Mesenchymal high-grade glioma is maintained by the ID-RAP1 axis
Francesco Niola, … , Antonio Iavarone, Anna Lasorella
Francesco Niola, … , Antonio Iavarone, Anna Lasorella
Published December 17, 2012
Citation Information: J Clin Invest. 2013;123(1):405-417. https://doi.org/10.1172/JCI63811.
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Research Article Oncology

Mesenchymal high-grade glioma is maintained by the ID-RAP1 axis

Abstract

High-grade gliomas (HGGs) are incurable brain tumors that are characterized by the presence of glioma-initiating cells (GICs). GICs are essential to tumor aggressiveness and retain the capacity for self-renewal and multilineage differentiation as long as they reside in the perivascular niche. ID proteins are master regulators of stemness and anchorage to the extracellular niche microenvironment, suggesting that they may play a role in maintaining GICs. Here, we modeled the probable therapeutic impact of ID inactivation in HGG by selective ablation of Id in tumor cells and after tumor initiation in a new mouse model of human mesenchymal HGG. Deletion of 3 Id genes induced rapid release of GICs from the perivascular niche, followed by tumor regression. GIC displacement was mediated by derepression of Rap1gap and subsequent inhibition of RAP1, a master regulator of cell adhesion. We identified a signature module of 5 genes in the ID pathway, including RAP1GAP, which segregated 2 subgroups of glioma patients with markedly different clinical outcomes. The model-informed survival analysis together with genetic and functional studies establish that ID activity is required for the maintenance of mesenchymal HGG and suggest that pharmacological inactivation of ID proteins could serve as a therapeutic strategy.

Authors

Francesco Niola, Xudong Zhao, Devendra Singh, Ryan Sullivan, Angelica Castano, Antonio Verrico, Pietro Zoppoli, Dinorah Friedmann-Morvinski, Erik Sulman, Lindy Barrett, Yuan Zhuang, Inder Verma, Robert Benezra, Ken Aldape, Antonio Iavarone, Anna Lasorella

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Figure 6

Active RAP1 rescues the loss of iGIC adhesion caused by Id ablation.

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Active RAP1 rescues the loss of iGIC adhesion caused by Id ablation. (...
(A) Immunostaining for Rap1GAP (red) of representative tumor lesions in Id-cTKO mice treated with tamoxifen or oil and sacrificed 6 weeks after stereotaxic injection of Ras-V12-IRES-Cre-ER-shp53 lentivirus. Nuclei were counterstained with DAPI (blue). Scale bars: 100 μm. (B) Two hundred glioma spheres from Id1L/LId2L/LId3L/L iGICs coinfected with lentiviral vectors expressing EGFRvIII-IRES-Cre-ER-shp53 and pLOC-RAP1A-G12V;Q63E-GFP or pLOC-GFP were treated with vehicle (control [CTR]) or 4-OHT for 4 days and assayed for adhesion to brain-derived endothelial cells for 24 hours. Scale bars: 100 μm. (C) Quantification of the percentage of glioma spheres from B adhering to a monolayer of brain endothelial cells after an adhesion period of 24 hours, as determined by fluorescent microscopy review. Data represent the mean ± SD of quadruplicate samples. *P = 0.00184, vector/control vs. vector/4-OHT; #P = 0.00524, vector/4-OHT vs. RAP1AG12V;Q63E/4-OHT. (D) Id1L/LId2L/LId3L/L iGSCs coinfected with lentiviral vectors expressing EGFRvIII-IRES-Cre-ER-shp53 and pLOC-RAP1A-G12V;Q63E-GFP or pLOC-GFP were treated with vehicle or 4-OHT for 4 days. Gliomaspheres were dissociated, and single cells were plated at density of <1 cell per μl in 96-well plates in triplicates. The number of gliomaspheres was scored 10 days later. Data represent the mean ± SD. *P = 1.541 × 10–6, vector/control vs. vector/4-OHT; #P = 9.6489 × 10–5, vector/4-OHT vs. RAP1AG12V;Q63E/4-OHT.