Expression of Genetically Engineered Therapeutic Fusion Protein Vascular Endothelial Growth Factor/ Shiga-Like Toxin (VEGF/SLT) in Escherichia coli for Targeting Angiogenesis

Abstract

Angiogenesis is a controlled process of growing new blood vessels under normal circumstances. However, in a large number of pathologies, such as solid tumor growth, angiogenesis is a crucial component of the disease process. Therefore, angiogenesis inhibitors are being investigated as potential therapeutics for tumor growth. During angiogenesis endothelial cells of existing blood vessels undergo a complex process of reshaping, migration, growth and organizing into new vessels. Vascular Endothelial Growth Factor (VEGF) is a central mediator for this process and acts via receptors whose expression is restricted almost exclusively to endothelial cells. Because of its selectivity, VEGF represents a unique vehicle for delivery inhibitors of angiogenesis to endothelial cells. Among potential inhibitors of angiogenesis is Shiga-like toxin-1 (SLT-I) produced by Escherichia coli O157:H7 and has the advantage that endothelial cells appear to be particularly sensitive to its action. The hypothesis of combining a SLT-I toxin with VEGF (VEGF/SLT) as a delivery vehicle would serve as a highly selective and active inhibitor of angiogenesis. To this end, fusion proteins containing VEGF₁₂₁ and two forms of Shiga-like toxin-I (A, or A₁) were developed and tested In vitro for activities to have the potential to inhibit angiogenesis in vivo. VEGF₁₂₁/A₁ fusion protein displayed the ability to induce auto-phosphorylation of the VEGF receptor KDR/flk-1 and displayed strong selective growth inhibition of cultured cells expressing KDR/flk-1 receptors. These results indicated that VEGF/A₁ fusion proteins is promising therapeutic agents that can be developed into powerful and selective inhibitors of angiogenesis.