Understanding and Predicting Cancer Cell Aggressiveness From Their Migratory Phenotypes

Cell migration is an integral process for diverse physiological and pathological processes, including embryonic and tissue development, wound healing, immune response, chronic inflammation and cancer metastasis. Cancer metastasis, a coordinated and complex multistep process by which tumor cells disseminate from primary tumors to secondary sites, is responsible for up to 90% of all cancer-related death. During metastasis, tumor cells must interact, migrate and navigate through considerably different microenvironments including tissues at the local and distal sites, as well as within the circulatory system. As such, enhanced cell motility has been widely associated with increased cancer aggressiveness and metastatic potential, and overall poor patient outcome. A thorough understanding of the biochemical and physicomechanical driving forces underlying cell motility can therefore provide critical insights for the development of novel and effective diagnostic, preventative, therapeutic and prognostic strategies against cancer. We start by first examining the role of podocalyxin on the migratory behavior of pancreatic cancer cells. The sialoglycoprotein podocalyxin is absent in normal pancreas but is overexpressed in pancreatic cancer and is associated with poor clinical outcome. Here we investigate the role of podocalyxin in migration and metastasis of pancreatic adenocarcinomas using SW1990 and Pa03c as cell models. Although ezrin is regarded as a cytoplasmic binding partner of podocalyxin that regulates actin polymerization via Rac1 or RhoA, we did not detect podocalyxin-ezrin association in pancreatic cancer cells. Moreover, depletion of podocalyxin did not alter actin dynamics or modulate Rac1 and RhoA activity in pancreatic cancer cells. Using mass spectrometry, bioinformatics analysis, co-immunoprecipitation, and pulldown assays, we discovered a novel, direct binding interaction between the cytoplasmic tail of podocalyxin and the large GTPase dynamin-2 at its GTPase, middle, and pleckstrin homology domains. This podocalyxin-dynamin-2 interaction regulated microtubule growth rate, which in turn modulated focal adhesion dynamics and ultimately promoted efficient pancreatic cancer cell migration via microtubule- and Src-dependent pathways. Depletion of podocalyxin in a hemispleen mouse model of pancreatic cancer diminished liver metastasis without altering primary tumor size. We next apply our knowledge of cell migration to develop a device for glioblastoma prognosis. Glioblastoma is the most aggressive form of brain cancer, characterized by high recurrence and dismal prognosis. Presently, there is no effective in vitro platform that can rapidly measure complex cellular phenotypic traits and accurately predict patient-specific clinical outcomes. Here, we employed a proprietary in vitro testing platform, Microfluidic Invasion Network Device (MIND), and screened a panel of 22 patient-derived primary glioblastoma specimens in a blind manner. We evaluated the ability of glioblastoma cells to navigate and squeeze through confined microenvironments that mimic in vivo tight perivascular conduits and white matter tracts in the brain parenchyma, as well as the proliferative capacity of highly motile subpopulations. By combining migratory- and proliferative-based indices, MIND predicts progression-free survival (p=0.008) and time to recurrence (p=0.006) retrospectively with high sensitivity (85%), specificity (89%), and accuracy (86%). In a pilot prospective study, MIND classified all patients accurately based on their survival outcomes. Overall, this dissertation illustrates the importance of studying cell migration, both at the basic science as well as the translational levels, to better understand the mechanisms of cancer aggressiveness and develop potentially useful clinical applications