oa EDITORIAL [Hot Topic: Peptide-Receptor Ligands in Imaging and Therapy of Cancer (Guest Editor: Dr. Paolo Ruzza)]

Cancer is a challenging disease, characterized by a multitude of pathologically upregulated physiological processes that allow differentiating a tumor from normal tissue, providing a vast array of molecular targets. Successful cancer therapy hinges on early diagnosis and accurate staging. To this purpose, several strategies have been developed over the past two decades based on the use of small molecules or macromolecules (e.g., monoclonal antibodies and antibody fragments). Although some success has been achieved, the use of these molecules has been largely unsuccessful, mainly because of low specificity (small molecules) or limited target permeability (antibodies). A hope in the diagnosis and treatment of cancer is now represented by the development of peptide targeting molecules which have the advantage of being flexible messengers with high affinity and specificity for the target [1]. Indeed, since the work of Krenning et al. in 1989 [2] on the use of radiolabeled somatostatin analogues, the overexpression of different peptide-receptors in many human tumors makes them an attractive target for the design and synthesis of specific targeting molecules for both diagnosis and therapy of cancer, mainly after the labeling with radionuclides. The use of solid-phase peptide synthesis as well as of phage display technologies and combinatorial peptide chemistry has profoundly impacted the pool of available peptides for the development of efficient and specific targeting molecules, which can be coupled with the appropriate moieties (imaging probes or drugs) on demand with the help of sophisticated bioconjugation or radiolabeling techniques....