Targeting endothelial cells overexpressing VEGFR-2: selective toxicity of Shiga-like toxin-VEGF fusion proteins

Bioconjug Chem. Nov-Dec 2001;12(6):1066-73. doi: 10.1021/bc015534j.

Abstract

Growing endothelial cells at the sites of angiogenesis express high numbers of VEGF receptors and therefore may be particularly sensitive to VEGF-mediated drug delivery. To test this hypothesis we have constructed a protein containing the catalytic A-subunit of Shiga-like toxin I fused to VEGF121 (SLT-VEGF/L). Wild-type A-subunit is a site-specific N-glycosidase of 28S rRNA that inhibits protein synthesis after being delivered into cells by separate cell-binding B-subunits. SLT-VEGF/L retains functional activities of both SLT and VEGF121 moieties, since it inhibits protein synthesis in a cell-free translation system and induces VEGFR-2 tyrosine autophosphorylation. SLT-VEGF/L selectively inhibits growth of porcine endothelial cells expressing 2.5 x 10(5) VEGFR-2/cell with an IC50 of 0.2 nM and rapidly induces apoptosis at concentrations >1 nM. We found that sensitivity of VEGFR-2 transfected PAE cells to SLT-VEGF/L declined as the cellular VEGFR-2 density decreased; PAE cells expressing 25000 VEGFR-2/cell were as sensitive as parental cells lacking the receptor. Growth inhibition and induction of apoptosis by SLT-VEGF/L require intrinsic N-glycosidase activity of the SLT moiety, but take place without significant inhibition of protein synthesis. Selective cytotoxicity of SLT-VEGF/L against growing endothelial cells overexpressing VEGFR-2 suggests that it may be useful in targeting similar cells at the sites of angiogenesis.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Angiogenesis Inhibitors / pharmacokinetics
  • Angiogenesis Inhibitors / toxicity
  • Animals
  • Apoptosis / drug effects
  • Cell Division / drug effects
  • Cells, Cultured
  • Drug Delivery Systems*
  • Endothelial Growth Factors / metabolism
  • Endothelium, Vascular / drug effects*
  • Endothelium, Vascular / metabolism
  • Lymphokines / metabolism
  • Protein Binding
  • Protein Synthesis Inhibitors / pharmacology
  • Receptor Protein-Tyrosine Kinases / biosynthesis
  • Receptor Protein-Tyrosine Kinases / metabolism*
  • Receptors, Growth Factor / biosynthesis
  • Receptors, Growth Factor / metabolism*
  • Receptors, Vascular Endothelial Growth Factor
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / toxicity*
  • Shiga Toxin 1 / toxicity
  • Swine
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors

Substances

  • Angiogenesis Inhibitors
  • Endothelial Growth Factors
  • Lymphokines
  • Protein Synthesis Inhibitors
  • Receptors, Growth Factor
  • Recombinant Fusion Proteins
  • Shiga Toxin 1
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • Receptor Protein-Tyrosine Kinases
  • Receptors, Vascular Endothelial Growth Factor