| Epithelial ovarian cancer (EOC), the most lethal gynaecological cancer, is typically detected after metastasis within the peritoneal cavity has occurred. While early stage EOC is curable, metastatic disease is generally fatal due to eventual development of chemoresistance. Using a panel of six ovarian cancer cell lines, my studies focus on elucidating mechanisms contributing to ovarian cancer cell invasive behaviours, in attempt to reveal new therapeutic targets. Matrix degradation and motility are important contributors to peritoneal invasion. Evaluation of Matrigel and collagen I matrices as representatives of basement membrane and stromal matrix barriers respectively, revealed the inadequacy of Matrigel, which cells penetrated in absence of matrix metalloprotease (MMP) activity. Collagen I was therefore used in subsequent invasion studies. MT1, a transmembrane MMP with potent pericellular proteolytic activity, was determined to be a critical mediator of collagen I matrix degradation and invasion by ovarian cancer cells, and its ectopic expression conferred an invasive ability to previously non-invasive cell lines. Although cells that expressed MT1 were generally more motile, MT1 did not impact cell motility. The formation of multicellular spheroid aggregates within ascites fluid enhances ovarian cancer cell resistance to apoptosis. Spheroid formation and invasion were examined in 3D culture. A striking correlation was evident between capacity for compact spheroid formation and cell penetration of 3D matrices. This suggests invasive cancer cell behaviours promote spheroid formation such that an invasive sub-population may acquire preferential survival/resistance to chemotherapeutics. Contractile behaviour and a mesenchymal phenotype were characteristics common to the invasive, spheroid-forming cell lines. In this 3D culture model, although MMP activity was required, additional factors related to cell motility appeared to limit invasion. Proteomic profiling of the cell lines was performed to reveal factors contributing to the divergent motile capacities. Several proteases, integrin subunits, and proteins mediating actin cytoskeletal dynamics were upregulated in the motile cell lines. Pathway analysis suggested an upregulation of integrin and actin cytoskeletal signalling pathways in the invasive, spheroid forming cells. Together, these data emphasize the importance of targeting ovarian cancer spheroids, and have revealed MT1 and actomyosin contractility as potential contributors to ovarian cancer metastasis. |
