| 1. |
- Ahlin, Gustav, 1977-, et al.
(författare)
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Endogenous Gene and Protein Expression of Drug Transporting Proteins in Cell Lines Routinely used in Drug Discovery Programs
- 2009
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Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 37:12, s. 2275-2283
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Tidskriftsartikel (refereegranskat)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, HEK293) and leukaemia cell lines used to study drug resistance by ABC-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 PCR was used, while monospecific polyclonal antibodies were generated and used to investigate protein expression by immunohistochemistry. Thirty-six transporters were studied for gene expression and nine 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 leukaemia cell lines (K562, HL-60) and Saos-2 also had low endogenous transporter expression, while 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. Importantly, the monocarboxylic acid transporting protein MCT1 was significantly expressed in all, and functional in most of the cell lines, indicating that MCT1 may be a confounding factor when the transport of small anionic drugs is investigated.
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| 2. |
- Hayeshi, Rose, et al.
(författare)
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Comparison of drug transporter gene expression and functionality in Caco-2 cells from 10 different laboratories
- 2008
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 35:5, s. 383-396
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Tidskriftsartikel (refereegranskat)abstract
- Caco-2 cells, widely used to study carrier mediated uptake and efflux mechanisms, are known to have different properties when cultured under different conditions. In this study, Caco-2 cells from 10 different laboratories were compared in terms of mRNA expression levels of 72 drug and nutrient transporters, and 17 other target genes, including drug metabolising enzymes, using real-time PCR. The rank order of the top five expressed genes was: HPT1>GLUT3>GLUT5>GST1A>OATP-B. Rank correlation showed that for most of the samples, the gene ranking was not significantly different. Functionality of transporters and the permeability of passive transport markers metoprolol (transcellular) and atenolol (paracellular) were also compared. MDR1 and PepT1 function was investigated using talinolol and Gly-Sar transport, respectively. Sulfobromophthalein (BSP) was used as a marker for MRP2 and OATP-B functionality. Atenolol permeability was more variable across laboratories than metoprolol permeability. Talinolol efflux was observed by all the laboratories, whereas only five laboratories observed significant apical uptake of Gly-Sar. Three laboratories observed significant efflux of BSP. MDR1 expression significantly correlated to the efflux ratio and net active efflux of talinolol. PepT1 mRNA levels showed significant correlation to the uptake ratio and net active uptake of Gly-Sar. MRP2 and OATP-B showed no correlation to BSP transport parameters. Heterogeneity in transporter activity may thus be due to differences in transporter expression as shown for PepT1 and MDR1 which in turn is determined by the culture conditions. Absolute expression of genes was variable indicating that small differences in culture conditions have a significant impact on gene expression, although the overall expression patterns were similar.
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| 3. |
- Hilgendorf, Constanze, et al.
(författare)
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Expression of thirty-six drug transporter genes in human intestine, liver, kidney, and organotypic cell lines
- 2007
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Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 35:8, s. 1333-1340
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Tidskriftsartikel (refereegranskat)abstract
- This study was designed to quantitatively assess the mRNA expression of 36 important drug transporters in human jejunum, colon, liver, and kidney. Expression of these transporters in human organs was compared with expression in commonly used cell lines (Caco-2, HepG2, and Caki-1) originating from these organs to assess their value as in vitro transporter system models, and was also compared with data obtained from the literature on expression in rat tissues to assess species differences. Transporters that were highly expressed in the intestine included HPT1, PEPT1, BCRP, MRP2, and MDR1, whereas, in the liver, OCT1, MRP2, OATP-C, NTCP and BSEP were the main transporters. In the kidney, OAT1 was expressed at the highest levels, followed by OAT3, OAT4, MCT5, MDR1, MRP2, OCT2, and OCTN2. The best agreement between human tissue and the representative cell line was observed for human jejunum and Caco-2 cells. Expression in liver and kidney ortholog cell lines was not correlated with that in the associated tissue. Comparisons with rat transporter gene expression revealed significant species differences. Our results allowed a comprehensive quantitative comparison of drug transporter expression in human intestine, liver, and kidney. We suggest that it would be beneficial for predictive pharmacokinetic research to focus on the most highly expressed transporters. We hope that our comparison of rat and human tissue will help to explain the observed species differences in in vivo models, increase understanding of the impact of active transport processes on pharmacokinetics and distribution, and improve the quality of predictions from animal studies to humans.
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