Radiometal targeted tumor diagnosis and therapy with peptide hormones

Radiometal labeled peptide hormones are promising tools for a new generation of radiopharmaceuticals, because their receptors frequently are overexpressed in many human tumors. Furthermore, peptide hormones are characterized by different advantages for clinical application, such as high tumor-to-background ratios as well as rapid blood clearance. Peptidic tumor targeting agents can be sub-divided into the following segments: peptide, spacer, bifunctional chelator and radioisotope. Here the biological and chemical properties of peptide hormones are summarized as well as their prerequisites for their use as tumor targeting agents. Additionally, promising bifunctional chelators and radioisotopes for radiometal labeling are reviewed. Some few special peptide hormones that have been pre-clinically or clinically investigated are furthermore presented, such as somatostatin, bombesin (BBS) / gastrin releasing peptide (GRP), vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY). In vitro and in vivo investigations of the binding affinity, selectivity, metabolic stability, bioavailability and biodistribution of radiolabeled peptide hormones could lead to potential peptide-based tumor targeting agents for tumor diagnosis and therapy.