Figure 2.

EGFR* induction cooperates with conditional Ink4a/Arf and Pten deletions to induce malignant glioma formation. A, schematic of inducible EGFR* allele under regulation of human GFAP promoter element. B, EGFR* induction was efficiently repressed by Dox administration. Brain tissue lysates were prepared from littermate single- or bi-transgenic mice maintained on- (+) or off- (−) Dox and subjected to immunoblot analysis for EGFR and Actin. C, Kaplan-Meier brain tumor-free survival analysis of tamoxifen-treated mouse cohorts consisting of tetO-EGFR* cInk^L cPten^L (iEIP) maintained off-Dox (n = 25), tetO-EGFR* cInk^L cPten^L (iEIP) on-Dox (n = 5), tetO-EGFR* cInk^L (iEI) off-Dox (n = 6), tetO-EGFR* cPten^L (iEP) off-Dox (n = 5), tetO-EGFR* (iEGFR) off-Dox (n = 7), and cInk^L cPten^L (cIP) off-Dox (n = 8). D, iEIP gliomas displayed high mitotic indices and low levels of apoptosis. H&E and IHC staining against Ki67 and activated Caspase-3 (Act-Cas3) were performed using sections from normal mouse brains or iEIP malignant gliomas. E, sections of normal mouse brain tissue or iEIP tumors were stained with antibodies against Pten and EGFR. The arrow heads point to embedded Pten-positive endothelial cells in the tumors. F, shown are representative images of IHC staining against phosphorylated Akt (p-Akt), Mapk (p-Mapk) and Stat3 (p-Stat3) performed on sections from normal mouse brains and iEIP malignant gliomas. Scale bars represent 50 μm.