Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Anatomy and Cell Biology

Supervisor

Shepherd, Trevor G.

Abstract

Epithelial ovarian cancer (EOC) is the most lethal gynaecological malignancy in the developed world. EOC metastasis is unique since malignant cells detach directly from the primary tumor site into the abdominal fluid and form multicellular aggregates, called spheroids, that possess enhanced survival mechanisms while in suspension. As such, altered cell adhesion properties are paramount to EOC metastasis with cell detachment from the primary tumor, dissemination as spheroids, and reattachment to peritoneal surfaces for secondary tumor formation. These interactions play a crucial role in cell-cell and cell-extracellular matrix interactions, having implications in multiple steps of cancer progression. We previously showed that the CRISPR-ablation of Liver Kinase B1 (LKB1) or its downstream effector Nua Kinase 1 (NUAK1) resulted in spheroid disaggregation in vitro and is required for efficient EOC metastasis in mouse tumor cell xenografts. Global gene expression analysis demonstrated a coordinated reduction in b5-integrin (encoded by ITGB5 gene). Integrins are a family of cell-adhesion receptors required to mediate cellular interactions with the extracellular matrix (ECM) and promote tumorigenesis in various malignancies; however, the role of b5-integrin in EOC is unknown. Using publicly-available datasets and western blot analysis, we identified relatively high b5 integrin expression in established and patient ascites-derived EOC cell lines. siRNA-mediated knockdown of ITGB5 reduced EOC cell adhesion, impacted adherent cell and spheroid viability. We identified that b5 integrin is required for efficient spheroid reattachment and subsequent cell spreading. When evaluating the interaction of b5 integrin with ECM ligands, results indicate that b5 integrin and its association with vitronectin may play a role in spheroid reattachment.

Summary for Lay Audience

Epithelial ovarian cancer is one of the most lethal gynaecological cancers in the developed world and most individuals are diagnosed at advanced stages. When ovarian cancer cells spread, a process called metastasis, the cancer cells try to survive starvation-like conditions by forming cell clusters called spheroids. During this time, ovarian cancer cells change their cell adhesion properties to allow them to survive and form more tumours. Our laboratory discovered that a molecule called “Liver Kinase B1” (LKB1) and its downstream target, NUAK1, enables ovarian cancer cells to survive these stressful conditions using different strategies to generate energy. The loss of these two molecules leads to a decrease in a cell adhesion molecule called β5 integrin. My work focuses on taking a closer look at the change in cell adhesion properties in ovarian cancer because they are a critical aspect of metastasis. Currently, I am using different functional assessments to determine the roles of β5 integrin in cell adhesion and spheroid formation. Understanding how ovarian cancer cells alter their cell adhesion to allow for metastasis may reveal unique vulnerabilities that could improve treatment outcomes for ovarian cancer patients.

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