Each year in Canada, around 3,000 women will be diagnosed with high grade serous ovarian cancer (HGSOC) — the most common type of ovarian cancer. Despite good responses to first line treatments for many women, it comes back as a resistant disease. Targeted treatments such as PARP inhibitors (PARPi) have made a big difference to HGSOC that is deficient in a DNA repair pathway (Homologous recombination repair), but this only benefits around 50 percent of women with HGSOC. PARPi combinations with drugs that target angiogenesis and the immune response remain under investigation. This project will investigate how chemotherapy vs. targeted therapies differentially affects the DNA damage and immune response in cancer and how effective non-chemotherapy combination treatments work, including different doses and schedules. Also, which patient might benefit from which treatment and when for example should the targeted therapies be given before or after the chemotherapy? Creating models similar to humans, we will transplant patient tumors (removed at surgery) on the skin and inside the abdomen of mice and analyze the molecular nature (at single cell level) of these tumors before/after treatment. Results of these studies will inform future clinical trials.