title: Prospects of Targeting the Gastrin Releasing Peptide Receptor and Somatostatin Receptor 2 for Nuclear Imaging and Therapy in Metastatic Breast Cancer.
abstract: BACKGROUND
  The gastrin releasing peptide receptor (GRPR) and the somatostatin receptor 2 (SSTR2) are overexpressed on primary breast cancer (BC), making them ideal candidates for receptor-mediated nuclear imaging and therapy. The aim of this study was to determine whether these receptors are also suitable targets for metastatic BC.
  
  
  METHODS
  mRNA expression of human BC samples were studied by in vitro autoradiography and associated with radioligand binding. Next, GRPR and SSTR2 mRNA levels of 60 paired primary BCs and metastases from different sites were measured by quantitative reverse transcriptase polymerase chain reaction. Receptor mRNA expression levels were associated with clinico-pathological factors and expression levels of primary tumors and corresponding metastases were compared.
  
  
  RESULTS
  Binding of GRPR and SSTR radioligands to tumor tissue correlated significantly with receptor mRNA expression. High GRPR and SSTR2 mRNA levels were associated with estrogen receptor (ESR1)-positive tumors (p<0.001 for both receptors). There was no significant difference in GRPR mRNA expression of primary tumors versus paired metastases. Regarding SSTR2 mRNA expression, there was also no significant difference in the majority of cases, apart from liver and ovarian metastases which showed a significantly lower expression compared to the corresponding primary tumors (p = 0.02 and p = 0.03, respectively).
  
  
  CONCLUSIONS
  Targeting the GRPR and SSTR2 for nuclear imaging and/or treatment has the potential to improve BC care in primary as well as metastatic disease.
authors.affiliation: Department of Radiology & Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Simone U
authors.initials: SU
authors.lastname: Dalm
authors.affiliation: Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Willemijne A M E
authors.initials: WA
authors.lastname: Schrijver
authors.affiliation: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Anieta M
authors.initials: AM
authors.lastname: Sieuwerts
authors.affiliation: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Maxime P
authors.initials: MP
authors.lastname: Look
authors.affiliation: Department of Pathology, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Angelique C J
authors.initials: AC
authors.lastname: Ziel-van der Made
authors.affiliation: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Vanja
authors.initials: V
authors.lastname: de Weerd
authors.affiliation: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: John W
authors.initials: JW
authors.lastname: Martens
authors.affiliation: Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: van Diest
authors.affiliation: Department of Radiology & Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Marion
authors.initials: M
authors.lastname: de Jong
authors.affiliation: Department of Pathology, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Carolien H M
authors.initials: CH
authors.lastname: van Deurzen
mesh_terms: D001345:Autoradiography; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D011877:Radionuclide Imaging / Q000379:methods; D018004:Receptors, Bombesin / Q000187:drug effects* / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018004:Receptors, Bombesin; D017481:Receptors, Somatostatin; C574734:SSTR2 protein, human