Modulation of VEGF Bioavailability in Breast Tumors by Direct MMP Cleavage
Abstract
Vascular endothelial growth factor(VEGF) is one of the most relevant mediators of capillary recruitment and stimulator of tumor-angiogenesis. Substantial evidence implicates VEGF in the vascularization of tumors, including those related to the mammary gland. Once synthesized and secreted by the normal mammary gland, VEGF is frequently bound to extracellular matrix molecules, remaining inaccessible to its receptors present on endothelial cells. Subsequent release of VEGF from extracellular sources is thought to require break-down of matrix proteins by matrix metalloproteinases(MMPs). However, its exact regulation is unknown. We previously found that MMP-3 cleaves VEGF165(^22kDa) directly, releasing two major VEGF165 cleavage products, ^16kDa and ^6kDa. Here we report that, by western analysis with epitope-specific antibodies, Edman sequencing and MALDI/MS analysis for both fragments to determine the cleavage sites in VEGF, MMP-3 cleaves VEGF165, releasing the ^16kDa fragment that is functionally active as it phosphorylates VEGFR-2 in porcine aortic endothelial cells at a level comparable by conditioned media from uncleaved VEGF165-expressing cells. The data imply that VEGF may be processed extracellulary releasing bioactive fragments and that this proteolysis might offer an important mode for regulation on VEGF bioavailability.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2003
- Accession Number
- ADA417785
Entities
People
- Luisa Iruela-arispe
- Sunyoung Lee
Organizations
- University of California, Los Angeles