The major goal of these studies is to define the functions of laminin (LMN) relative to tumor cells. Additionally, molecular characterization of """"""""domains"""""""" within the laminin molecule is being addressed. Monoclonal antibodies have been generated and additional ones will be created that will recognize unique epitope determinants on the LMN molecule. This will permit us to fragment the LMN molecule using various proteases and determine domains that bind to: (1) monoclonal antibodies; (2) type IV collagen; and (3) heparin. Following this, molecular characterizations of these peptides using two-dimensional gel electrophoresis will be performed. Studies in other systems suggest there may be unique biochemical attributes of certain regions of the molecules that subserve charge/charge interactions which may occur in the basement membrane or cell matrix. Further biochemical characterization of the LMN subunit chains is necessary and studies are progressing to reduce, alkylate, and separate the 200 and 400 chains of LMN from the murine EHS tumor. Studies are asking whether each chain can subserve cell adhesion of tumor cells binding to heparin or other activities. Additionally, a number of studies are evaluating a fundamental aspect of metastatic cells: their ability to migrate. These studies are being performed in vitro using blind well chambers to determine whether laminin and laminin fragments promote the migration of tumor cells. Tumor cell migration can be characterized in four different forms falling into two groups. One is due to fluid phase or soluble attractant which is gradient-mediated chemotaxis or the migration of cells without a gradient chemokinesis. The second is due to migration of cells to a solid phase substrate-bound attractant with a positive gradient-haptotaxis, and without a gradient-haptokinesis. Further studies will use monoclonal antibodies, peptide fragmentation, and affinity purification to isolate regions of the molecule that might promote migration of cells. We feel this is an extremely important study because it may permit us to understand a crucial factor governing the migration of tumor cells in the metastatic process. (A)
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