Abstract
One of the many obstacles to effective drug treatment is the efflux transporter P-glycoprotein (P-gp), which can restrict the plasma and intracellular concentrations of numerous xenobiotics. Variable drug response to P-gp substrates suggests that genetic differences in ABCB1 may affect P-gp transport. The current study examined how ABCB1 variants alter the P-gp-mediated transport of probe substrates in vitro. Nonsynonymous ABCB1 variants and haplotypes with an allele frequency ≥2% were transiently expressed in HEK293T cells, and the transport of calcein acetoxymethyl ester and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY-FL)-paclitaxel was measured in the absence or presence of the P-gp inhibitor cyclosporin A. The A893S, A893T, and V1251I variants and the N21D/1236C>T/A893S/3435C>T haplotype altered intracellular accumulation compared with reference P-gp in a substrate-dependent manner. It is interesting that certain variants showed altered sensitivity to cyclosporin A inhibition that was also substrate-specific. These functional data demonstrate that nonsynonymous polymorphisms in ABCB1 may selectively alter P-gp transport and drug-drug interactions in a substrate- and inhibitor-dependent manner.
Footnotes
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This work was supported by National Institutes of Health Grant GM61390 and the Robert Black Charitable Foundation.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.135194.
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ABBREVIATIONS: P-gp, P-glycoprotein; SNP, single nucleotide polymorphism; FBS, fetal bovine serum; calcein-AM, calcein-acetoxymethyl ester; BODIPY-FL, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; APC, allophycocyanin; EMEM, Eagle's minimum essential medium; NBD, nucleotide binding domain; CsA, cyclosporin A; TMD, transmembrane domain; PBS, phosphate-buffered saline; TMD, transmembrane domain; FRT, Flp recombinase target.
- Received December 10, 2007.
- Accepted February 19, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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