Angiogenesis
Angiogenesis is defined as the formation of new capillaries from preexisting blood vessels, and can be physiologic (e.g., during embryonic development, wound healing , and the menstrual cycle), or pathologic (as it happens in proliferative diabetic retinopathy, inflammatory arthritis, and when a tumor grows, invades, or metastasizes).
Angiostatin and K5 are potent inhibitors of angiogenesis. They are both proteolytic fragments of the human plasminogen; angiostatin consists of kringles 1-3 and K5 consists of kringle 5 of the NH2-terminal heavy chain of plasminogen.
Angiostatin binds to ATP-synthase on the endothelial cell surface (Moser et al. 1999), as well as to alphav beta3 (Tarui et al. 2001), and angiomotin (Troyanovsky et al. 2001). The voltage-dependent anion channel (VDAC) on the endothelial cell surface acts as a receptor for K5 (Gonzalez-Gronow et al. 2003).
We have demonstrated that angiostatin and K5 affixed to a solid phase were able to promote adhesion of 35S-metabolically labeled human microvascular endothelial cells (HMVEC). These data suggest that angiostatin and K5 may suppress neovascularization through interaction with adhesion complexes of the plasma membrane and the associated signal transduction pathways. Therefore, we examined the effects of angiostatin and K5 to the focal adhesion kinase (FAK), probing with phosphospecific antibodies in Western blots of cell lysate. K5 treatment increased the autophosphorylation of focal adhesion kinase (FAK) at Tyr397 in HMVEC adhered on tissue culture plastic, whereas angiostatin induced autophosphorylation of FAK in HMVEC attached to a fibronectin coated surface or tissue culture plastic. Hypoxic and acidic conditions intensified this effect for angiostatin but not for K5, indicating that angiostatin may be more potent in the microenvironment of tumor vasculature with decreased systemic toxicity, while K5 may inhibit neovascularization under normoxic conditions.
As it has been previously shown for angiostatin (Claesson-Welsh et al. 1998), our data provides additional evidence that the anti-angiogenic plasminogen fragments may inhibit endothelial cell migration and tube formation through a pathway related to adhesion plaque formation (T. A. Kalfa 2003).
Future goals of this project include:
- Evaluation of the changes in the cytoskeletal organization (stress fibers, lamellipodia, filopodia), adhesion plaque formation, and the effects on the Rho GTPases (Rho, Rac, and Cdc42), triggered by angiostatin and K5.
- Dissection of the signal transduction pathways possibly affected downstream the FAK (which may include PI-3-K, PKB/Akt, eNOS, mitogen-activated protein (MAP) kinases ERK-1 and ERK-2).
Related Publications
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Claesson-Welsh L, Welsh M, Ito N, Anand-Apte B, Soker S, Zetter B, O'Reilly M, Folkman J (1998) Angiostatin induces endothelial cell apoptosis and activation of focal adhesion kinase independently of the integrin-binding motif RGD. Proc Natl Acad Sci U S A 95:5579-83.
Gonzalez-Gronow M, Kalfa T, Johnson CE, Gawdi G, Pizzo SV (2003) The voltage-dependent anion channel is a receptor for plasminogen kringle 5 on human endothelial cells. J Biol Chem 278:27312-8.
T. A. Kalfa MLW, S.V. Pizzo (2003) Angiostatin and Kringle 5 Interact with Adhesion Complexes of the Human Microvascular Endothelial Cells and Induce Tyrosine Phosphorylation of Focal Adhesion Kinase. Poster presented at AACR New Directions in Angiogenesis Research Conference. Chicago, IL.
Moser TL, Stack MS, Asplin I, Enghild JJ, Hojrup P, Everitt L, Hubchak S, Schnaper HW, Pizzo SV (1999) Angiostatin binds ATP synthase on the surface of human endothelial cells. Proc Natl Acad Sci U S A 96:2811-6.
Tarui T, Miles LA, Takada Y (2001) Specific interaction of angiostatin with integrin alpha(v)beta(3) in endothelial cells. J Biol Chem 276:39562-8.
Troyanovsky B, Levchenko T, Mansson G, Matvijenko O, Holmgren L (2001) Angiomotin: an angiostatin binding protein that regulates endothelial cell migration and tube formation. J Cell Biol 152:1247-54.
For additional information, please contact Dr. Theodosia Kalfa, Division of Experimental Hematology, at 513-636-0989. Dr. Kalfa's office can be found in room 2363 of Location R (Research Foundation Building).
