PHD, Kent State University, 2007, College of Biomedical Sciences

Tumor cell invasion is a complex process that involves coordinated functions among several cellular processes including adhesion, migration and proteolysis. Key mediators of the invasion process are the urokinase plasminogen activator receptor (uPAR) and integrin a and b subunits. A model system of breast normal epithelial and invasive breast cancer cells with discriminate invasive capacities (minimal, moderate, and high) was used to evaluate the cells within a variety of indigenous extracellular matrices (ECMs). Morphologic features were characterized and compared for the cells under conditions of normal growth and to promote invasion (treatment with phorbol myristate acetate). Production levels of uPAR and integrin subunits (alpha2, alpha3, alpha5, alpha6, alphav, beta1, and beta3) were measured by Western blot analysis. Molecular associations between uPAR and integrin subunits were identified using co-immunoprecipitation. Comparisons of the cells under conditions of normal growth and promotion of invasion, morphologic differences were observed and correlated with the cellular invasive phenotypes. Significant increases in the numbers of rounded cells were indicative of the phenotype for the moderately and highly invasive cells. Transformation to a rounded morphology corresponded with a predominant decrease in the production of integrin a and b subunits. Assessment of the interactions between uPAR and integrin subunits revealed that the receptors were covalently associated. The covalent associations were determined to be through cysteinyl disulfide bonding since the thiol reducing agent beta-mercaptoethanol disrupted the interactions and generated integrin fragments. Increased levels of uPAR-integrin associations were prevalent for the invasive breast cancer cells in comparison to the normal breast epithelial cells. UPAR-integrin associations were influenced by the ECM substrates, most notably on vitronectin due to a vitronectin-binding site on uPAR. Decreased prod (open full item for complete abstract)

Committee: Kathleen Doane (Advisor) Subjects: Biology, Cell