title: (125)I-Labelled 2-Iodoestrone-3-sulfate: synthesis, characterization and OATP mediated transport studies in hormone dependent and independent breast cancer cells.
abstract: BACKGROUND
  Organic Anion Transporting Polypeptides (OATP) are a family of membrane associated transporters that facilitate estrone-3-sulphate (E3S) uptake by hormone dependent, post-menopausal breast cancers. We have established E3S as a potential ligand for targeting hormone dependent breast cancer cells, and in this study sought to prepare and investigate radioiodinated E3S as a tool to study the OATP system.
  
  
  METHODS
  2- and 4-Iodoestrone-3-sulfates were prepared from estrone via aromatic iodination followed by a rapid and high yielding sulfation procedure. The resulting isomers were separated by preparative HPLC and verified by (1)H NMR and analytical HPLC. Transport studies of 2- and 4-[(125)I]-E3S were conducted in hormone dependent (i.e. MCF-7) and hormone independent (i.e. MDA-MB-231) breast cancer cells in the presence or absence of the specific transport inhibitor, bromosulfophthalein (BSP). Cellular localization of OATP1A2, OATP2B1, OATP3A1 and OATP4A1 were determined by immunofluorescence analysis using anti-Na(+)/K(+) ATPase-α (1:100 dilution) and DAPI as plasma membrane and nuclear markers, respectively.
  
  
  RESULTS
  Significantly (p<0.01) higher total accumulation of 2-[(125)I]-E3S was observed in hormone dependent MCF-7 as compared to hormone independent MDA-MB-231 breast cancer cells. In contrast 4-[(125)I]-E3S did not show cellular accumulation in either case. The efficiency of 2-[(125)I]-E3S transport (expressed as a ratio of Vmax/Km) was 2.4 times greater in the MCF-7 as compared to the MDA-MB-231 breast cancer cells. OATP1A2, OATP3A1 and OATP4A1 expression was localized in plasma membranes of MCF-7 and MDA-MB-231 cells confirming the functional role of these transporters in radioiodinated E3S cellular uptake.
  
  
  CONCLUSIONS
  An efficient method for the preparation of 2- and 4-[(125)I]-E3S was developed and where the former demonstrated potential as an in vitro probe for the OATP system. The new E3S probe can be used to study the OATP system and as a platform to create radiopharmaceuticals for imaging breast cancer.
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nilasha
authors.initials: N
authors.lastname: Banerjee
authors.affiliation: Centre for Probe Development and Commercialization (CPDC), McMaster University, Hamilton, Ontario, Canada.
authors.forename: T Robert
authors.initials: TR
authors.lastname: Wu
authors.affiliation: Centre for Probe Development and Commercialization (CPDC), McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Chio
authors.affiliation: Centre for Probe Development and Commercialization (CPDC), McMaster University, Hamilton, Ontario, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Kelly
authors.affiliation: Centre for Probe Development and Commercialization (CPDC), McMaster University, Hamilton, Ontario, Canada.
authors.forename: Karin A
authors.initials: KA
authors.lastname: Stephenson
authors.affiliation: Centre for Probe Development and Commercialization (CPDC), McMaster University, Hamilton, Ontario, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Forbes
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: Allen
authors.affiliation: Centre for Probe Development and Commercialization (CPDC), McMaster University, Hamilton, Ontario, Canada; Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada. Electronic address: valliant@mcmaster.ca.
authors.forename: John F
authors.initials: JF
authors.lastname: Valliant
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada. Electronic address: r.bendayan@utoronto.ca.
authors.forename: Reina
authors.initials: R
authors.lastname: Bendayan
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology*; D045744:Cell Line, Tumor; D060326:Chemistry Techniques, Synthetic; D004970:Estrone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D027361:Organic Anion Transporters / Q000378:metabolism*; D049268:Positron-Emission Tomography; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D006728:Hormones; D007457:Iodine Radioisotopes; D027361:Organic Anion Transporters; D020033:Protein Isoforms; D004970:Estrone; C017296:estrone sulfate
keywords: Breast cancer; Estrone-3-sulfate; Iodine-125; Organic anion transporting polypeptide