Surgery (RMH) - Theses
Permanent URI for this collection
Search Results
1 - 1 of 1
-
ItemGlioma stem cells: novel signalling pathways and potential therapeutic advances( 2013)High grade glioma continues to portend a dismal prognosis for patients, despite ongoing, albeit incremental, advances in surgery, irradiation and chemotherapy. This has necessitated an overhaul in the understanding of disease pathogenesis, and the search for a superior model for screening of small molecule therapeutic agents, especially in light of the poor translational outcomes generated from work on traditional, serum-fed, glioma cell lines. The cancer stem cell hypothesis has revolutionised neuro-oncological research, and the discovery of the glioma stem cell (and in particular, its characteristic in vitro gliomasphere-producing qualities) has led to new avenues of thinking, in terms of glioma proliferation, invasiveness and mechanisms of chemo- and radioresistance. Coupled with this has been further characterisation of the genetic constitution of high grade gliomas, which show Pi3k-related aberrations in up to 90% of such lesions, related mainly to EGFR amplification, EGFRvIII expression and PTEN mutation. This study has led to the production of sixteen gliomasphere-producing (or glioma stem cell) clones, from the collection of sixty-six individual specimens, which included lower grade lesions. It was confirmed that this set of stem cell lines exhibited all of the trademark characteristics of a tumour stem cell, characterised by a potential for self-renewal, pluripotency, proliferation, and tumour formation upon xenograft transplantation. Western blot analysis confirmed that thirteen of the sixteen reproducible stem cell clones demonstrated hyperphosphorylated Akt. This led to an investigation of suitable Pi3k inhibitors via a series of in vitro lactate dehydrogenase cytotoxicity assays, which showed that the N10-substituted phenoxazine, Akt inhibitor Akt X, was the only agent which demonstrated effective in vitro cytotoxic potential against glioma stem cells. Interestingly, Akt X was shown to be more efficacious against those glioma stem cell clones which failed to express PTEN protein on Western blot analysis, and this result was found to be statistically significant. Further in vitro LDH cytotoxicity assays revealed glioma stem cells were largely resistant to conventional irradiation and temozolomide, but this was reversed by Akt X, confirming this agent’s potential as a successful stem cell-specific agent in the clinical management of high grade glioma patients. Extensive exome sequencing analysis confirmed the presence of a number of genetic variants in the glioma stem cell clones, whose putative effect and expression concerns signalling pathways not commonly reported in conjunction with gliomagenesis in the past, including the WNT/-catenin and SWH pathways. Western blot analysis and immunohistochemistry demonstrated that the glioma stem cell clones overexpress YAP, a protein whose activation is normally suppressed via the intact SWH pathway, identifying it as a prospective, glioma stem cell-specific oncoprotein, and target for future development in pharmacotherapeutics.