Targeting of endothelial KDR receptors with 3G2 immunoliposomes in vitro.
Immunoliposomes (IL) containing anti-angiogenic drugs directed selectively to the easily accessible kinase insert domain containing receptor (KDR) vascular endothelial growth factor (VEGF), which is predominantly expressed on tumour vessels are a promising tool to inhibit tumour angiogenesis. To explore this strategy, we have prepared fluorescent-labelled IL presenting antibodies against the KDR receptor (3G2) on their surface. 3G2-IL were composed of egg phosphatidylcholine and cholesterol (6:4), containing 2 mol% of the new thiol reactive linker lipid O-(3-cholesteryloxycarbonyl)propionyl-O'-m-maleimido-benzoyl tetraethylene glycol. Specific binding of 3G2-IL to immobilised recombinant KDR was used to show the maintenance of sufficient immunoreactivity of 3G2 antibodies upon the coupling procedure. 3G2-IL bound to Chinese hamster ovarian (CHO) cells stably transfected to overexpress KDR to a five times higher amount as compared to mock-transfected CHO cells. Subsequently, specific binding of 3G2-IL to KDR could also be demonstrated on KDR expressing cells, human umbilical vein endothelial cells and human microvascular endothelial cells, whereas only low binding of 3G2-IL to NIH-3T3 mouse fibroblast cells, which do not express KDR, was found. The binding of 3G2-IL to KDR receptors could not be blocked by VEGF, suggesting that the binding site for VEGF is not identical with the epitope recognised by 3G2. We could demonstrate that 3G2-IL is able to bind in vitro even in the presence of high levels of VEGF.
Benzinger
P
P
Tumor Biology Center, Division of Medical Research, Department of Medical Oncology, Breisacher Strasse 117, D-79106, Freiburg, Germany.
Martiny-Baron
G
G
Reusch
P
P
Siemeister
G
G
Kley
J T
JT
Marmé
D
D
Unger
C
C
Massing
U
U
D016475:3T3 Cells; D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D016228:Endothelial Growth Factors / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D005452:Fluoresceins; D006801:Humans; D008081:Liposomes; D008222:Lymphokines / Q000378:metabolism; D051379:Mice; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D040262:Receptors, Vascular Endothelial Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D005452:Fluoresceins; D008081:Liposomes; D008222:Lymphokines; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; C007740:fluorexon