Synergistic Damage of Tumor Vessels with Ultra Low-Dose Endothelial-Monocyte Activating Polypeptide-II and Neovasculature-Targeted Tumor Necrosis Factor-α

Abstract

High-dose endothelial-monocyte activating polypeptide II (EMAP-II), a tumor-derived antiangiogenic cytokine, can sensitize tumor vasculature to the damaging activity of highdose tumor necrosis factor (TNF)-A. However, this combination cannot be used for systemic treatment of patients because of prohibitive toxicity. We have found that this limitation can be overcome by combining a TNF-targeting strategy with the use of ultra low-dose EMAP-II. Coadministration of 0.1 ng of EMAP-II and 0.1 ng of CNGRCG-TNF (NGR-TNF), a peptide-TNF conjugate able to target tumor blood vessels, inhibited lymphoma and melanoma growth in mice, with no evidence of toxicity. This drug combination induced endothelial cell apoptosis in vivo and, at later time points, caused reduction of vessel density and massive apoptosis of tumor cells. Liganddirected targeting of TNF was critical because the combination of nontargeted TNF with EMAP-II was inactive in these murine models. The synergism was progressively lost when the dose of EMAP-II was increased in the nanogram to microgram range, supporting the concept that the use of low-dose EMAP-II is critical. Studies on the mechanism of this paradoxical behavior showed that EMAP-II doses >1 ng induce the release of soluble TNF receptor 1 in circulation, a strong counter-regulatory inhibitor of TNF. Tumor vascular targeting with extremely low amounts of these cytokines may represent a new strategy for cancer treatment. [Cancer Res 2008;68(4): 1154-61]

The tumor vessel targeting agent NGR-TNF controls the different stages of the tumorigenic process in transgenic mice by distinct mechanisms

“…Notably, in this phase we detected a decrease of the vascular surface area most likely related to the high level of CD13 expression on endothelial cells and the cytotoxic activity of NGR-mTNF. 41 In support of the hypothesis of a direct effect of NGR-mTNF on endothelial cells, we observed …”

Tumor vasculature‐targeted delivery of tumor necrosis factor‐α*

“…Recently, RGD and other targeted motifs have been used for tumor-targeted delivery of recombinant TNF-a. [28][29][30][31] Among these, NGR-TNF, an aminopeptidase N (CD13) ligand that targets activated blood vessels in tumors, looks very promising. In this molecule, TNF-a is fused with the C terminus of CNGRCG peptide.…”

“…It has demonstrated very little systemic toxicity as well as efficient antitumor activity in several animal models. 29,30 However, published reports on the tumor-targeted delivery of TNF-a have used only recombinant protein. The delivery of recombinant protein has its own limitations.…”

Development of Cyclic NGR Peptides with Thioether Linkage: Structure and Dynamics Determining Deamidation and Bioactivity

“…7 Cyclic and/or linear peptides containing either the c [CNGRC] or the GNGRG motives were described as appropriate target ligands in delivery of tumor necrosis factor alpha (TNF-α), 5,21,22 interferon gamma (IFNγ), [23][24][25] liposomal doxorubicin 26,27 and Pt-complex 28,29 as well as radio metal isotope labeled derivatives for PET and SPECT. 30,31 By comparing c [CNGRC] and GNGRG, a cyclic and a linear peptide, not only the higher CD13 binding affinity of cyclic variant was detected but also its increased stability in PBS solution (half-lives were [6][7][8] h and 3-4 h, respectively at pH 7.3, 37°C) and in serum (5 h and 3 h, respectively) was measured.…”