http://bura.brunel.ac.uk/handle/2438/32871 Mon, 29 Jun 2026 17:33:33 GMT 2026-06-29T17:33:33Z http://bura.brunel.ac.uk/handle/2438/33502 Title: Telomere length elongation by epigenetic modifier drugs: A potential mechanism by which cancer develops chemo-resistance Authors: Al-dulaimi, Sarah Abstract: Telomeres are specialised structures localized at the ends of eukaryotic linear chromosomes. Telomeres play an important role in protecting chromosome ends by preventing the activation of DNA damage response (DDR). In normal cells, telomeres become shorter with each cell division, which eventually leads to cellular senescence. Cancer cells, avoid telomere shortening by activating mechanisms that maintain telomere lengths. Most normal cells reach replicative senescence after 90 population doublings and then enter telomere crisis. This suggest that many premalignant cells lose their ability to keep dividing before they can accumulate additional mutations. Two mechanisms are known: telomerase reactivation and alternative lengthening of telomere (ALT). 80% -85% of cancer cells activates telomerase. The telomerase enzyme consists of two subunits, telomerase reverse transcriptase (TERT) and telomerase RNA (TR). ALT is active in around 15-20 % of cancer cells and maintains telomere lengths via alternative lengthening of telomere via homologous recombination. A common feature of ALT-positive human cells is the presence of C-circles and promyelocytic leukemia (PML) nuclear bodies (ALT-associated PML (APBs)). POLD3, a subunit of DNA polymerase has also been shown to be essential for ALT activity. The hypomethylating drug 5-aza-2′-deoxycytidine (5-aza) is widely used in the treatment of haematological malignancies. Moreover, cancer cells rapidly become resistant to the drug, leading to relapse. The study presented in this thesis investigated the short term (72 h) and long term (over one month) effects of 5-aza on telomere biology in breast cancer cells, with a focus on ALT activity and POLD3 expression. Telomere maintenance mechanisms were investigated using qPCR, c-circle and TRAP assays. The TIF (Telomere dysfunction induced foci) was used to detect DNA damage at telomeres and immunofluorescence for the detection of ALTassociated PML. POLD3 gene expression was quantified using qPCR and western blotting. Short-term 5-aza treatment modestly altered telomerase activity while significantly promoting ALT activation, which was accompanied by increased expression of POLD3. Silencing of POLD3 using siRNA in 5-aza treated cells resulted in telomere shortening. Long-term exposure to 5-aza led to the development of drug resistance, with cells acquiring the ability to proliferate at higher concentrations of 5-aza, and reduced sensitivity to doxorubicin, alongside increased migratory capacity. However, resistant cells exhibited enhanced sensitivity to radiotherapy. Collectively, our findings demonstrate that low-dose (10 uM) and prolonged exposure to 5- aza promotes ALT- dependent telomere maintenance through POLD3 upregulation, contributing to cancer cell survival and therapeutic resistance. These findings identify a novel mechanism by which cancer cells develop resistance to epigenetic therapy and also highlight telomere maintenance pathways as promising targets to improve treatment outcomes. Resistance to 5-aza significantly compromises the efficacy of combination therapies, including those involving chemotherapy and radiotherapy Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London Wed, 01 Jan 2025 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/33502 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/33499 Title: Dysregulation of sphingolipid-metabolizing enzymes in Friedreich’s ataxia: In vitro and in vivo insights into therapeutic targeting Authors: Ramchunder, Z; Kalef-Ezra, E; Suleman, S; Edzeamey, FJ; Szunyogh, S; Gittins, O; Mena, NC; Wade-Martins, R; Valle, A; Pourzand, C; Anjomani Virmouni, S Abstract: Friedreich’s ataxia (FRDA) is an inherited neurodegenerative disorder caused by a GAA repeat expansion within the FXN gene, leading to reduced frataxin levels. This deficiency results in mitochondrial dysregulation, oxidative stress, and progressive cell death. Currently, only one approved treatment exists for FRDA in the United States, Canada, and the European Union, which improves neurological outcomes but has not been fully evaluated for broader disease symptoms. Therefore, identifying new therapeutic targets remains essential. Sphingolipids are increasingly recognized for their roles in neurodegeneration with emerging evidence indicating their dysregulation in FRDA. Here, we investigate whether sphingolipid-metabolizing enzymes are similarly affected and assess the therapeutic potential of targeting them. Our findings demonstrate that these enzymes are dysregulated across multiple FRDA models. Importantly, their modulation in vitro and in vivo significantly reduces mitochondrial dysfunction, enhances frataxin expression, and improves key pathological features of the disease, highlighting sphingolipid metabolism as a promising therapeutic target for FRDA. Description: Data and code availability: • All data reported in this paper will be shared by the lead contact upon request. • This paper does not report original code. • Any additional information required to reanalyze the data reported in