Development of a drug profiling platform for patient-derived ovarian tumour cultures

Abstract

High grade serous ovarian cancer (HGSOC) is a deadly subtype of ovarian cancer, with no substantial change in overall survival for several decades. The advent of PARP inhibitors represents a major advance, and is now first-line therapy for patients with BRCAmutant tumours. However, there is a large proportion of HGSOC patients who are unlikely to benefit from PARP inhibitors; therefore, new therapeutic strategies are required to treat this disease. To enhance the development of new HGSOC therapies, improved pre-clinical models of the disease are needed. Here, I have utilised a living biobank of ovarian ex vivo tumour cultures, termed ovarian cancer models (OCMs), which exhibit the main hallmarks of HGSOC and show extensive genomic instability. I aimed to evaluate the OCMs as a resource for drug discovery studies, and develop a drug profiling platform using these cultures. I performed cell fate profiling on a panel of OCM cultures, revealing heterogeneity in cell culture dynamics that correlated with metrics of genomic instability. Furthermore, I subsequently established a timelapse microscopy drug profiling assay that monitors cell proliferation of OCM cultures using a nuclear-counting approach. I demonstrated the utility of this assay by screening a panel of OCMs to established HGSOC drugs, paclitaxel and cisplatin, and compared these drug sensitivities to both clinical and transcriptomic data associated with each OCM. The development of the drug profiling platform then allowed exploration of novel combination strategies. Replication stress represents a targetable oncogenic vulnerability in HGSOC. Thus, using the OCM drug profiling platform, I aimed to pharmacologically exploit replication stress by combining replication stress inducing drugs. I utilised a multiple low dose approach, which involves targeting signalling pathways with multiple drugs at low doses, to screen a panel of OCMs against the combination of ATR, CHK1, PARG and WEE1 inhibitors. This induced a potent anti-proliferative effect in the majority of OCM cultures tested, including cultures that exhibit PARP inhibitor resistance, indicating that multiple low dose therapy may present an alternative to PARP inhibitor therapy. The screen also identified that low dose dual combination of ATR and CHK1 inhibitors was strongly synergistic, with further mechanistic exploration revealing that ATR-CHK1 inhibitor combination induces replication catastrophe and post-mitotic cell death. Taken together, the OCM drug profiling platform can be used to identify novel combination therapies for HGSOC, and to interrogate the mechanistic detail of such combinations.

Date of Award	25 May 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gordon Jayson (Co Supervisor) & Stephen Taylor (Main Supervisor)