INTEGRIN ACTIVITIES DURING TUMOR PROGRESSION BY GALECTIN-3

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The proposal seeks to establish the significance of galectin-3 in integrin functions during malignant progression of breast and prostate carcinomas. The progression of tumors if normally accompanied by the alterations in the interactions of the transformed cells with extracellular matrix proteins, such as increased invasiveness and motility. These processes are regulated by integrins, which are in turn modulated by other cellular proteins. The ability of integrins to interact with galectin-3 prompted us to question the biological significance of this association. Specifically, we are interested in testing the hypothesis that the expression of galectin-3 is necessary for the modulation of the activities of integrins responsible for cell to extracellular matrix interactions. The study is designed to; a) determine the importance of galectin-3 in cell to extracellular matrix interactions, b) demonstrate that galaectin3 is a critical molecular partner of integrins which regulate their functions, c) to identify integrin heterodimers which associate with galectin-3 in the breast and prostate carcinomas and d) to analyze the interaction of galectin3- expressing and null expressing cell lines including those transfected with antisense oligos, with bone and lung extracellular matrices. Antisense DNA technologies will be employed to disrupt galectin-3 gene expression in the carcinoma cells. The interaction of cells with the diminished galectin- 3 expression (antisense transfectants) as well as sense and vector transfected controls with extracellular matrix proteins will then be monitored in vitro. It is expected that lack of galectin-3 expression will result in diminished interaction of these cells with the extracellular matrix proteins. The interactions between purified galectin-3 expression will result in diminished interaction of these cells with the extracellular matrix proteins. The interaction between purified galectin-3 and integrins, particularly alpha 1 beta1 will be analyzed by light scattering methodology to obtain binding parameters. Using fluorescence activated cell sorting techniques (FACS(, we will seek to determine whether galectin-3 alters the expression of specific cellular integrins. Using a simplified galectin-3/integrin binding assay, we will determine how galectin-3 modulates the binding interaction between alpha1 beta1 integrins and laminin-1. We will also determine how the modifications of the biological functions of galectin-3 affects its interaction with integrins and vice vera. Immunoprecipitation methodology and confocal laser microscopy will be used to identify integrins which are associated with galectin-3 on the surfaces of the breast and prostate epithelial tumor cells. Lastly, the adhesion potential of galectin-3 expressing and null expressing cells to bone extracellular matrix and to lung tissue secretions will be evaluated. Both breast and prostate carcinoma cells preferentially metastasize to the bones and to a lesser extent, the lungs. These studies will provide new avenues which may be exploited for the control of the dissemination and growth of metastatic breast and prostate tumor cells.