Tumor invasion is potentiated by adhesive interactions between tumor cells and extracellular matrix proteins. We have recently demonstrated that vitronectin is a marker of the most malignant glial-derived brain tumor, glioblastoma multiforme (GMB), and as a matrix protein potentiates adhesion in these tumors. More recent data suggest vitronectin is expressed at the invading tumor margin in a nude mouse model of GBM tumors, suggesting a role for vitronectin in GBM tumor invasion of normal tissue. Therefore, the overall objective of this research is to characterize the molecular mechanism(s) of vitronectin adhesion in GBM tumors, and to develop more effective means for the diagnosis and prognosis of these tumors. This proposal will focus on four specific goals. First, to determine whether vitronectin is synthesized by human GBM tumor cells in situ and in vitro, using in situ hybridization, Western blotting and immunoprecipitation analysis. Second, to characterize the vitronectin receptor integrins expressed on GBM tumors in situ and on cultured cell lines, immunohistochemical and immunoprecipitation analysis will be performed, with probes to the three known vitronectin receptor integrins alphavbeta3, alphavbeta5 and alphavbeta1. Third, inhibition of the adhesive and invasive function of the vitronectin receptor integrins on GBM cells in vitro will be studied, based on reports of their modulation on other cell types by cytokines and growth factors, followed by immunoprecipitation and Northern blot analysis. Fourth, the role of the alphav and beta3 integrin subunits in the malignant phenotype of GBM tumors will be determined. An alphav negative GBM cell line will be selected by fluorescence-activated cell sorter analysis and a non-tumorigenic beta3 negative GBM cell line will be transfected with the beta3 gene, followed by in vitro and in vivo growth and adhesive property studies of both cell lines.
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