this paper is available from the lead contact upon request. Mon, 22 Jun 2026 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/33499 2026-06-22T00:00:00Z http://bura.brunel.ac.uk/handle/2438/33413 Title: Evaluating genetic liability in hypertension and stroke using machine learning and traditional statistical models: Insights from UK biobank studies Authors: MacCarthy, Gideon Abstract: Stroke is one of the leading causes of death and disability worldwide, with hypertension being a major risk factor for stroke. According to the World Stroke Organisation Global Stroke Fact Sheet, hypertension alone is responsible for over half of all stroke-related deaths and disability-adjusted life years (DALYs). While conventional risk factors for both diseases are well established, the added prediction value of genetic liability remains less clear. The traditional risk prediction models for hypertension and stroke, such as the Framingham Hypertension Risk Score (FHRS) and the Framingham Stroke Risk Score (FSRS), typically rely on clinical and demographic factors, often assume linear effects, and typically overlook genetic liability and complex interactions between predictors. In this thesis, three complementary studies were conducted to examine whether genetic liability could enhance the classification of hypertension and the prediction of strokes via both machine learning (ML) and traditional modelling techniques using data from more than 116,000 participants with European ancestry in the UK Biobank. Genetic variants and their effects obtained from genome-wide association studies were used to construct genetic liabilities for selected cardiovascular disease (CVD) risk factors and stroke, respectively. Multiple predictive models, such as Cox proportional hazards, penalized regression models (both logistic and Cox), tree-based algorithms (random forest, gradient boosting, and decision trees), and neural networks, were assessed after participants were randomly divided into training and testing sets. Discrimination (AUC), calibration, and reclassification indices (NRI, IDI, and Brier score) were used to evaluate the models. Incorporating the genetic liabilities resulted in modest but steady improvements across the studies. The genetic liabilities associated with lipids improved the classification of hypertension best with AUC using random forest. Additionally, stroke genetic liability enhanced stroke prediction with the Cox models, outperforming machine learning models. Among hypertensive individuals, the model's predictive performance (AUC) was higher in men and older adults than in women or younger adults. The Cox models outperformed all the machine learning models. Though ML methods allow for the investigation of non-linearities and interactions. Overall, genetic liability slightly enhances classification and risk prediction. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London Wed, 01 Jan 2025 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/33413 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/33249 Title: Immune dysregulation in tuberculosis-diabetes comorbidity: mechanistic and translational insights Authors: Saula, AY; Cevik, M; Cliff, JM; Ronacher, K; Bowness, R Abstract: Background: Tuberculosis (TB) remains a leading cause of infectious disease mortality worldwide, and the rising prevalence of diabetes mellitus (DM) represents a major obstacle to TB control. DM increases susceptibility to TB, worsens disease severity, delays treatment response, and is associated with poorer outcomes, largely through disruption of host immunity. Methods: We conducted a systematic review of studies published between 1974 and May 31, 2023 that examined immunological mechanisms through which DM alters TB pathogenesis. In total, 81 eligible studies involving animal models, human participants, or combined approaches were identified and synthesised across different stages of TB. Results: Across studies, DM was associated with broad dysregulation of innate and adaptive immune responses, altered cytokine signalling, impaired granuloma structure and function, and reduced control of Mycobacterium tuberculosis (Mtb). Distinct immune profiles emerged between TB disease with DM and latent TB infection with DM, with heterogeneity partly explained by differences in study design, metabolic status, and disease stage. Importantly, emerging evidence indicates that pre-diabetes and intermediate hyperglycaemia may also compromise TB immunity and contribute to disease progression. Conclusion: Our findings highlight DM as a key immunometabolic modifier of TB pathogenesis. They also suggest that earlier metabolic optimisation and hostdirected therapeutic strategies could be explored as potential approaches to improve outcomes in this growing high-risk TB-DM population. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023431040. Description: Data availability statement: The data analyzed in this study is subject to the following licenses/restrictions: The datasets can be shared with researchers upon request. Requests to access these datasets should be directed to Aminat Y. Saula, ays27@bath.ac.uk.; Supplementary material: The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fimmu.2026.1803046/full#supplementary-material . Thu, 23 Apr 2026 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/33249 2026-04-23T00:00:00Z