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Title: DNA-dependent protein kinase as a therapeutic target in chronic lymphocytic leukaemia
Author: Junge, Gesa
ISNI:       0000 0004 7654 3925
Awarding Body: University of Newcastle upon Tyne
Current Institution: University of Newcastle upon Tyne
Date of Award: 2015
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The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) functions in the non- homologous endjoining (NHEJ) pathway of DNA double strand break (DSB) repair and is overexpressed and/or highly active in several cancers, including chronic lymphocytic leukaemia (CLL). CLL treatment options have improved substantially, however, prognosis remains poor for patients with mutations in TP53, or with dysfunctional ataxia telangiectasia mutated kinase (ATM), a key protein in the homologous recombination repair (HRR) pathway of DSB repair. Pharmacological inhibitors of DNA-PKcs have been shown to sensitise CLL cells to DNA damaging drugs ex vivo. In this thesis, DNA-PKcs was further explored as a therapeutic target in CLL using a novel, highly selective inhibitor of DNA-PKcs (NDD0004). NDD0004 sensitised HCT116 cells, but not DNA-PK-deficient HCT116 cells, to etoposide and mitoxantrone. Mechanistic studies showed that NDD0004 prevents NHEJ activity in vitro. Chemosensitisation to mitoxantrone was also observed in primary CLL samples ex vivo in viability and apoptosis assays. Chemosensitisation was highly variable (median 49-fold with NDD0004, range 1-2000-fold) but occurred in 80% of samples, including those from poor prognosis patients. When co-cultured with CD40L-expressing fibroblasts, CLL cells began to proliferate, but became resistant to mitoxantrone-induced apoptosis. There was little evidence of chemosensitisation by NDD0004 on healthy donor lymphocytes or bone marrow cells, indicating a potential therapeutic window for the clinical use of DNA-PKcs inhibitors. It was hypothesised that ATM-deficient CLL cells or cell lines would be sensitive to DNA-PKcs inhibition due to a synthetic lethal interaction between the loss of both DSB repair pathways, however, this was not the case in four cell line pairs tested. This work has characterised a novel DNA-PKcs inhibitor, and contributed to the understanding of the therapeutic benefits and limitations of targeting DNA-PKcs in cancer therapy.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available