Thesis Format
Monograph
Degree
Master of Science
Program
Anatomy and Cell Biology
Supervisor
Parsyan, Armen
2nd Supervisor
Allan, Alison L.
Co-Supervisor
Abstract
The triple negative breast cancer (TNBC) subtype confers the poorest prognosis and oncological outcomes. Cancer resistance to radiotherapy is one of the factors underlying poor responses in TNBC. Our laboratory previously demonstrated that radiotherapy in combination with the polo-like kinase 4 (PLK4) inhibitor, CFI-400945, led to synergistic anticancer effects in TNBC models. In this thesis, we explored the potential mechanisms of these anticancer effects in-vitro. We assessed alterations in key proteins participating in DNA-damage responses using immunoblotting and immunohistochemistry, perturbations of cell cycle regulations using flow cytometry, and alterations in the gene expression landscape using transcriptomics. We identified that the combination treatment leads to distinct cell cycle changes, such as G2/M arrest and increased polyploidy, as well as enrichment in various cellular pathways, including ones related to cell death, cell cycle and DNA repair. These results create a solid foundation for further studies of the anticancer mechanisms of CFI-400945 and radiotherapy.
Summary for Lay Audience
Breast cancer is a common disease among women worldwide and it can be categorized into different subtypes. The triple negative breast cancer (TNBC) subtype has the worst prognosis and survival outcomes. A common treatment for TNBC patients is radiotherapy, but sometimes patients can develop resistance to radiation. Currently, combination treatments of radiation with drugs are used in many cancers but are lacking in breast cancer. CFI-400945 is a new anti-breast cancer drug that targets a protein called polo-like kinase 4 (PLK4), which is involved in regulating cancer growth. Previous work in our laboratory has demonstrated that radiation in combination with CFI-400945 had a greater anticancer effect than each treatment alone. However, it is unclear exactly how and why this occurs. To understand the anticancer mechanisms of the combination treatment, I used breast cancer cell lines and treated them with CFI-400945 and/or radiation. I then investigated changes in the cell cycle, alterations in the expression of genes as well as changes in the location and expression of DNA damage response proteins. I observed that cells treated with the combination therapy arrested in the G2/M phase of the cell cycle, had an increase in polyploidy (more than four copies of the genome) and showed altered expression in genes as well as pathway changes related to immune signalling, cell cycle control, DNA repair and cell death. Firstly, G2/M arrest prevents cancer cell division and can cause a delay in DNA damage repair. Polyploidy leads to abnormal cell cycle progression, which can initiate cancer cell death or cell cycle arrest. Furthermore, the altered expression of genes as well as pathway changes involved in immune signalling, cell cycle, DNA repair and cell death suggests that they could potentially be responsible for the anticancer effects of the combination treatment. However, further analysis and greater statistical power are needed to confirm these findings. To conclude, understanding how the combination of CFI-400945 and radiation causes breast cancer cell death will help support the clinical use of this combination, which will overall help improve outcomes in breast cancer patients in the future.
Recommended Citation
Athwal, Harjot, "Studies of Anticancer Mechanisms of CFI-400945, Radiation and its Combination in Triple Negative Breast Cancer" (2024). Electronic Thesis and Dissertation Repository. 10329.
https://ir.lib.uwo.ca/etd/10329