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ABCG2 confers resistance to indolocarbazole compounds by ATP-dependent transport
Rinako Nakagawa1, Yoshikazu Hara, Hiroharu Arakawa
1Banyu Tsukuba Research Institute in Collaboration with Merck Research Laboratories, 3 Okubo, Ibaraki 300-2611, Japan.
Abstract:
The ABC half-transporter, ABCG2, is known to confer resistance to chemotherapeutic agents including indolocarbazole derivatives. MCF7 cells were introduced by either wild type ABCG2 (ABCG2-482R) or mutant ABCG2 (-482T), whose amino acid at position 482 is substituted to threonine from arginine, and their cross-resistance pattern was analyzed. Although this amino acid substitution seems to affect cross-resistance patterns, both 482T- and 482R-transfectants showed strong resistance to indolocarbazoles, confirming that ABCG2 confers resistance to them. For further characterization of ABCG2-mediated transport, we investigated indolocarbazole compound A (Fig. 1) excretion in cell-free system. Compound A was actively transported in membrane vesicles prepared from one of the 482T- transfectants and its uptake was supported by hydrolysis of various nucleoside triphosphates. This transport was inhibited completely by the other indolocarbazole compound, but not by mitoxantrone, implying that the binding site of mitoxantrone or the transport mechanisms for mitoxantrone is different from those of indolocarbazoles. These results showed that ABCG2 confers resistance to indolocarbazoles by transporting them in an energy-dependent manner.
Insights
The ATP-binding cassette transporter ABCG2 confers resistance to indolocarbazoles. This transporter actively moves indolocarbazoles in an energy-dependent manner, impacting chemotherapy drug resistance.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- The ATP-binding cassette (ABC) transporter ABCG2 is implicated in multidrug resistance.
- ABCG2 confers resistance to various chemotherapeutic agents, including indolocarbazole derivatives.
Purpose of the Study:
- To investigate the role of ABCG2 in conferring resistance to indolocarbazoles.
- To characterize the transport mechanism of indolocarbazoles by ABCG2.
Main Methods:
- MCF7 cells were transfected with wild-type ABCG2 (ABCG2-482R) or a mutant (ABCG2-482T).
- Cross-resistance patterns were analyzed.
- Indolocarbazole compound A excretion was studied in a cell-free system using membrane vesicles.
Main Results:
- Both wild-type and mutant ABCG2-expressing cells exhibited strong resistance to indolocarbazoles.
- Indolocarbazole compound A was actively transported by ABCG2 in an energy-dependent manner.
- Transport was inhibited by another indolocarbazole but not by mitoxantrone, suggesting distinct binding sites or transport mechanisms.
Conclusions:
- ABCG2 confers resistance to indolocarbazoles.
- ABCG2 mediates the energy-dependent transport of indolocarbazoles.
- The transport mechanism for indolocarbazoles by ABCG2 differs from that of mitoxantrone.