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XB-ART-48107
Clin Cancer Res 2014 Feb 15;204:985-94. doi: 10.1158/1078-0432.CCR-13-1999.
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Cellular uptake of imatinib into leukemic cells is independent of human organic cation transporter 1 (OCT1).

Nies AT , Schaeffeler E , van der Kuip H , Cascorbi I , Bruhn O , Kneba M , Pott C , Hofmann U , Volk C , Hu S , Baker SD , Sparreboom A , Ruth P , Koepsell H , Schwab M .


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In addition to mutated BCR-ABL1 kinase, the organic cation transporter 1 (OCT1, encoded by SLC22A1) has been considered to contribute to imatinib resistance in patients with chronic myeloid leukemia (CML). As data are conflicting as to whether OCT1 transports imatinib and may serve as a clinical biomarker, we used a combination of different approaches including animal experiments to elucidate comprehensively the impact of OCT1 on cellular imatinib uptake. Transport of imatinib was studied using OCT1-expressing Xenopus oocytes, mammalian cell lines (HEK293, MDCK, V79) stably expressing OCT1, human leukemic cells, and Oct1-knockout mice. OCT1 mRNA and protein expression were analyzed in leukemic cells from patients with imatinib-naïve CML as well as in cell lines. Transport and inhibition studies showed that overexpression of functional OCT1 protein in Xenopus oocytes or mammalian cell lines did not lead to an increased cellular accumulation of imatinib. The CML cell lines (K562, Meg-01, LAMA84) and leukemic cells from patients expressed neither OCT1 mRNA nor protein as demonstrated by immunoblotting and immunofluorescence microscopy, yet they showed a considerable imatinib uptake. Oct1 deficiency in mice had no influence on plasma and hepatic imatinib concentrations. These data clearly demonstrate that cellular uptake of imatinib is independent of OCT1, and therefore OCT1 is apparently not a valid biomarker for imatinib resistance.

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Species referenced: Xenopus laevis
Genes referenced: abl1 bcr nat8.6 pou2f1

References [+] :
Bazeos, hOCT1 transcript levels and single nucleotide polymorphisms as predictive factors for response to imatinib in chronic myeloid leukemia. 2010, Pubmed