title: Endogenous gene and protein expression of drug-transporting proteins in cell lines routinely used in drug discovery programs.
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 [(14)C]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.
authors.affiliation: Department of Pharmacy, Uppsala University, SE-751 23 Uppsala, Sweden.
authors.forename: Gustav
authors.initials: G
authors.lastname: Ahlin
authors.forename: Constanze
authors.initials: C
authors.lastname: Hilgendorf
authors.forename: Johan
authors.initials: J
authors.lastname: Karlsson
authors.forename: Cristina Al-Khalili
authors.initials: CA
authors.lastname: Szigyarto
authors.forename: Mathias
authors.initials: M
authors.lastname: Uhlén
authors.forename: Per
authors.initials: P
authors.lastname: Artursson
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001692:Biological Transport; D018938:Caco-2 Cells; D002448:Cell Adhesion; D055808:Drug Discovery / Q000379:methods*; D020869:Gene Expression Profiling; D018922:HL-60 Cells; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D007150:Immunohistochemistry; D020014:K562 Cells; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D040901:Proteomics; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000378:metabolism; D014162:Transfection; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D018528:ATP-Binding Cassette Transporters; D026901:Membrane Transport Proteins; D027501:Monocarboxylic Acid Transporters; D004364:Pharmaceutical Preparations; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1