| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Experimental Therapeutics, Molecular Targets, and Chemical Biology |
1 Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel; Departments of 2 Rheumatology and 3 Medical Oncology, VU University Medical Center, Amsterdam, the Netherlands; and 4 Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
Requests for reprints: Yehuda G. Assaraf, Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel. Phone: 972-4-829-3744; Fax: 972-4-822-5213; E-mail: assaraf{at}tx.technion.ac.il.
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 µmol/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-
-glutamate synthetase activity. These results provide the first evidence that the G482-ABCG2 mutation confers high-level resistance to various hydrophilic antifolates.
This article has been cited by other articles:
![]() |
E. E. Bram, Y. Adar, N. Mesika, M. Sabisz, A. Skladanowski, and Y. G. Assaraf Structural Determinants of Imidazoacridinones Facilitating Antitumor Activity Are Crucial for Substrate Recognition by ABCG2 Mol. Pharmacol., May 1, 2009; 75(5): 1149 - 1159. [Abstract] [Full Text] [PDF] |
||||
![]() |
C.-l. Dai, A. K. Tiwari, C.-P. Wu, X.-d. Su, S.-R. Wang, D.-g. Liu, C. R. Ashby Jr., Y. Huang, R. W. Robey, Y.-j. Liang, et al. Lapatinib (Tykerb, GW572016) Reverses Multidrug Resistance in Cancer Cells by Inhibiting the Activity of ATP-Binding Cassette Subfamily B Member 1 and G Member 2 Cancer Res., October 1, 2008; 68(19): 7905 - 7914. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Breedveld, D. Pluim, G. Cipriani, F. Dahlhaus, M. A. J. van Eijndhoven, C. J. F. de Wolf, A. Kuil, J. H. Beijnen, G. L. Scheffer, G. Jansen, et al. The Effect of Low pH on Breast Cancer Resistance Protein (ABCG2)-Mediated Transport of Methotrexate, 7-Hydroxymethotrexate, Methotrexate Diglutamate, Folic Acid, Mitoxantrone, Topotecan, and Resveratrol in In Vitro Drug Transport Models Mol. Pharmacol., January 1, 2007; 71(1): 240 - 249. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |