It can be argued cogently that the infiltration of contiguous and distant regions of normal brain by astrocytoma cells from the primary tumor is a major cause of treatment failure in patients with this disease. To enhance our understanding of the molecular mechanisms underlying astrocytoma cell invasiveness, we previously performed a partial characterization of the ECM of the human brain,26,27,46,47,51 examined the contributions of matrix metalloproteinases and tissue inhibitors of metalloproteinases in astrocytoma invasion models in vitro,5,35,36,49 and studied astrocytoma adhesion to the ECM through an analysis of integrin and focal adhesion kinase expression.50 Work in this field has been hindered by two main factors: first, previously described and currently available in vitro invasion models do not take into consideration the unique representation of ECM macromolecules in the brain; and second, unequivocal identification of tagged and nonperturbed human astrocytoma cells within the selected model of brain tumor invasion has not been consistently achieved.
To overcome these difficulties, we have modified existing organotypical models of cultured rodent brain tissue to establish a reproducible and relevant model for human astrocytoma cell invasion. In addition, we have labeled human astrocytoma cells with GFP, which serves as a reporter molecule for monitoring astrocytoma cell invasion in our model. Finally, to determine whether this model is useful in measuring differential migratory rates among astrocytoma cells, we have cotransfected human astrocytoma cells with a cDNA for RHAMM17,18,56,57 as well as GFP. In this article we show that RHAMM-transfected human astrocytoma cells invade human brain tissue to a greater extent than control tumor cells, and that the degree of this invasiveness is both quantifiable and reproducible.
We thank Eva Turley for the RHAMMv4 cDNA.
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This work was supported by the Canadian Institutes of Health Research (CIHR), Brainchild, and the Research Institute, The Hospital for Sick Children. Dr. Rutka is a recipient of a Scientist Award from the CIHR. Stacey Ivanchuk is a recipient of a fellowship award from the National Cancer Institute of Canada. Dr. Jung was supported by a research grant from the Korean Research Foundation.