A NEW AND SELECTIVE RADIOLABELED ALPHAVBETA3 PEPTIDE ANTAGONIST AS TRACER IN TUMOR DIAGNOSIS.

Angiogenesis, the process whereby new capillaries are formed by outgrowth from existing microvessels, is required for tumor growth and metastasis. The transmembrane cell-surface receptor ?V?3 has recently received increasingly attention, because of the critical role in tumor associated angiogenesis and metastasis formation . The restricted expression of integrin ?V?3 during tumor growth, invasion, and metastasis presents an interesting target for both detection and treatment of solid tumors. Targeting ?V?3 with radiolabelled ligands may provide information about the receptor status and enable the planning and the monitoring of therapeutic approaches. Recently we developed a novel ?V?3 antagonist that showed a high selectivity for the receptor. Adhesion assays, competitive binding assays and cross-linking experiments performed in human erythroleukemia K562 cells, stably cotransfected with cDNA of ?v or ?IIb and ?3, demonstrated the high selectivity for ?V?3 integrin. Starting from these evidences, RGDechi was covalently bound to the chelating agent DTPA able to give stable complexes of radionuclides, such as 111In and 90Y . The final goal has been to obtain a radiolabelled compound to be used in nuclear medicine as a diagnostic and therapeutic agent. In particular DTPA-RGDechi has been labeled with 111In and used in SPECT for diagnostic purpose. Moreover, the ligand RGDechi has been labeled with 18F for micro-PET in order to evaluate the use of this peptide for in vivo imaging.