Platelet Factor-4 Inhibits the Mitogenic Activity of VEGF
and VEGF
Using Several Concurrent Mechanisms (*)
- Stela Gengrinovitch(1),
- Sheryl M. Greenberg(2),
- Tzafra Cohen(1)(3),
- Hela Gitay-Goren(1),
- Patricia Rockwell(4),
- Theodore E. Maione(2),
- Ben-Zion Levi(3) and
- Gera Neufeld(1)(§)
- From the (1) Department of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel, the
- (2)Repligen Corporation, Cambridge, Massachusetts 02139, the
- (3)Department of Food Engineering and Biotechnology, Technion, Israel Institute of Technology, Haifa, 32000, Israel, and
- (4)ImClone Systems Inc., New York, New York 10014
- § To whom correspondence should be addressed. Tel.: 972-4294216; Fax: 972-4225153; E-mail: gera{at}techunix.technion.ac.il.
Abstract
The 121-amino acid form of vascular endothelial growth factor (VEGF
) and the 165-amino acid form (VEGF
) are mitogenic for vascular endothelial cells and induce angiogenesis in vivo. VEGF
possesses a heparin binding ability and in the absence of heparin-like molecules does not bind efficiently to the VEGF receptors
of vascular endothelial cells. The binding of 
I-VEGF
to the VEGF receptors of endothelial cells, and the heparin-dependent binding of 
I-VEGF
to a soluble extracellular domain of the VEGF receptor KDR/flk-1, were inhibited by the angiogenesis inhibitor platelet factor-4 (PF4). In contrast, PF4 was not able to inhibit the binding
of VEGF
, a VEGF isoform which lacks a heparin binding capacity, to the VEGF receptors of the cells or to KDR/flk-1. These results indicate that PF4 may inhibit VEGF
binding to VEGF receptors by disrupting the interaction of VEGF
with cell surface heparan sulfates. Since PF4 mutants lacking a heparin binding ability retain their anti-angiogenic activity,
alternative inhibitory mechanisms were also examined. 
I-PF4 bound with high affinity (K
5 
10
M) to VEGF
-coated wells. The binding of 
I-PF4 to the VEGF
-coated wells was inhibited by several types of heparin binding proteins, including unlabeled PF4 and unlabeled VEGF
. The binding was not inhibited by proteins which lack a heparin binding capacity, nor was it inhibited by VEGF
. Heparinase did not inhibit the binding of 
I-PF4 to VEGF
, indicating that heparin-like molecules are not required. These experiments suggest that PF4 can bind to heparin binding
proteins such as VEGF
leading to an inhibition of their receptor binding ability. In agreement with these results, we have observed that PF4 inhibits
efficiently the VEGF
induced proliferation of vascular endothelial cells. Unexpectedly, PF4 also inhibited efficiently the VEGF
-induced proliferation of the cells, indicating that PF4 can disrupt VEGF receptor mediated signal transduction using an unknown
mechanism which does not interfere with VEGF
binding.
Footnotes
-
↵* This work was supported by grants from the Israel Ministry of Science, joint programs with Germany (DKFZ and GSF), by a grant from the Israel Academy of Sciences and Humanities, and by a grant from the Israel Cancer Research Fund (ICRF) (to G. N.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- VEGF
-
vascular endothelial growth factor
- VEGF
-
165-amino acid form of vascular endothelial growth factor
- VEGF
-
121-amino acid form of vascular endothelial growth factor
- ABAE
-
bovine aortic arch-derived endothelial cells
- aFGF
-
acidic fibroblast growth factor
- bFGF
-
basic fibroblast growth factor
- HUE
-
human umbilical vein-derived endothelial cells
- PBS
-
Dulbecco's phosphate-buffered saline
- PF4
-
platelet factor 4.
-
↵2H. Gitay-Goren, T. Cohen, S. Tessler, S. Soker, S. Gengrinovitch, P. Rockwell, M. Klagsbrun, B.-Z. Levi, and G. Neufeld, unpublished data.
