Nucleoside transporters and human organic cation transporter 1 determine the cellular handling of DNA‐methyltransferase inhibitors

Abstract

BACKGROUND AND PURPOSEInhibitors of DNA methyltransferases (DNMTs), such as azacytidine, decitabine and zebularine, are used for the epigenetic treatment of cancer. Their action may depend upon their translocation across the plasma membrane. The aim of this study was to identify transporter proteins contributing to DNMT inhibitor action. EXPERIMENTAL APPROACHDrug interactions with selected hCNT and hENT proteins were studied in transiently transfected HeLa and MDCK cells. Interaction with human organic cation transporters (hOCTs) was assessed in transiently transfected HeLa cells and Xenopus laevis oocytes. KEY RESULTSZebularine uptake was mediated by hCNT1, hCNT3 and hENT2. Decitabine interacted with but was not translocated by any nucleoside transporter (NT) type. hCNT expression at the apical domain of MDCK cells promoted net vectorial flux of zebularine. Neither hOCT1 nor hOCT2 transported decitabine, but both were involved in the efflux of zebularine, suggesting these proteins act as efflux transporters. hOCT1 polymorphic variants, known to alter function, decreased zebularine efflux. CONCLUSIONS AND IMPLICATIONSThis study highlights the influence of human NTs and hOCTs on the pharmacokinetics and pharmacodynamics of selected DNMT inhibitors. As hOCTs may also behave as efflux transporters, they could contribute either to chemoresistance or to chemosensitivity, depending upon the nature of the drug or combination of drugs being used in cancer therapy.

Nucleoside transporter proteins as biomarkers of drug responsiveness and drug targets

“…As expected, purine-based nucleoside analogs such as fludarabine, cladribine, and clofarabine are substrates for hENT1, hENT2, hCNT3, and hCNT2 ( Lang et al, 2001 ; Molina-Arcas et al, 2005 ; King et al, 2006 ; Owen et al, 2006 ; Errasti-Murugarren and Pastor-Anglada, 2010 ). Conversely, pyrimidine analogs such as gemcitabine, cytarabine, and azacytidine are transported by hCNT1 in addition to hENT1, hENT2, and hCNT3 ( Mackey et al, 1999 ; Smith et al, 2004 ; Clarke et al, 2006 ; Endo et al, 2007 ; Errasti-Murugarren et al, 2007 ; Errasti-Murugarren and Pastor-Anglada, 2010 ; Arimany-Nardi et al, 2014 ). Nucleobases, such as 5-fluorouracil and 6-MP have also been reported to interact with hENT1 and hENT2 proteins, although their affinity constants are within the mM range ( Yao et al, 2011 ).…”

Development and in vitro evaluations of new decitabine nanocarriers for the treatment of acute myeloid leukemia

“…32 LNCs could thus facilitate the translocation of decitabine across the cellular membrane, which is generally carried out by nucleoside transporters, such as hENT1. 26,37,38 Thus, both the pathways could be used: free-drug through hENT 1 transport and decitabine-loaded THP-T80-LNCs through the endocytosis pathway. This property was also demonstrated, in various cancer cell lines, with a lipophilic-gemcitabine derivate loaded in solid lipid nanoparticles.…”

Nucleoside transporters in PET imaging of proliferating cancer cells using 3ꞌ-deoxy-3ꞌ-[18F]fluoro-L-thymidine

“…hENT4, also known as PMAT, is uniquely selective for adenosine and also transports a variety of organic cations [16][17][18][19][20]. Some nucleosidederived drugs can also interact with and be translocated by members of the SLC22 gene family, which include organic anion transporters (OATs), organic cation transporters (OCTs) and organic carnitine and zwitterion transporters (OCTNs) [9,[21][22][23][24][25].…”