NT4 AS PROMISING CANCER-SELECTIVE THERANOSTIC PEPTIDE

NT4 is a tetrabranched peptide containing four neurotensin sequences that selectively binds human cancer cells and tissues. The high selectivity of NT4 toward cancer resides in the high-affinity binding to HSPGs (heparan sulfate proteoglycans) that are over-expressed on tumor cell membrane. Here we demonstrate that NT4 interferes with HSPG-modulated activities such as tumor cell adhesion, migration and matrix invasion. Our tetrabranched peptide was used as a specific tool to analyze the role of sulfated glycosaminoglycans in signaling events regulating the directional migration of cancer cells. NT4 abolishes oriented migration, inducing disorganization of actin filaments and stress fibers, and increasing the number of filopodia. This happens without any change in activation of β1 integrins or focal adhesion kinase, but with a decrease in Rac1 activity. Data obtained suggest that HSPGs might work as primary conductors of directional cell migration by regulating Rac1 activity through an integrin-independent signaling pathway. Furthermore, peptide ability to discriminate between tumor and healthy tissues in different human cancer specimens can be exploited by conjugating NT4 with different functional units, such as tracking molecule or chemotherapeutical drug for cancer cell imaging and therapy, respectively. In this work, NT4 capability to efficiently deliver drugs for cancer therapy is demonstrated. Methotrexate-conjugated NT4 (NT4-MTX) allows drug resistance to be bypassed in methotrexate-resistant human breast cancer cells lacking expression of folate reduced carrier; an increased activity of the chemotherapeutic agent is due to NT4-mediated drug internalization inside the cells. We also focus on construction, validation, in vitro and in vivo analysis of novel theranostic nanodevices, functionalizing near-infrared quantum dots with our tetrabranched peptide (NT4-QDs). We observed specific uptake of the device in human cancer cells in in vitro experiments; animal models of cancer were also set up to test nano-imaging with NT4-QDs obtaining very promising results. The tumor selectivity and its role as carrier of tracers, drugs or nanoparticles demonstrate the promising features of NT4 to be exploited as cancer theranostic, which may reduce tumor aggressiveness and also metastatic potential, in personalized oncological application.