Proliferating tissues, including embryonic and tumour tissues, preferentially employ aerobic glycolysis to support cell growth. This reliance on glycolysis even in the presence of oxygen, referred to as the “Warburg Effect”, may confer a proliferative, survival and invasive advantage and be exploited therapeutically. In this thesis, we demonstrate that the glycolytic enzyme Hexokinase 2 (HK2) is crucial for the “Warburg Effect” in human Glioblastoma Multiforme (GBM), the most common and therapeutically resistant malignant brain tumour. In contrast to normal brain and low-grade gliomas, GBMs exhibited a marked increase in HK2 expression, but not HK1, particularly in perinecrotic, hypoxic regions and its expression predicted poor overall survival of GBM patients. Stable loss of HK2 in GBM cells restored oxidative phosphorylation (OXPHOS)-mediated glucose metabolism, with increased oxygen consumption and decreased lactic acid production, an effect not seen with loss of glycolytic enzymes HK1 or PKM2. Furthermore, HK2 depletion resulted in decreased proliferation in vitro and in vivo and increased sensitivity to apoptotic inducers such as radiation and chemotherapy, both common adjuvant therapies of GBMs. Intracranial xenografts of GBM cells with reduced HK2 demonstrated significantly increased survival with decreased proliferation and angiogenesis yet enhanced invasiveness. In contrast, exogenous HK2 expression in GBM cells promoted proliferation, therapeutic resistance and intracranial growth. This was dependent partly on the PI3K/AKT dependent translocation of HK2 to the mitochondrial membrane. Stable loss of glycolytic enzymes HK2, HK1 and PKM2 reduced GBM proliferation but differentially altered the PI3K/AKT/mTOR and AMPK signaling pathways, the extent to which may influence whether a cell preferentially undergoes autophagy or apoptosis as the primary mode of cell death. Collectively, targeting enzymes employed by the tumour to modulate its energy metabolism, such as HK2 in GBMs, may favourably alter its therapeutic sensitivity to radiation and both classical and novel chemotherapeutic agents.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/26339 |
| Date | 23 February 2011 |
| Creators | Wolf, Amparo |
| Contributors | Guha, Abhijit |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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