Role of the protein C system in breast cancer cell invasion and endothelial cell angiogenesis

Cell migration is involved in multiple processes including development, angiogenesis, and cancer invasion. Various receptors, signaling pathways, and extracellular proteases all work in concert to promote cell motility. Stimuli cause cells to move, including soluble chemoattractant and extracellular matrix-bound molecules. Two examples of cell migration, cancer cell invasion and endothelial cell angiogenesis, are explored further in this Dissertation.; Serine proteases have key roles in coagulation. Some proteases have non-hemostatic functions related to regulation of inflammation, apoptosis, and cell migration. Activated protein C (APC), anticoagulant serine protease, is also involved in regulating such cellular functions. However, it is unclear which receptors, signaling pathways, and/or extracellular proteases are involved in the mechanism utilized by APC to regulate cell motility. I tested a hypothesis that APC increased cell migration of breast cancer and endothelial cells through similar interdependent extracellular and intracellular processes. I studied the mechanism of how APC promoted cell motility using MDA-MB-231 breast cancer cells in chemotaxis and invasion assays and using human umbilical vein endothelial cells in angiogenesis assays.; APC increased breast cancer and endothelial cell migration. For breast cancer cells, increase in migration was concentration dependent. Endothelial cells responded to an optimal APC concentration, closer to physiological protein C levels. Only active APC increased cancer cell migration and endothelial cell tube formation. APC-increased cell motility was also dependent on binding endothelial protein C receptor, and activating protease activated receptor-1 and epidermal growth factor receptor (EGFR). Through these receptors, APC activates phosphatidylinositol 3 kinase (PI3K) and mitogen activated protein kinase pathways to increase cell migration. Extracellularly, APC does not interact with urokinase and plasminogen activator inhibitor-1. Instead, APC-promoted invasion involves degradation of the extracellular matrix (ECM) by matrix metalloprotease-2 (MMP-2) and -9. Inhibition of any component of this mechanism completely abrogates the effects of APC. In ex vivo aortic ring assays, active APC increased the formation of endothelial sprouts around the aortic section periphery. Similar to cancer cells, APC increased sprout formation through activation of EGFR and PI3K, along with degradation of the ECM through MMPs. Collectively, APC increases breast cancer and endothelial cell migration through similar interdependent extracellular and intracellular pathways.