title: Improved radiopharmaceutical based on 99mTc-Bombesin-folate for breast tumour imaging.
abstract: BACKGROUND
  Clinical studies in women using technetium-99m (Tc)-Bombesin have shown successful radionuclide imaging of breast tumours overexpressing gastrin-releasing peptide receptors (GRPRs). Recent studies have demonstrated that most breast tumours overexpress folate receptors (FRα).
  
  
  OBJECTIVE
  The aim of this work was to synthesize the Lys(α,γ-Folate)-Lys(Tc-EDDA/HYNIC)-Bombesin (1-14) conjugate (Tc-Bombesin-Folate), as well as to assess the in-vitro and in-vivo potential of the radiopharmaceutical to target FRα and GRPR.
  
  
  METHODS
  LysLys(HYNIC)-Bombesin (1-14) was conjugated to folic acid and the product was purified by size-exclusion high-performance liquid chromatography. Ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used for chemical characterization. Tc labelling was performed using ethylenediamine-N,N'-diacetic acid/tricine as coligands. In-vitro binding studies were carried out in T47D breast cancer cells (positive for FRα and GRPR). Biodistribution studies and micro-single-photon emission computed tomography/computed tomography imaging were carried out on athymic mice with T47D-induced tumours.
  
  
  RESULTS
  High-performance liquid chromatography analyses indicated that the radioconjugate was obtained with high radiochemical purity (96±2.1%). In-vitro and in-vivo results showed significant uptake of the radiopharmaceutical in T47D cells and tumours (5.43% ID/g), which was significantly inhibited by preincubation with cold folic acid or cold Bombesin.
  
  
  CONCLUSIONS
  The Tc-Bombesin-folate heterobivalent radiopharmaceutical significantly enhances in-vivo tumour uptake because of the concomitant interaction with FRα and GRPR.
authors.affiliation: aInstituto Nacional de Investigaciones Nucleares, Ocoyoacac bUniversidad Autónoma del Estado de México, Toluca cInstituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Tlalpan, Mexico City, Mexico.
authors.forename: Liliana
authors.initials: L
authors.lastname: Aranda-Lara
authors.forename: Guillermina
authors.initials: G
authors.lastname: Ferro-Flores
authors.forename: Flor de María
authors.initials: Fde M
authors.lastname: Ramírez
authors.forename: Blanca
authors.initials: B
authors.lastname: Ocampo-García
authors.forename: Clara
authors.initials: C
authors.lastname: Santos-Cuevas
authors.forename: Lorenza
authors.initials: L
authors.lastname: Díaz-Nieto
authors.forename: Keila
authors.initials: K
authors.lastname: Isaac-Olivé
mesh_terms: D000818:Animals; D001839:Bombesin / Q000737:chemistry*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D005260:Female; D058975:Folate Receptor 1 / Q000378:metabolism; D005492:Folic Acid / Q000737:chemistry*; D006801:Humans; D051379:Mice; D015609:Organotechnetium Compounds / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics; D011854:Radiochemistry; D019275:Radiopharmaceuticals / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics; D018004:Receptors, Bombesin / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D058975:Folate Receptor 1; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D018004:Receptors, Bombesin; C031123:technetium Tc 99m ethylenediamine-N,N-diacetic acid; D005492:Folic Acid; D004492:Edetic Acid; D001839:Bombesin