Antiangiogenic and Antitumoral Effects Mediated by a Vascular Endothelial Growth Factor Receptor 1 (VEGFR-1)-Targeted DNAzyme

Liangfang Shen,Yan Chen,Lifang Yang,Ying Wang,Qin Zhou,Lun-Quan Sun,Zhijie Xu,Weihua Liao

doi:10.2119/molmed.2013.00090

Abstract

Antiangiogenesis is a promising antitumor strategy that inhibits tumor vascular formation to suppress tumor growth. DNAzymes are synthetic single-strand deoxyribonucleic acid (DNA) molecules that can cleave ribonucleic acids (RNAs). Here, we conducted a comprehensive in vitro selection of active DNAzymes for their activity to cleave the vascular endothelial growth factor receptor (VEGFR-1) mRNA and screened for their biological activity in a matrigel tube-formation assay. Among the selected DNAzymes, DT18 was defined as a lead molecule that was further investigated in several model systems. In a rat corneal vascularization model, DT18 demonstrated significant and specific antiangiogenic activity, as evidenced by the reduced area and vessel number in VEGF-induced corneal angiogenesis. In a mouse melanoma model, DT18 was shown to inhibit B16 tumor growth, whereas it did not affect B16 cell proliferation. We further assessed the DT18 effect in mice with established human nasopharyngeal carcinoma (NPC). A significant inhibition of tumor growth was observed, which accompanied downregulation of VEGFR-1 expression in NPC tumor tissues. To evaluate DT18 effect on vasculature, we performed dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) on the human NPC xenograft mice treated with DT18 and showed a reduction of the parameter of K(trans) (volume constant for transfer of contrast agent), which reflects the condition of tumor microvascular permeability. When examining the safety and tolerability of DT18, intravenous administration of Dz18 to healthy mice caused no substantial toxicities, as shown by parameters such as body weight, liver/kidney function, and histological and biochemical analyses. Taken together, our data suggest that the anti-VEGFR-1 DNAzyme may be used as a therapeutic agent for the treatment of cancer, such as NPC.

Highlights

Angiogenesis is a physiological process required for embryonic development, the menstrual cycle and wound healing [1,2]
For anti–VEGFR-1 DNAzymes to be screened in human cells and tested in mouse models, it is necessary to make DNAzymes that would target both human and murine/rat sequences
The suggested mechanism of the Avastin resistance is that vascular endothelial growth factor (VEGF) receptors have multiple ligands and neutralizing VEGFA by Avastin may result in the resistance caused by alternative ligands [14]

Summary

Introduction

Angiogenesis is a physiological process required for embryonic development, the menstrual cycle and wound healing [1,2]. The angiogenic process involves interaction between angiogenic factors and endothelial cells (ECs) and can be manipulated directly or indirectly. In contrast to conventional cytotoxic agents, antiangiogenic agents work by blocking oxygen and nutrient supplies to tumors, thereby suppressing their growth. An antiangiogenic agent is less likely than a cytotoxic agent to induce drug resistance because it targets genetically stable ECs instead of genetically unstable tumor cells [5]. An antiangiogenic approach would have fewer off-target side effects because only tumor-associated ECs proliferate and express specific markers, such as integrin αvβ, E-selectin and vascular endothelial growth factor (VEGF) receptors, unlike quiescent normal ECs [5].

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Conclusion