ap20187 and Neoplasms

Topics: Aging; Animals; Apoptosis; Cell Division; Cell Transformation, Neoplastic; Cellular Senescence; Cytokines; Disease Susceptibility; Genes, p16; Genes, Tumor Suppressor; Humans; Mice; Models, Biological; Neoplasms; Oncogenes; Tacrolimus; Tumor Suppressor Protein p14ARF

Antiangiogenic therapies have shown varying results partly because each tumor type secretes a distinct panel of angiogenic factors to sustain its own microvascular network. In addition, recent evidence demonstrated that tumors develop resistance to antiangiogenic therapy by turning on alternate angiogenic pathways when one pathway is therapeutically inhibited. Here, we test the hypothesis that expression of a caspase-based artificial death switch in tumor-associated endothelial cells will disrupt tumor blood vessels and slow down tumor progression irrespective of tumor type. Adenoviral vectors expressing inducible Caspase-9 (iCaspase-9) under transcriptional regulation with the endothelial cell-specific vascular endothelial growth factor receptor-2 (VEGFR2) promoter (Ad-hVEGFR2-iCaspase-9) induced apoptosis of proliferating human dermal microvascular endothelial cells (HDMECs), but not human tumor cells (UM-SCC-17B, head and neck squamous cell carcinoma; HepG2, hepatocellular carcinoma; PC-3, prostate adenocarcinoma; SLK, Kaposi's sarcoma; MCF-7, breast adenocarcinoma). Notably, apoptosis was dependent upon activation of iCaspase-9 with the dimerizer drug AP20187. Local delivery of Ad-hVEGFR2-iCaspase-9 followed by intraperitoneal injection of AP20187 ablated tumor microvessels and inhibited xenografted tumor growth in all tumor models evaluated here. We conclude that a cancer gene therapy strategy based on a transcriptionally targeted viral vector expressing an inducible caspase allows for selective and controlled ablation of microvessels of histopathologically diverse tumor types.

Topics: Adenoviridae; Animals; Apoptosis; Caspase 9; Cell Line; Cell Line, Tumor; Endothelial Cells; Flow Cytometry; Genetic Therapy; Genetic Vectors; Humans; Mice; Mice, SCID; Neoplasms; Neovascularization, Pathologic; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; Tacrolimus; Transcription, Genetic; Vascular Endothelial Growth Factor Receptor-2; Xenograft Model Antitumor Assays

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.

Topics: Animals; Apoptosis; Caspase 3; Caspase 9; Caspases; Cell Line; Dimerization; Endothelial Growth Factors; Endothelium, Vascular; Enzyme Activation; Enzyme Precursors; Fibroblast Growth Factor 2; Genetic Therapy; Genetic Vectors; Humans; Injections, Intraperitoneal; Lymphokines; Mice; Mice, SCID; Microcirculation; Models, Animal; Neoplasms; Neovascularization, Pathologic; Retroviridae; Tacrolimus; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors