Ablation of microvessels in vivo upon dimerization of iCaspase-9

Abstract

Anti-angiogenic therapies based on targeted disruption of

Antiangiogenic gene therapy: disruption of neovascular networks mediated by inducible caspase-9 delivered with a transcriptionally targeted adenoviral vector

“…This was somewhat lower than we expected initially, because we had observed before that approximately 90% of the endothelial cells stably expressing iCaspase-9 undergo apoptosis upon exposure to AP20187, 9 and that about 90% of the endothelial cells were positive for b-gal when AdhVEGFR2-LacZ was used here. These puzzling findings were perhaps clarified when we performed immunostaining in endothelial cells infected with Ad-hVEGFR2-iCaspase-9 and observed that only about 48% of the cells actually expressed iCaspase-9.…”

“…[5][6][7][8] We have recently demonstrated that the direct activation of caspase-9 induces apoptosis of proliferating endothelial cells, that the endothelial cell survival factors VEGF and bFGF do not protect these cells against apoptosis, and that activated iCaspase-9 is sufficient to disrupt blood vessels in vivo. 9 These experiments established proof-of-principle data to support the concept that direct activation of a proapoptotic caspase in endothelial cells might be beneficial for the treatment of solid tumors. 9 However, the utilization of a caspase-based artificial death switch as an antiangiogenic therapeutic strategy would require that the therapeutic gene be expressed only in neovascular endothelial cells, and not expressed in mature blood vessels.…”

“…9 These experiments established proof-of-principle data to support the concept that direct activation of a proapoptotic caspase in endothelial cells might be beneficial for the treatment of solid tumors. 9 However, the utilization of a caspase-based artificial death switch as an antiangiogenic therapeutic strategy would require that the therapeutic gene be expressed only in neovascular endothelial cells, and not expressed in mature blood vessels.…”

“…15 When the catalytic domain of caspase-9 is fused to one or more CID-binding domains, the resulting fusion protein (inducible caspase-9, named iCaspase-9) can be activated with a dimerizer compound (eg AP20187) and initiate an irreversible signaling pathway that results in cell death. 9,13,17,24 In a previous report, we have characterized a stable endothelial cell line expressing iCaspase-9, and demonstrated that activation of this caspase-based artificial death switch was sufficient to induce apoptosis. 9 Here, we used a transcriptional targeting strategy to generate an adenoviral vector containing the human VEGFR2 promoter and showed that it drives expression of reporter genes primarily in neovascular endothelial cells.…”

“…9,13,17,24 In a previous report, we have characterized a stable endothelial cell line expressing iCaspase-9, and demonstrated that activation of this caspase-based artificial death switch was sufficient to induce apoptosis. 9 Here, we used a transcriptional targeting strategy to generate an adenoviral vector containing the human VEGFR2 promoter and showed that it drives expression of reporter genes primarily in neovascular endothelial cells. We showed that activation of adenovirally delivered iCaspase-9 with the dimerizer compound AP20187 activated endogenous caspase-3 and induced endothelial cell apoptosis in vitro.…”