Abstract
The induction of angiogenesis is known to play a critical role in the successful growth, invasion, and metastasis of a tumor. A tumor will not grow beyond a few cubic millimeters without the formation of its own capillary network. Several antiangiogenic agents are under investigation in the clinic setting for the treatment of cancer. Carboxyamido-triazole (CAI), an inhibitor of Ca2+-mediated signal transduction, has been previously shown to inhibit angiogenesis in vitro and in vivo and to down-regulate matrix metalloproteinase-2 in vitro. Diminished levels of intracellular Ca2+ result in decreased nitric-oxide synthase (NOS) activity and thereby inhibit the production and release of NO. The antiangiogenic activity of CAI was investigated by assessing microvessel growth from rat aortic segments and in cell culture using human aortic endothelial cells (HAECs). With these models, vascular endothelial growth factor (VEGF) and NOS production and secretion were evaluated. CAI concentrations ranging from 0.25 to 12.0 μg/ml inhibited new microvessel formation in rat aortic cultures and HAEC proliferation in a dose-dependent manner. Additionally, HAECs treated with CAI showed a dose-dependent decrease of NOS expression and a decrease in both VEGF expression and secretion. Rat aortic segments demonstrated decreased VEGF expression in situ on immunostaining. These data suggest that modulation of the NOS-NO-VEGF pathway through Ca2+-mediated signaling by CAI inhibits angiogenesis in vitro.
Footnotes
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Send reprint requests to: Dr. William D. Figg, Medicine Branch, Division of Clinical Sciences, National Cancer Institute, NIH, Bldg. 10, Room 5A01, 10 Center Dr., Bethesda, MD 20892. E-mail:wdfigg{at}helix.nih.gov
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↵1 This work was funded by the U.S. Government.
- Abbreviations:
- CAI
- carboxyamido-triazole
- NO
- nitric oxide
- NOS
- nitric-oxide synthase
- DMSO
- dimethyl sulfoxide
- EBM-II
- endothelial cell basal medium
- EGM-II
- endothelial cell growth medium
- VEGF
- vascular endothelial growth factor
- HUVEC
- human umbilical vein endothelial cell
- ecNOS
- endothelial cell nitric-oxide synthase
- HAEC
- human aortic endothelial cell
- Received May 28, 1999.
- Accepted July 26, 1999.
- U.S. Government
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