In vivo and in vitro characterization of CCK8 bearing a histidine-based chelator labeled with 99mTc-tricarbonyl

Luca D. D'Andrea, Irma Testa, Maria Rosaria Panico, Rossella Di Stasi, Corradina Caracò, Laura Tarallo, Claudio Arra, Antonio Barbieri, Alessandra Romanelli, Luigi Aloj

Research output: Contribution to journalArticlepeer-review


The development of receptor targeting radiolabeled ligands has gained much interest in recent years for diagnostic and therapeutic applications in nuclear medicine. Cholecystokinin (CCK) receptors have been shown to be overexpressed in a subset of neuroendocrine and other tumors. We are evaluating binding and biodistribution properties of a CCK8 peptide derivative labeled with 99mTc(I)-tricarbonyl. The CCK8 peptide was modified at its N-terminus by adding to its N-terminus two lysine-histidine modules (KH), where histidine is coupled to the side chain of the lysine ((KH)2-CCK8). 99mTc(I)-tricarbonyl was generated with the IsoLinkTM kit. A431 cells stably transfected with a cDNA encoding for the human CCK2 receptor were utilized to determine binding affinity, internalization, and retention of the labeled peptide, in comparison with wild-type A431 cells. A nude mouse tumor model was obtained by generating A431-CCK2R and A431-control tumors in opposite flanks of the animals. High specific activity labeling with 99mTc was achieved. In A431-CCK2R cells, specific saturable binding was observed as well as evident internalization of the radiolabeled peptide after binding. Biodistribution experiments showed rapid, specific localization of (KH)2-CCK8 on A431-CCK2R xenografts compared with control tumors, although absolute uptake values were not markedly higher compared with background activity. Clearance of unbound radioactivity was both urinary and hepatobiliary. In imaging experiments, while targeting to CCK2R positive tumors could be appreciated, there was poor contrast between target and nontarget areas. (KH)2-CCK8 shows adequate in vitro and in vivo properties for CCK2R targeting although improvement of biodistribution warrant further development.

Original languageEnglish
Pages (from-to)707-712
Number of pages6
Issue number5
Publication statusPublished - 2008


  • Carbonyl
  • Cholecystokinin receptors
  • Imaging
  • Organometallic complexes
  • Radiopeptide
  • Technetium

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Biomaterials
  • Organic Chemistry


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