Induction of tumor necrosis factor-α in solid tumor region by the orally administered synthetic muramyl dipeptide analogue, romurtide

Inhibitory Effects of Multivalent Polypeptides on the Proliferation and Metastasis of Breast Cancer Cells

The susceptibility of peptide drugs to enzymatic degradation has limited their clinical applications. To overcome this limitation, we attached the peptide tyroserleutide (YSL) to a molecular scaffold in order to produce homogeneous monovalent, bivalent, tetravalent, and octavalent YSL dendrimers with highly ordered secondary structures. These multivalent YSL dendrimers were resistant to proteolysis and were better able to induce cytotoxicity in tumor cells in vitro as compared with monomeric peptides. These multivalent YSL dendrimers were also better able to constrain tumor cell metastasis. Compared with monovalent YSL, the multivalent YSL dendrimers displayed enhanced in vivo antitumor activity and suppressed tumor growth and metastasis in BALB/c mice bearing 4T1 tumors. These findings indicate that multivalence can significantly enhance ligand potency and represent a potential method for the development of peptide drugs with high therapeutic potential.

Targeting tumors with peptides from natural sources

Peptide-based therapies offer the potential for non-genotoxic, genotype-specific alternatives, or adjuvants, to the current range of traditional cancer treatments. Such a patient-tailored cancer-cell-directed therapeutic approach should have fewer side effects and could well be more effective than the current drug- or combination-based regimens. Here, we review the potential of novel natural anticancer peptides such as necrotic peptides, apoptotic peptides, function-blocking peptides, antiangiogenic peptides and immunostimulatory peptides in the context of their ability to induce tumor regression. We focus on the therapeutic prospects of anticancer peptides and their possible application in tumor therapy.

Cancer relapse under chemotherapy: why TLR2/4 receptor agonists can help

Liver or lung metastases usually relapse under chemotherapy. Such life-threatening condition urgently needs new, systemic anticancer compounds, with original and efficient mechanisms of action. In B16 melanoma mice treated with cyclophosphamide, D'Agostini et al. [D'Agostini, C., Pica, F., Febbraro, G., Grelli, S., Chiavaroli, C., Garaci, E., 2005. Antitumour effect of OM-174 and Cyclophosphamide on murine B16 melanoma in different experimental conditions. Int. Immunopharmacol. 5, 1205-1212.] recently found that OM-174, a chemically defined Toll-like receptor(TLR)2/4 agonist, reduces tumor progression and prolongs survival. Here we review 149 articles concerning molecular mechanisms of TLR2/4 agonists, alone or in combination with chemotherapy. It appears that TLR2/4 agonists induce a well controlled tumor necrosis factor-alpha (TNF-alpha) secretion, at plasma levels known to permeabilize neoangiogenic tumor vessels to the passage of cytotoxic drugs. Moreover, TLR2/4 agonists induce inducible nitric oxide synthase (iNOS) expression, and nitric oxide is able to induce apoptosis of chemotherapy-resistant tumor cell clones. Finally, TLR2/4-stimulation activates dendritic cell traffic and its associated tumor-specific, cytotoxic T-cell responses. Therefore, parenteral TLR2/4 agonists seem promising molecules to prolong survival in cancer patients who relapse under chemotherapy.