In vitro and in vivo studies of a VEGF121/rGelonin chimeric fusion toxin targeting the neovasculature of solid tumors

Liesbeth M. Veenendaal, Hangqing Jin, Sophia Ran, Lawrence Cheung, Nora Navone, John W. Marks, Johannes Waltenberger, Philip Thorpe, Michael G. Rosenblum

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129 Scopus citations

Abstract

Vascular endothelial growth factor (VEGF) plays a key role in the growth and metastasis of solid tumors. We generated a fusion protein containing VEGF121 linked by a flexible G4S tether to the toxin gelonin (rGel) and expressed this as a soluble protein in bacteria. Purified VEGF121/rGel migrated as an 84-kDa homodimer under nonreducing conditions. VEGF121/rGel bound to purified, immobilized Flk-1, and the binding was competed by VEGF121. Both VEGF121/rGel and VEGF121 stimulated cellular kinase insert domain receptor (KDR) phosphorylation. The VEGF121/rGel fusion construct was highly cytotoxic to endothelial cells overexpressing the KDR/Flk-1 receptor. The IC50 of the construct on dividing endothelial cells expressing 105 or more KDR/Flk-1 receptors per cell was 0.5-1 nM, as compared with 300 nM for rGel itself. Dividing endothelial cells overexpressing KDR were approximately 60-fold more sensitive to VEGF121/rGel than were nondividing cells. Endothelial cells overexpressing FLT-1 were not sensitive to the fusion protein. Human melanoma (A-375) or human prostate (PC-3) xenografts treated with the fusion construct demonstrated a reduction in tumor volume to 16% of untreated controls. The fusion construct localized selectively to PC-3 tumor vessels and caused thrombotic damage to tumor vessels with extravasation of red blood cells into the tumor bed. These studies demonstrate the successful use of VEGF121/rGel fusion construct for the targeted destruction of tumor vasculature in vivo.

Original languageEnglish (US)
Pages (from-to)7866-7871
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue number12
DOIs
StatePublished - Jun 11 2002

ASJC Scopus subject areas

  • General

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