title: Localization of tamoxifen in human breast cancer tumors by MALDI mass spectrometry imaging.
abstract: BACKGROUND
  Tamoxifen is used in endocrine treatment of breast cancer to inhibit estrogen signaling. A set of stratified ER-positive and ER-negative tumor sections was subjected to manual deposition of tamoxifen solution in order to investigate its spatial distribution upon exposure to interaction within thin tissue sections.
  
  
  METHODS
  The localization of tamoxifen in tumor sections was assessed by matrix assisted laser deposition/ionization mass spectrometry imaging. The images of extracted ion maps were analyzed for comparison of signal intensity distributions.
  
  
  RESULTS
  The precursor ion of tamoxifen (m/z 372.233) displayed heterogeneous signal intensity distributions in histological compartments of tumor tissue sections. The levels of tamoxifen in tumor cells compared with stroma were higher in ER-positive tissues, whereas ER-negative tissue sections showed lower signal intensities in tumor cells.
  
  
  CONCLUSIONS
  The experimental model was successfully applied on frozen tumor samples allowing for differentiation between ER groups based on distribution of tamoxifen.
authors.affiliation: Department of Biomedical Engineering, Clinical Protein Science and Imaging, Lund University, BMC D13, 221 84, Lund, Sweden. Akos.Vegvari@bme.lth.se.
authors.forename: Ákos
authors.identifier: http://orcid.org/0000-0002-1287-0906
authors.initials: Á
authors.lastname: Végvári
authors.affiliation: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Shavkunov
authors.affiliation: Department of Biomedical Engineering, Clinical Protein Science and Imaging, Lund University, BMC D13, 221 84, Lund, Sweden.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Fehniger
authors.affiliation: Department of Oncology and Pathology, Clinical Science, Lund University, Lund, Sweden.
authors.forename: Dorthe
authors.initials: D
authors.lastname: Grabau
authors.affiliation: Department of Oncology and Pathology, Clinical Science, Lund University, Lund, Sweden.|Department of Surgery, Skåne University Hospital, Lund, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Niméus
authors.affiliation: Department of Biomedical Engineering, Clinical Protein Science and Imaging, Lund University, BMC D13, 221 84, Lund, Sweden.
authors.forename: György
authors.initials: G
authors.lastname: Marko-Varga
keywords: Drug localization; Drug quantification; Estrogen receptor stratification; Human breast cancer; MALDI-mass spectrometry imaging; Tamoxifen treatment