title: Uptake of the anthracycline pirarubicin into mouse M5076 ovarian sarcoma cells via a sodium-dependent nucleoside transport system.
abstract: OBJECTIVE
  We have previously demonstrated that the cytotoxicity of anthracyclines, pirarubicin (THP) and doxorubicin (DOX), is partially dominated by their intracellular amounts, which depend on the uptake efficacy of transporter(s). To clarify their transport mechanism, we examined whether or not Na+/nucleoside cotransporter (CNT) is involved in the uptake of THP by M5076 cells.
  
  
  METHODS
  Expression of the CNT isoforms was determined by reverse-transcription PCR. We used two cell lines, intact M5076 and CNT2-transfected Cos-7 cells, to characterize the uptake of THP and [3H]uridine.
  
  
  RESULTS
  The mRNA for CNT2, but not that for CNT1 or CNT3, was expressed in M5076 cells, and [3H]uridine uptake by the cells required a Na+ gradient as a driving force. THP uptake by M5076 cells depended on a Na+ gradient, and furthermore, formycin B and AZT had cis-inhibitory and trans-stimulatory effects on the uptake. The efflux of [3H]uridine from M5076 cells was stimulated by the addition of THP extracellularly, which constituted definite evidence of CNT-mediated uptake of THP. However, THP uptake by CNT2 transfectant was almost the same as that by mock cells, indicating that an unidentified CNT isoform contributes to THP uptake by M5076 cells, this being supported by the differences in transport characteristics of [3H]uridine between M5076 and CNT2-transfected cells.
  
  
  CONCLUSIONS
  THP is partially taken up into M5076 cells via a novel Na+-dependent transport system common to nucleosides.
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto, 607-8414, Japan. nagai@mb.kyoto-phu.ac.jp
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Nagai
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nagasawa
authors.forename: Sadaki
authors.initials: S
authors.lastname: Fujimoto
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism*; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000378:metabolism*; D005260:Female; D051379:Mice; D033703:Nucleoside Transport Proteins / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D014529:Uridine
chemical_list: D000903:Antibiotics, Antineoplastic; D033703:Nucleoside Transport Proteins; D004317:Doxorubicin; D012964:Sodium; C027260:pirarubicin; D014529:Uridine