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ABCG2 harboring the Gly482 mutation confers high-level resistance to various hydrophilic antifolates.
- Source :
-
Cancer research [Cancer Res] 2005 Sep 15; Vol. 65 (18), pp. 8414-22. - Publication Year :
- 2005
-
Abstract
- ABCG2 is an ATP-binding cassette transporter that confers resistance to various chemotherapeutic agents. Recent studies have established that an Arg (wild-type) to Gly mutation at amino acid 482 in ABCG2 alters substrate specificity. Here, we explored the role of this G482 mutation in antifolate resistance using a clinically relevant 4-hour drug exposure. Stable transfectants overexpressing the mutant G482 transporter displayed 120-, 1,000-, and >6,250-fold resistance to the antifolates methotrexate, GW1843, and Tomudex, respectively, relative to parental human embryonic kidney cells. Moreover, although overexpressing equal transporter levels at the plasma membrane, G482-ABCG2 cells were 6-, 23-, and >521-fold more resistant to methotrexate, GW1843, and Tomudex, respectively, than R482-ABCG2 cells. In contrast, upon a continuous (72-hour) drug exposure, both the G482- and R482-ABCG2 cells lost almost all their antifolate resistance; this result was consistent with the inability of ABCG2 to extrude long-chain antifolate polyglutamates. Ko143, a specific and potent ABCG2 inhibitor reversed methotrexate resistance in both G482- and R482-ABCG2 cells. Consistently, whereas the pool of free methotrexate in parental human embryonic kidney cells was prominent after 4 hours of transport with 1 micromol/L [3H]methotrexate, in R482- and G482-ABCG2 cells, it was minimal. Furthermore, G482-ABCG2 cells contained marked decreases in the di- and triglutamate species of [3H]methotrexate at 4 hours of incubation with methotrexate and in the tetra- and pentaglutamates at 24 hours. These changes were not associated with any significant decrease in folylypoly-gamma-glutamate synthetase activity. These results provide the first evidence that the G482-ABCG2 mutation confers high-level resistance to various hydrophilic antifolates.
- Subjects :
- ATP Binding Cassette Transporter, Subfamily G, Member 2
ATP-Binding Cassette Transporters biosynthesis
Cell Line
Cell Membrane metabolism
Doxorubicin pharmacology
Drug Resistance, Neoplasm
Folic Acid Antagonists pharmacokinetics
Humans
Methotrexate analogs & derivatives
Methotrexate pharmacokinetics
Methotrexate pharmacology
Mutation
Neoplasm Proteins biosynthesis
Polyglutamic Acid analogs & derivatives
Polyglutamic Acid pharmacokinetics
Polyglutamic Acid pharmacology
Subcellular Fractions metabolism
Transfection
Tritium
ATP-Binding Cassette Transporters genetics
ATP-Binding Cassette Transporters metabolism
Folic Acid Antagonists pharmacology
Neoplasm Proteins genetics
Neoplasm Proteins metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0008-5472
- Volume :
- 65
- Issue :
- 18
- Database :
- MEDLINE
- Journal :
- Cancer research
- Publication Type :
- Academic Journal
- Accession number :
- 16166320
- Full Text :
- https://doi.org/10.1158/0008-5472.CAN-04-4547