Radiolabeled peptides: current and new perspectives.

Radiolabeled peptides have been the subject of research for over 20 years and during that time possibility/variety of peptide receptor imaging and later targeted radiotherapy increased significantly. The targeted receptors belong to the large family of G-protein-coupled receptors or tyrosine kinases receptors partially connected with them. They both regulate large signaling networks, control multiple cell functions and are implicated in many diseases including cancers. The essential feature of peptides used in nuclear medicine involves their ability to binding with high affinity and specify to their receptors overexpressed on tumor cells. Currently most important peptide radiotracers are somatostatin, GLP-1, bombesin, gastrin/cholecystokinin-2, neurokinin type 1, CXCR4, EGF, VEGF and integrins. These tracers are mainly based on nuclides which are radiometals or on 18F and may be used in both SPECT or PET techniques as well as for hybrid imaging. Using of chelators suitable for peptide labeling with diagnostic and therapeutic radionuclids enables the theranostic approach. In this review we will provide a brief overview over currently available radiopharmaceuticals based on different groups of peptides.