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Transport of 7-Ethyl-10-hydroxycamptothecin (SN-38) by Breast Cancer Resistance Protein ABCG2 in Human Lung Cancer Cells

https://doi.org/10.1006/bbrc.2001.5850Get rights and content

Abstract

Overexpression of breast cancer resistance protein (BCRP) ABCG2 reportedly confers cancer cell resistance to camptothecin-based anticancer drugs, such as topotecan and 7-ethyl-10-hydroxycamptothecin (SN-38: the active metabolite of irinotecan). We have recently shown that SN-38-selected PC-6/SN2-5H human lung carcinoma cells overexpressed BCRP with the reduced intracellular accumulation of SN-38 and SN-38-glucuronide (S. Kawabata et al., Biochem. Biophys. Res. Commun. 280, 1216–1223, 2001). In the present study, we have examined whether BCRP transports SN-38 and/or SN-38-glucuronide in vitro, by using plasma membrane vesicles from the parental PC-6 and resistant PC-6/SN2-5H cells, where SN-38 and SN-38-glucuronide accumulation in membrane vesicles was measured by HPLC. Both SN-38 and SN-38-glucuronide were ATP-dependently transported into membrane vesicles prepared from PC-6/SN2-5H cells, whereas no transport activity was observed in membrane vesicles from PC-6 cells. The kinetic parameters of the transport observed in PC-6/SN2-5H vesicles were Km = 4.0 μM, Vmax = 714 pmol/mg/min for SN-38 and Km = 26 μM, Vmax = 833 pmol/mg/min for SN-38-glucuronide. These findings suggest that BCRP expressed in PC-6/SN2-5H cells transports both SN-38 and SN-38-glucuronide with a higher affinity toward SN-38.

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  • Cited by (0)

    1

    The first and second authors contributed equally to this study.

    2

    To whom correspondence and reprint requests should be addressed at Second Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan. Fax: +81-(95)-849-7285. E-mail: [email protected].

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