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Signaling through Raf-1 in the neovasculature and target validation by nanoparticles
1Center for Extracellular Matrix Biology, Institute of Biosciences and Technology, Texas A&M University System-Health Science Center, 2121 W. Holcombe Blvd, Houston, TX-77030, USA. kwary@ibt.tamushsc.edu
Abstract:
A recent study demonstrated that vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) activate Raf-1 kinase in an experimental neovasculature system. The study showed that bFGF and VEGF activate p21-activated protein kinase-1 (PAK-1) and Src kinase, respectively. PAK-1 and Src kinases phosphorylate specific serine and tyrosine residues within the activation loop of Raf-1 kinase. Their findings further suggest that phosphorylation at these sites protects endothelial cells from apoptosis induced by both intrinsic and extrinsic factors. The tumor neovasculature provides specific molecular markers or "zip codes". This group of investigators has previously shown that nanosphere-aided targeting of the neovasculature with mutant Raf-1 causes regression of the tumor vasculature. Thus, nanoparticles coated with "zip code"-specific homing biomolecules may be useful for delivering anti-angiogenic molecules that can induce tumor regression.
Insights
Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) activate Raf-1 kinase, protecting endothelial cells from apoptosis. This finding supports nanoparticle delivery of anti-angiogenic molecules for tumor regression.
Area of Science:
- Molecular biology
- Cell biology
- Cancer research
Background:
- Tumor neovasculature presents unique molecular markers.
- Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) play roles in angiogenesis.
- Raf-1 kinase is a key signaling molecule in cellular pathways.
Purpose of the Study:
- To investigate the activation pathways of Raf-1 kinase by VEGF and bFGF.
- To determine the role of Raf-1 kinase phosphorylation in endothelial cell survival.
- To explore the potential of targeting tumor neovasculature for cancer therapy.
Main Methods:
- Experimental neovasculature system used to study kinase activation.
- Analysis of p21-activated protein kinase-1 (PAK-1) and Src kinase activation.
- Phosphorylation site identification on Raf-1 kinase.
Main Results:
- VEGF activates Src kinase, while bFGF activates PAK-1.
- PAK-1 and Src kinases phosphorylate specific sites on Raf-1 kinase.
- Phosphorylation of Raf-1 protects endothelial cells from apoptosis.
Conclusions:
- VEGF and bFGF signaling pathways converge on Raf-1 kinase activation.
- Targeting tumor-specific neovasculature with nanoparticles offers a therapeutic strategy.
- Nanoparticle-mediated delivery of anti-angiogenic agents can induce tumor regression.