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Ablation of microvessels in vivo upon dimerization of iCaspase-9
1Department of Cariology, Restorative Sciences and Endodontics, University of Michigan School of Dentistry, Ann Arbor, MI 48109-1078, USA.
Abstract:
Anti-angiogenic therapies based on targeted disruption of the tumor microvascular network have been proposed for cancer treatment. Inhibitors of the endothelial cell pro-survival pathway mediated by VEGF were shown to activate caspases and cause microvascular regression, but the efficacy of this strategy can be hindered by the engagement of redundant survival pathways. Alternatively, if direct activation of an apical pro-apoptotic caspase is sufficient to disrupt microvessels in vivo, such a strategy could potentially override upstream endothelial cell survival inputs and disrupt tumor neovascular networks. Here, we fused caspase-9 to a mutated FKBP12 domain to express an inducible caspase-9 molecule (iCaspase-9) that can be activated by a cell-permeable dimerizer drug, and transduced this construct into primary endothelial cells. We found that drug-induced dimerization of iCaspase-9 is sufficient to activate endogenous caspase-3 and trigger apoptosis even when endothelial cells are treated with the pro-survival factors VEGF or bFGF. A single intraperitoneal injection of the dimerizer drug induced apoptosis of endothelial cells expressing iCaspase-9 and elimination of human microvessels engineered in immunodeficient mice. These results demonstrate that the activation of iCaspase-9 disrupts microvessels in vivo, and suggest a novel anti-angiogenic strategy based on the expression and controlled activation of an inducible death gene in neovascular endothelial cells.
Insights
This study introduces an inducible caspase-9 (iCaspase-9) system to trigger endothelial cell apoptosis and disrupt tumor blood vessels. This novel anti-angiogenic therapy effectively eliminates microvessels, offering a new cancer treatment strategy.
Area of Science:
- Oncology
- Molecular Biology
- Vascular Biology
Background:
- Anti-angiogenic therapies aim to disrupt tumor neovascular networks by targeting endothelial cells.
- Existing therapies targeting VEGF pathways can be limited by redundant endothelial cell survival mechanisms.
- Directly activating apoptosis in endothelial cells may overcome survival pathway resistance.
Purpose of the Study:
- To investigate if direct activation of an apical pro-apoptotic caspase can disrupt tumor microvessels in vivo.
- To develop an inducible system for controlled apoptosis induction in endothelial cells.
- To assess the anti-angiogenic potential of an inducible caspase-9 (iCaspase-9) system.
Main Methods:
- A fusion protein of caspase-9 and a mutated FKBP12 domain (iCaspase-9) was created.
- The iCaspase-9 construct was transduced into primary endothelial cells.
- Drug-induced dimerization of iCaspase-9 was used to trigger apoptosis, even with pro-survival factors (VEGF, bFGF).
- The system's efficacy was tested in vivo using human microvessels in immunodeficient mice.
Main Results:
- Drug-induced dimerization of iCaspase-9 successfully activated caspase-3 and induced apoptosis in endothelial cells.
- Apoptosis occurred despite the presence of pro-survival factors like VEGF and bFGF.
- A single injection of the dimerizer drug led to the elimination of iCaspase-9 expressing endothelial cells and human microvessels in mice.
Conclusions:
- Activation of iCaspase-9 is sufficient to induce endothelial cell apoptosis and disrupt microvessels in vivo.
- This inducible system offers a potential strategy for targeted anti-angiogenesis.
- Controlled activation of an inducible death gene in neovascular endothelial cells presents a novel therapeutic approach for cancer treatment.