Anaam, Emad Abduljalil Abdulghani 
ORCID: 0000-0002-8702-4376
(2021)
Investigation of the molecular basis for p53-mediated metabolic regulation in head and neck cancer.
PhD thesis, University of Liverpool.
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Abstract
Reprogramming energy metabolism, also known as the Warburg effect, has received considerable attention recently as a potential therapeutic target to improve the low survival outcomes of Squamous Cell Carcinoma of the Head and Neck (SCCHN). New evidence has demonstrated that loss-of-function mutations in TP53, the most commonly mutated gene in SCCHN, promotes the Warburg effect, but how this is mediated is unknown. The aims of this thesis were primarily to use a panel of SCCHN cell lines with defined p53 status (including two sets of isogenic cell lines) and microplate-based extra-cellular oxygen and proton flux analysis to examine in detail whether the exhibited metabolic phenotype is determined by the status of p53. Secondary aims were to investigate the mechanism that underlies this role of p53 which could lead to the identification of novel potential therapeutic strategies for SCCHN. RNAi and plasmid transfection were used to manipulate the expression of TIGAR (TP53-inducible glycolysis and apoptosis regulator), a potential target mediator of the p53-responsive cellular machinery that regulates glucose metabolism, to try to identify the role that TIGAR play in the Warburg effect with respect to changes in metabolic phenotype and sensitivity to potential therapeutic agents. Metabolic profiling of SCCHN cells using microplate-based extra-cellular oxygen consumption and acidification measurements have shown that wild type TP53 SCCHN cells display higher oxygen consumption rates (OCR) compared to cells harbouring mutant TP53, while cells harbouring mutant TP53 showed significantly higher extracellular acidification rates (ECAR) in comparison to wild type TP53 cells. This indicates that the p53 status is a dominant determinant of metabolic reprogramming in SCCHN. My results also show that although TIGAR knockdown promotes glycolytic functions in wild type p53 cells, it promotes both mitochondrial and glycolytic functions in p53-null cells, but not in mutant p53 cells, which may suggest an alternative mechanism or a possible role of gain of function (GOF) that regulates the role of TIGAR in the absence of wild type p53. In addition, although TIGAR knockdown shows no significant change in the balance between glycolysis and mitochondrial respiration in p53-null and mutant p53 cells, it changes the balance towards aerobic glycolysis in wild type p53 cells, which indicates that the TIGAR role in the metabolic switch toward glycolysis is primarily regulated by p53. I also found that TIGAR-knockdown-mediated increase in glycolysis results in sensitising the wild type p53 SCCHNs to radiotherapy. Thus, it is plausible to speculate that identifying TIGAR inhibitors may prove to be a beneficial approach to treatment in the future.
| Item Type: | Thesis (PhD) |
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| Uncontrolled Keywords: | p53, Cancer, Glycolysis, Oxidative phosphorylation, Metabolism, Head and neck cancer |
| Divisions: | Faculty of Health and Life Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 29 Mar 2022 13:40 |
| Last Modified: | 18 Jan 2023 21:12 |
| DOI: | 10.17638/03148927 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3148927 |
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