Abstract
The multidrug resistance-associated protein (MRP) mediates the cellular excretion of many drugs, glutathione S-conjugates (GS-X) of lipophilic xenobiotics and endogenous cysteinyl leukotrienes. Increased MRP levels in tumor cells can cause multidrug resistance (MDR) by decreasing the intracellular drug concentration. The physiological role or roles of MRP remain ill-defined, however. We have generated MRP-deficient mice by using embryonic stem cell technology. Mice homozygous for the mrp mutant allele, mrp-/-, are viable and fertile, but their response to an inflammatory stimulus is impaired. We attribute this defect to a decreased secretion of leukotriene C4 (LTC4) from leukotriene-synthesizing cells. Moreover, the mrp-/- mice are hypersensitive to the anticancer drug etoposide. The phenotype of mrp-/- mice is consistent with a role for MRP as the main LTC4-exporter in leukotriene-synthesizing cells, and as an important drug exporter in drug-sensitive cells. Our results suggest that this ubiquitous GS-X pump is dispensable in mice, making treatment of MDR with MRP-specific reversal agents potentially feasible.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP-Binding Cassette Transporters / genetics
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ATP-Binding Cassette Transporters / physiology*
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Adult
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Animals
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Antineoplastic Agents / adverse effects
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Antineoplastic Agents / pharmacokinetics
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Antineoplastic Agents / therapeutic use*
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Antineoplastic Agents, Phytogenic / adverse effects
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Antineoplastic Agents, Phytogenic / pharmacokinetics
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Bone Marrow Cells / drug effects
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Bone Marrow Cells / metabolism
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Carrier Proteins / physiology
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Drug Resistance, Multiple / physiology*
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Drug Resistance, Neoplasm
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Etoposide / adverse effects
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Etoposide / pharmacokinetics
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Humans
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Inflammation / chemically induced
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Inflammation / immunology*
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Leukotriene C4 / metabolism
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Membrane Transport Proteins
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Mice
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Mice, Knockout
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Multidrug Resistance-Associated Proteins
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Neoplasm Proteins / physiology*
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Neoplasms, Experimental / drug therapy*
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Neoplasms, Experimental / immunology
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Tumor Cells, Cultured
Substances
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ATP-Binding Cassette Transporters
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Antineoplastic Agents
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Antineoplastic Agents, Phytogenic
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Carrier Proteins
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Membrane Transport Proteins
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Multidrug Resistance-Associated Proteins
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Neoplasm Proteins
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glutathione transporter
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Leukotriene C4
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Etoposide