Abstract
The aim of this study was to investigate the gene and protein expression profiles of important drug-transporting proteins in human cell lines commonly used for studies of drug transport mechanisms. Human cell lines used to transiently or stably express single transporters [HeLa, human embryonic kidney (HEK) 293] and leukemia cell lines used to study drug resistance by ATP-binding cassette transporters (HL-60, K562) were investigated and compared with organotypic cell lines (HepG2, Saos-2, Caco-2, and Caco-2 TC7). For gene expression studies, real-time polymerase chain reaction was used, whereas monospecific polyclonal antibodies were generated and used to investigate protein expression by immunohistochemistry. Thirty-six transporters were studied for gene expression, and nine were studied for protein expression. The antibodies were validated using expression patterns in human tissues. Finally, the function of one ubiquitously expressed transporter, MCT1/SLC16A1, was investigated using [14C]lactic acid as a substrate. In general, the adherent cell lines (HeLa, HEK293) displayed low transporter expression, and the expression patterns were barely affected by transfection. The leukemia cell lines (K562, HL-60) and Saos-2 also had low endogenous transporter expression, whereas the organotypic cell lines (HepG2 and Caco-2) showed higher expression of some transporters. Comparison of gene and protein expression profiles gave poor correlations, but better agreement was obtained for antibodies with a good validation score, indicating that antibody quality was a significant variable. It is noteworthy that the monocarboxylic acid-transporting protein MCT1 was significantly expressed in all and was functional in most of the cell lines, indicating that MCT1 may be a confounding factor when the transport of small anionic drugs is investigated.
Footnotes
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This work was supported in part by AstraZeneca; the Swedish Research Council [Grant 9478]; the Knut and Alice Wallenberg Foundation; the Swedish Fund for Research Without Animal Experiments; and the Swedish Board of Agriculture.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.109.028654
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↵ The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
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- ABC
- ATP-binding cassette
- MRP
- multidrug resistance protein
- HEK
- human embryonic kidney
- BCRP
- breast cancer resistance protein
- SLC
- solute carrier transporter
- HPR
- human proteome resource
- msAb
- monospecific polyclonal antibody
- RT-PCR
- real-time polymerase chain reaction
- IHC
- immunohistochemistry
- PrEST
- protein epitope signature tag
- IBAT
- ileal bile acid transporter
- HBSS
- Hanks' balanced salt solution.
- Received June 6, 2009.
- Accepted September 2, 2009.
- Copyright © 2009 by The American Society for Pharmacology and Experimental Therapeutics
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