Nature Medicine
7, 584 - 590 (2001)
doi:10.1038/87912
The orphan nuclear receptor SXR coordinately regulates drug metabolism and effluxTimothy W. Synold1, 4, Isabelle Dussault2, 4
& Barry Marc Forman2, 31
Department of Medical Oncology and Therapeutics Research, The Beckman Research Institute, City of Hope National Medical Center, Duarte, California, USA
2
Department of Molecular Medicine, The Beckman Research Institute, City of Hope National Medical Center, Duarte, California, USA
3
The Gonda Diabetes & Genetic Research Center, The Beckman Research Institute, City of Hope National Medical Center, Duarte, California, USA
4
I.D. and T.W.S. contributed equally to this study.
Correspondence should be addressed to Barry Marc Forman bmforman@earthlink.netCytochrome P450 3A4 is an important mediator of drug catabolism that can be regulated by the steroid and xenobiotic receptor (SXR). We show here that SXR also regulates drug efflux by activating expression of the gene MDR1, which encodes the protein P-glycoprotein (ABCB1). Paclitaxel (Taxol), a commonly used chemotherapeutic agent, activated SXR and enhanced P-glycoprotein−mediated drug clearance. In contrast, docetaxel (Taxotere), a closely related antineoplastic agent, did not activate SXR and displayed superior pharmacokinetic properties. Docetaxel's silent properties reflect its inability to displace transcriptional corepressors from SXR. We also found that ET-743, a potent antineoplastic agent, suppressed MDR1 transcription by acting as an inhibitor of SXR. These findings demonstrate how the molecular activities of SXR can be manipulated to control drug clearance.
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