Glioblastoma is the most common and aggressive malignant brain disease with an invariably poor prognosis. The typical multimodality treatment for glioblastoma includes surgery, ionizing radiation and cytotoxic chemotherapy, usually with temozolomide. However, due to the resistance to radiation and chemotherapy as well as the tendency of this tumor to relapse, patients with glioblastoma are rarely curable, which highlight the urgent need for more intensive research and more effective targeted glioblastoma therapeutics. Recent studies suggest that relapse occurs because glioblastoma stem cells (GSC) are not eradicated by conventional therapies.
Identification of GSC targets for drug discovery is limited by the challenges of isolation, characterisation and maintenance of GSCs. We hypothesize that a model of GSCs could be derived from pluripotent stem cells engineered with appropriate mutations, to produce a clean and unlimited supply of GSCs for drug discovery.
We are using tissue from “floxed” pik3ca/PTEN engineered mice (REF) as a source of iPSCs. A Cre-excisable Dox-inducible polycistronic OKSM lentivirus was validated using an Oct4-GFP reporter to detect reprogramming of mouse embryonic fibroblasts and this method is now being applied to generate iPS cells from the transgenic mice. These iPSCs will be subsequently used to derive neural stem cells (NSCs) and then the GSC model will be activated by inducing expressing of Cre-recombinase using tamoxifen, to excise the floxed PTEN and to activate Pik3caH1047R. The established GSC model will be investigated using proteomics techniques (SILAC) to determine protein phosphorylation downstream of PI3K signalling. Our primary objective is to identify phosphorylated proteins, downstream of PI3K, which may be new targets for suppression of GSC activity. The iPSC source has the potential to provide a valuable purer population of GSC for basic research of glioblastoma as well as drug discovery.