Synthesis and biological activity of stable branched neurotensin peptides for tumor targeting

Abstract

Receptors for endogenous regulatory peptides, like the neuropeptide neurotensin, are overexpressed in several human cancers and can be targets for peptide-mediated tumor-selective therapy. Peptides, however, have the main drawback of an extremely short half-life in vivo. We showed that neurotensin and other endogenous peptides, when synthesized as dendrimers, retain biological activity and become resistant to proteolysis. Here, we synthesized the neurotensin functional fragment NT(8-13) in a tetrabranched form linked to different units for tumor therapy or diagnosis. Fluorescent molecules were used to monitor receptor binding and internalization in HT29 human adenocarcinoma cells and receptor binding in HT29 tumor xenografts in nude mice. Linking of chemotherapic molecules like chlorin e6 and methotrexate to dendrimers resulted in a dramatic increase in drug selectivity, uptake of which by target cells became dependent on peptide receptor binding. When nude mice carrying human tumor xenografts were treated with branched NT(8-13)-methotrexate, a 60% reduction in tumor growth was observed with respect to mice treated with the free drug. [Mol Cancer Ther 2007;6(9):2441 -8]

Liposomes derivatized with multimeric copies of KCCYSL peptide as targeting agents for HER-2-overexpressing tumor cells

“…Several papers have reported the capacity of peptides synthesized in their branched form to enhance resistance toward proteases and to increase linear peptide biological activity through multivalent binding. [16][17][18] Recently, some evidence that these properties are also maintained when the peptide is bounded on the external liposomal surface have been demonstrated. 19,20 Liposomes were chosen as the vector since they can accommodate large quantities of relevant therapeutic drugs in their lumen.…”

Branched peptides as novel tumor-targeting agents for bladder cancer

“…A proof of concept has been obtained with peptides reproducing the sequence of the endogenous peptide neurotensin (NT) in its tetrameric form (NT4), whose receptors are overexpressed in several human malignancies. NT4 binds to cell membrane receptors more efficiently than the monomeric homologous sequence, and can be coupled to different effector units for either imaging or therapy of cancer cells [14]. Indeed, NT4 can efficiently discriminate between tumor and healthy tissue in human surgical samples from colon or pancreas adenocarcinoma, as recently reported in a large series of patients [15].…”

“…The liposome-NT4 strategy allows the possibility of internalizing a greater load of therapeutic and diagnostic (theranostic) agents inside the cell membrane, and potentially overcoming cell resistance due to the lack of receptors on anaplastic cell clones [17]. Indeed, the switch to a receptor-selective drug internalization may have three very important consequences: it can dramatically reduce drug nonspecific cytoxicity; it increases in vivo activity of the drug; and it may induce reversal of innate cell resistances, when these are produced by a mechanism of cell internalization or export of drugs [14]. Branched peptides may increase the selectivity of small molecules towards tumor cells, thus acting as 'Trojan horses' that selectively transport chemotherapy drugs into tumor cells, since they have the ability of turning nonspecific cytotoxic drugs into tumor-selective agents, which presently have a limited use in oncology due to their low selectivity and high nonspecific toxicity [14].…”

“…Indeed, the switch to a receptor-selective drug internalization may have three very important consequences: it can dramatically reduce drug nonspecific cytoxicity; it increases in vivo activity of the drug; and it may induce reversal of innate cell resistances, when these are produced by a mechanism of cell internalization or export of drugs [14]. Branched peptides may increase the selectivity of small molecules towards tumor cells, thus acting as 'Trojan horses' that selectively transport chemotherapy drugs into tumor cells, since they have the ability of turning nonspecific cytotoxic drugs into tumor-selective agents, which presently have a limited use in oncology due to their low selectivity and high nonspecific toxicity [14]. On these bases, NT4 as a theranostic agent has a high potentiality and represents a very interesting field of investigation.…”

Receptor binding peptides for target-selective delivery of nanoparticles encapsulated drugs

“…109 NT shows a very short half-life in vivo; Falciani et al designed tetrabranched peptides (NT4) containing four copies of the active NT sequence and acting as tumor targeting agents. 110 It is well known that peptides synthesized in a branched arrangement not only become resistant to proteases but also increase linear peptide biological activity through multivalent binding. Additionally, branched NT peptides have been proven to discriminate between binding of tumor versus healthy tissue in human surgical samples, validating increasing interest.…”