Research Paper
Subject Category: Pharmacokinetics, drug metabolism, toxicology
British Journal of Pharmacology (2007) 152, 815–824; doi:10.1038/sj.bjp.0707467; published online 1 October 2007
The multidrug transporter ABCG2 (BCRP) is inhibited by plant-derived cannabinoids
M L Holland1, D T T Lau2, J D Allen2 and J C Arnold1
- 1The Discipline of Pharmacology, The University of Sydney, Sydney, New South Wales, Australia
- 2The Centenary Institute of Cancer Medicine and Cell Biology, Sydney, New South Wales, Australia
Correspondence: Dr JC Arnold, The Discipline of Pharmacology, Bosch Institute of Medical Sciences, Bosch Building 1B D05, The University of Sydney, Sydney, New South Wales 2006, Australia. E-mail: arnie@med.usyd.edu.au
Received 13 August 2007; Accepted 23 August 2007; Published online 1 October 2007.
Abstract
Background and purpose:
Cannabinoids are used therapeutically for the palliation of the adverse side effects associated with cancer chemotherapy. However, cannabinoids also inhibit both the activity and expression of the multidrug transporter, P-glycoprotein in vitro. Here we address the interaction of cannabinol (CBN), cannabidiol (CBD) and 
9-tetrahydrocannabinol (THC) with the related multidrug transporter, ABCG2.
Experimental approach:
Cannabinoid inhibition of Abcg2/ABCG2 was assessed using flow cytometric analysis of substrate accumulation and ATPase activity assays. The cytotoxicity and chemosensitization by cannabinoids was determined with cell viability assays. Expression of cannabinoid and vanilloid receptors was assessed using reverse transcriptase polymerase chain reaction, and cannabinoid modulation of ABCG2 expression was examined using immunoblotting.
Key results:
CBN, CBD and THC increased the intracellular accumulation of the Abcg2/ABCG2 substrate, mitoxantrone, in an over-expressing cell line. The THC metabolite, (-)-11-nor-9-carboxy-9-THC was much less potent. The plant cannabinoids inhibited both basal and substrate stimulated ATPase activity of human ABCG2. Cannabinoid cytotoxicity occurred in the absence of known cannabinoid cell surface receptors, and only at concentrations higher than those required for Abcg2/ABCG2 inhibition. Sub-toxic concentrations of the cannabinoids resensitized the overexpressing cell line to the cytotoxic effect of Abcg2/ABCG2 substrates, mitoxantrone and topotecan. This occurred in the absence of any effect on ABCG2 expression.
Conclusions and implications:
Cannabinoids are novel Abcg2/ABCG2 inhibitors, reversing the Abcg2-mediated multidrug-resistant phenotype in vitro. This finding may have implications for the co-administration of cannabinoids with pharmaceuticals that are ABCG2 substrates.
Keywords:
cannabinoids, multidrug transporters, ABCG2, BCRP, chemotherapy, multidrug resistance, breast cancer resistance protein, 9-tetrahydrocannabinol, cannabis, cannabidiol
Abbreviations:
BCRP, breast cancer resistance protein; CBD, cannabidiol; CBN, cannabinol; Dnase, deoxyribonuclease; MDR, multiple drug resistance; MEF, mouse embryonic fibroblasts; P-gp, p-glycoprotein; THC, 9-tetrahydrocannabinol; THC-A, (-)-11-nor-9-carboxy-9-THC
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