Increases in expression and activity of matrix-degrading enzymes such as the cysteine proteinases cathepsins B and L, and abnormal levels of their inhibitors, the cystatins, are associated with tumor cell invasion and metastasis. Environmental conditions have been shown to be causative factors in the development of a metastatic/invasive phenotype. We hypothesized that cell-matrix interactions affect the expression and activity of cathepsins B and L and their inhibitors in the prostate cancer cell lines, PC3 and DU145. To test this possibility, PC3 and DU145 were plated on uncoated surfaces or on surfaces coated with the reconstituted basement membrane, Matrigel. The cells were analyzed for cathepsins B and L immunolocalization, protein expression and activity 48 h after plating. Our data demonstrated that cathepsins B and L displayed a distinct punctate distribution with little co-localization; individual cells displayed a predominant staining for one or the other enzyme. Cathepsin B had a perinuclear distribution in PC3 grown on uncoated surfaces but a more peripheral staining in PC3 plated on Matrigel. Localization of cathepsin L remained predominantly perinuclear regardless of the plating surface. In addition to the translocation of cathepsin B from a perinuclear distribution to the cell periphery, growth of PC3 on Matrigel shifted cathepsin B activity from the cell extract to the media. There were no significant changes in cathepsins B and L immunolocalization or activity in DU145 with regard to plating surfaces. Likewise, the activity of endogenous cysteine proteinase inhibitors (CPIs) and protein expression of cystatin C remained unchanged in both cell lines. In conclusion, the interaction of PC3 prostate cancer cells with extracellular matrix components affects the distribution of cathepsin B protein and activity.

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