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Title: Elucidation of the effects of hypoxia on DNA repair machinery in brain tumour cells
Author: Cowman, S. J.
ISNI:       0000 0004 7659 0107
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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Glioblastoma (GBM) and Medulloblastoma (MB) are the most common brain tumours of adults and children respectively. These tumours are hypoxic as their oxygen levels are lower than the physiological 5-8% O2 found in the brain. Tumour hypoxia can promote tumour cell invasion, increase metastatic potential and leads to resistance to conventional cancer therapies. Chemotherapeutic agents and irradiation induce excessive DNA damage in order to overwhelm the DNA repair pathways and initiate apoptosis. This thesis aimed to examine the impact of hypoxia on DNA repair mechanisms in GBM and MB, which has not yet been reported. Hypoxic tumours are associated with poor patient outcome, in part due hypoxia-induced resistance to treatment. Work in this thesis showed that, in MB and GBM cells, chronic hypoxia was necessary to induced a resistance phenotype. Downregulation of critical components of the double strand break repair pathway was found to be responsible for treatment resistance in some, but not all hypoxic MB cells. Since hypoxia can directly influence transcription of DNA repair proteins, a NanoString assay was used to obtain a comprehensive assessment of DNA repair gene expression in multiple MB and GBM cell lines exposed to hypoxia. Moderate and severe hypoxic exposure had a variable impact on gene expression, with no clear-cut impact of different oxygen tensions. The level of transcripts of several DNA repair genes were downregulated across multiple GBM cell lines, especially LIGIV, which encodes DNA Ligase IV responsible for joining double strand breaks during DNA repair. A multiphoton laser microirradiation protocol was used to assess, in living cells, the functional impact of LIGIV downregulation. Reduced double strand break repair efficiency in hypoxia was observed, which may lead to genomic instability that drives tumour progression. Investigations into GBM and MB tumour cell biology, such as that described in this thesis, will aid in the development of new treatment methods, which are desperately needed.
Supervisor: See, Violaine Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral