Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.778524
Title: Investigation of FANCD2 in triple negative breast cancer
Author: Almarzouq, Batool Mohammed
ISNI:       0000 0004 7964 254X
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Abstract:
Despite triple negative breast cancer (TNBC) representing between 10 % to 15 % of all breast cancers, no important therapeutic advances have been developed since the introduction of taxanes as an adjuvant therapy over 20 years ago. In order to develop novel therapies for TNBC patients, a thorough understanding of the vulnerability of components of the DNA damage response (DDR), involved in the survival and progression of the tumour, may prove advantageous. The Fanconi anaemia (FA) proteins play a crucial role in the maintenance of genome stability in the DDR, operating together with BRCA1 and BRCA2 in a pathway often referred to as the FA-BRCA pathway. A critical event in the FA pathway is the monoubiquitination of FANCD2 protein, performed by the FA core complex. Absence of any of the nine FA core complex proteins results in a lack of FANCD2 monoubiquitination. However, despite the close functional association of the FA proteins with BRCA1 and BRCA2, little is known about the status of FA gene mutations and protein expression in breast cancer. First, the frequency of alterations in the nine FA core complex genes was examined. Using a bioinformatics approach it was shown that alterations in the core complex genes are a feature of TNBC, and occur much more frequently than in less aggressive breast cancers. As the FA core complex impacts on the expression of the monoubiquitinated form of FANCD2, the status of FANCD2 monoubiquitination was then investigated in representative TNBC cell lines. It was shown that TNBC cell lines are characterized by depletion of the FANCD2 protein and exhibit a FA-like cellular phenotype. Moreover, TNBC cell lines were characterised by a lowered expression of FANCD2 in both the nuclear and cytosolic cell fractions. Building upon this, as monoubiquitinated FANCD2 (FANCD2-L) is essential for the DNA repair processes downstream in the FA pathway (including homologous recombination repair and translesion synthesis), this may present a vulnerability that could potentially be exploited using the principal of synthetic lethality for targetted therapy. Attempts were made to identify a small molecule inhibitor of a specific component of the DDR, that might be used in TNBC therapy. Targeting cells which lack FANCD2-L may represent a plausible strategy for expanding the utility of PARP inhibitors. It is shown that the loss of the monoubiquitinated form of FANCD2 in TNBC confers sensitivity to certain PARP inhibitors and complete depletion of FANCD2 sensitises TNBC cell lines to AZD1390, an ATMinhibitor. Finally, non-canonical roles for FANCD2 were investigated as little attention has been devoted to studying FANCD2's non-nuclear functions with regard to cancer pathogenesis. FANCD2 is present in different cellular compartments as determined using in silico and in vitro methods. Importantly monoubiquitinated FANCD2 was found outside the nucleus and in the mitochondria. Loss of expression of mitochondrial FANCD2-L was shown to result in mitochondrial dysfunction. It is suggested that FANCD2 may play an important role in maintaining the balance of oxidative phosphorylation and glycolysis.
Supervisor: Jones, Nigel Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.778524  DOI:
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