VALIDATION OF NEUROTENSIN TETRA-BRANCHED PEPTIDES AS TUMOR TARGETING AGENTS IN PANCREAS, COLON AND BLADDER CARCINOMA

Abstract

The identification of new tumor targeting agents, which might allow either cancer cell tracing or ther- apy, is a crucial issue in cancer research. Membrane receptors for endogenous peptides such as neu- rotensin, somatostatin, bombesin and many others are over-expressed in different human cancers and could therefore be targeted as tumor-specific antigens. In the meantime the extremely short half-life of pep- tides impeded their development for effective pep- tide-based tumor targeting strategies. We synthesized tetra-branched neurotensin peptides (NT4), which ensure extremely long half-life main- taining peptide specificity and increasing avidity through multimeric binding. Moreover this bio-syn- thetical strategy allows a considerable modularity of peptides through the conjugation of different func- tional unit, such as fluorophore, radioactive moieties or chemotherapeutic drugs. Aim of our studies is to validate NT4 for cancer cell tracing in different human tumors. In this view we use fluorophore-conjugated NT4 to discriminate be- tween tumor and healthy tissue obtained by surgical samples from pancreas, colon and bladder carcinoma. Peptide binding on tumor and healthy biopsies was measured in each patient by quantitative analysis of confocal microscopy images. These results show a considerable difference in fluorescence emission be- tween healthy and tumor samples in colon, pancreas and bladder cancer, opening the way to the develop- ment of NT4 as selective diagnostic tools for these pathologies. Moreover our peptides can be conju- gated with different chemotherapeutic moieties in order to allow the selective killing of tumor cells.