Exploiting tubulin acetylation to improve response to PARPi-based cancer therapies

Primary supervisor: Susana Godinho, Queen Mary University of London

Secondary supervisor: Suzana Hadjur, UCL

Project

Project background and description:

Personalised medicine has revolutionised cancer treatment through the development of selective inhibitors that specifically target cancer cells. Some of these inhibitors are initially effective but, almost invariably, patients stop responding to treatment due to the development of resistance by the cancer cells. Therefore, understanding how to improve existing selective inhibitors that are currently used in the clinic could be a very useful strategy to improve overall survival of cancer patients.

PARP inhibitors (PARPi; e.g. Olaparib) can be very effective against tumours that lack efficient homologous recombination (HR) to repair DNA double strand breaks (DSB), e.g. breast and ovarian cancers that harbour BRCA1/2 mutations [1-2]. In the absence of HR, DSBs that result from PARP inhibition, lead to the formation of deleterious chromosome fusions, promoted by Non-Homologs End Joining (NHEJ) DNA repair pathway, and ultimately cell death. These erroneous chromosome fusions are regulated by microtubules and associated motors that promote DSB mobility inside the nucleus, although mechanisms are unclear [3]. Thus, we hypothesise that manipulating DSB mobility could improve response to PARPi by increasing abnormal chromosome fusions. We recently found that a specific microtubule posttranslational modification, acetylation, regulates DSB mobility in response to DNA damage and impacts the response to PARPi in HR-deficient cells, suggesting that changing the levels of tubulin acetylation could be used to further decrease cell viability in response to PARPi.

Here, we propose to investigate the mechanisms by which microtubule acetylation promotes DSB mobility and repair, how mobility impacts overall chromatin organisation and genomic aberrations that result from DNA damage and how we can exploit increased DSB mobility to improve response to PARPi.

Aim 1: Investigate the role of tubulin acetylation in DSB mobility We will test new hypotheses based on our recent findings [4] and live cell imaging and novel image analyses tools to monitor DSB mobility to dissect how acetylated microtubules, by promoting nuclear deformation, impact DSB mobility and repair. We are in a unique position to address this question due to our tools and novel preliminary data.

Aim 2: Dissect how DSB mobility promotes abnormal chromosome fusions Using telomere fusion as model system, we will determine the role of DSB mobility in NHEJ-mediated abnormal chromosome fusions. In addition, we will use Hi-C technology to assess how nuclear deformations and DSB mobility induced by acetylated microtubules impact chromatin organisation and the formation of structural aberrations, such as translocations, in cancer cells [5].

Aim 3: Test the efficacy of PARPi in combination with strategies that modulate tubulin acetylation levels The viability of HR-deficient cancer cells (e.g. BRCA2-/-) treated with PARPi will be assessed in conditions where tubulin acetylation is inhibited (αTAT depletion) or exacerbated (αTAT overexpression). Development of resistant clones will also be determined in these conditions. Syngeneic mouse models for breast cancer established in the lab will be used to assess tumour response to PARPi in vivo.

Candidate background

This project would suit candidates with a background in biology, and an interest in cell and tumour biology.

Potential Research Placements

1. Sarah Martin, Barts Cancer Institute, Queen Mary University of London
2. Suzana Hadjur, UCL Cancer Institute
3. TBC

References

1. Farmer et al., (2005), Nature. “Targeting the DNA repair defect in BRCA mutant cells as a therapeutic strategy”
2. Ashworth (2008), Journal Clinical Oncology. “A Synthetic Lethal Therapeutic Approach: Poly(ADP) Ribose Polymerase Inhibitors for the Treatment of Cancers Deficient in DNA Double-Strand Break Repair”
3. Lottersberger et al., (2015), Cell. “53BP1 and the LINC Complex Promote Microtubule-Dependent DSB Mobility and DNA Repair”
4. Monteiro et al., (2023), EMBO Journal. “Centrosome amplification fine-tunes tubulin acetylation to differentially control intercellular organization”
5. Barrington et al. (2019), Nature Communications. “Enhancer accessibility and CTCF occupancy underlie asymmetric TAD architecture and cell type specific genome topology”