake and cytotoxicity. The growth of CTR1(-/-) tumor xenografts in which CTR1 levels were restored by infection with a lentivirus expressing wild-type CTR1 was reduced by a single maximum tolerated dose of DDP in vivo, whereas the CTR1(-/-) xenografts failed to respond at all. We conclude that CTR1 mediates the initial influx of DDP, CBDCA, and L-OHP and is a major determinant of responsiveness to DDP both in vitro and in vivo.
Footnotes
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This work was supported by the National Institutes of Health National Cancer Institute [Grants CA78648 and 5T32-CA121938]. The production of 64Cu at Washington University School of Medicine was supported by the National Institutes of Health [Grant R24-CA86307].
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Portions of this work were presented at the 2008 Annual Meeting of the American Association for Cancer Research: Larson C, Chung N, and Howell S (2008) Role of mammalian copper transporter (CTR1) in the cellular accumulation of cisplatin, carboplatin and oxaliplatin. Proc Am Assoc Cancer Res49:4771.
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ABBREVIATIONS: CTR1, mammalian copper transporter 1; CBDCA, carboplatin; DDP, cisplatin; L-OHP, oxaliplatin; PBS, phosphate-buffered saline; ddH2O, double-distilled H2O; qRT-PCR, qualitative reverse transcriptase-polymerase chain reaction; BBR3464, [{trans-PtCl(NH3)2}2μ-(trans-Pt(NH3)2(H2N(CH2)6NH2)2)]4+.
- Received October 1, 2008.
- Accepted November 7, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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